EP0713661A1

EP0713661A1 - Raised up furniture having flat parts supporter

Info

Publication number: EP0713661A1
Application number: EP94913622A
Authority: EP
Inventors: Jorge Escatllar Zunzunegui
Original assignee: Individual
Current assignee: ESCATLLAR ZUNZUNEGUI, JORGE
Priority date: 1993-04-27
Filing date: 1994-04-26
Publication date: 1996-05-29
Anticipated expiration: 2014-04-26
Also published as: AU6570294A; ES2131192T3; DE69416312T2; DE69416312D1; JPH08511178A; EP0713661B1; CA2166187A1; DK0713661T3

Abstract

High piece of furniture, such as table, chair, writing desk, cart, stool, etc., whose support structure or framework is fabricated with planar parts (18), having slender proportions in planes (2) intersecting at axes (1) which are vertical or slightly inclined, and defining open volumes. Said planar parts are shaped like legs, arms, and the like, and are fabricated from boards, planks which are cut out into said shapes, or from materials compressed in planar molds, such as in a press. In both cases, the material used may be wood fiber of medium density (F.D.M). The planar parts may be joined by using glue, excentric nuts, screws and special parts. The use of screws (17) together with special parts (16) makes the piece of furniture dismountable, including the padding (24) and the upholstery (25) whose covers are removable.

Description

Field of the invention

The present invention relates to furniture of the kind of tables, chairs, serving trolleis, writing desks, and other raised up furniture. The supporting structure in such pieces of furniture is constructed of flat parts that allow new ways of manufacturing and assembly. The invention includes the methods of design and manufacturing of the flat parts and the fixed or detachable unions for such parts. The preferred material used in the development of this invention is the Medium Density Fiber ( MDF).

Backgrounds of the invention

In raised up furniture, like tables or chairs, there can be considered to be some supporting structures in vertical planes, like the legs and arms, and some structures in horizontal planes, like the board in a table or the seat and armrests in a chair.
The supporters in this furniture are usually constructed of solid wooden laths which strong grain is oriented along the lath. From the laths some elongated parts are manufactured, some to be useful as supports in a vertical position and others for making the whole rigid in a horizontal position. The supporters thus constructed are rarely organized with its parts inclined or in open volumes, as it would be in the case of a wooden tripod, and are limited to parts having elongated proportions and slight curvature. The laths can be artificially curved but it is expensive. A flat part of solid wood breaks easily if the stress applied to it does not follow the direction of its grain. For this reason this furniture is not manufactured with numeric control machines that would automatically cut out the parts from a wooden wide plank or board by following appreciately curved patterns. According to the present invention some different models have been successfully constructed from wooden medium density fiber useful to be manufacture with said machines.
Some supporters are constructed after open volumes and having their parts manufactured in injection forms, in which usually melting aluminium is injected. Forms compressing non-melting materials to shape the parts are not in use for the moment. In order to use them the parts should be substancially flat, even in their union portions, because the forms would work like a press that compresses the material between two surfaces being more or less flat.
The pieces of furniture which supporters are composed of vertical planes intersecting at a sole axis are unstable by definition under gravity loadings.
It is like that because when a tangential force (F) is applied to a table board (horizontal plane), it causes a turning of that board round the axis (1) that brings along a twisting of the upper part of the vertical planes in relation to the lower parts of those planes, that is to say, a warping and a leaning of the planes (see Figure 1). To avoid this turning tendency of the table board, tables are designed in a way that the planes do not cut each other in a single axis, in other words, in a way that they do not define open volumes but closed volumes.
And so, in a horizontal cut across the legs, they define closed figures of the kind of a square (the case of a square table with four legs in the corners), of a triangle (table which base is a three planes prism), etc.
Most of the furniture nowadays constructed with flat parts are based on square, triangular or trapezoidal parts that are put together following closed volume organitations as cubes, prisms or piramids that are the ones to assure the rigidity of the assembly (see Figure 2). Due to its handicap, in very few cases these structures are organized following open volume schemes. In the case referred to by the present invention, they define open figures of the kind of crosses, stars, or segment chains (see Figure 3).
Some examples can be cited of different solutions already used within the state of technique:

* Table of piramidal support built of flat parts, which support is a piramid with arms in it designed by Oscar Tusquets for Casas firm (see Figure 4). The structure of this table consists of four vertical planes intersecting at a central axis and other four planes that form a piramid (closed volume) just to avoid turning of the vertical planes. This solution is not useful for small tables or chairs. This table is shown published in " The International Design Yearbook 87/88 " edited by the english Thames and Hudson.
* Table which frame is formed by a nucleus and four metal legs designed by Vicent Martinez for Punt Mobles (see Figure 5). In this case, the solution tends to reduce the use made of the flat parts to form just the frame nucleus and to use metal parts in places where the stresses are great, those are the legs. The way this structure behaves is similar to that of a table with a strong central axis and four legs attached to its lowest end. This table is shown published in " The International Design Yearbook 87/88 " edited by Thames and Hudson.
* Chair designed of flat parts by Sakae Kasamatsu (see Figure 6). Its frame is formed by four vertical planes intersecting at an axis. Two of them are extended up to join another two planes that form the backrest. The parts in this case do not adjust their proportions to the stresses suffered by them, that is to say, they do not get the slenderness of proper legs and arms (trapezoidal parts). This chair is shown published in " Worldwide Interiors " issued by the International Federetion of Interior Architects and edited by japanese Rikuyo-Sha.
* Table of cross-shaped support. This support made up of four vertical planes that join each other in the centre, table of which there are some models in the market (see Figure 7). The four vertical parts are in this case square and heavy. They include iron crosses that tighten them up in their upper, lower or both parts of them. They are big tables aesthetically considered as office furniture. Some of this models are shown in " Annual of Furniture Designers I and II " part of the European Masters collection edited by spanish Atrium Ediciones.

The union fittings for flat parts or pieces of board being nowadays on the market, are the kind of:

a. cylindric pieces having a single drill in which a screw is fixed, and
b. eccentric nuts that house a single spigot.

There are various covers for stools and bathroom fittings in the market that are fixed by having an elastic sewed along the edge of the towell cloth. They are not used however, for upholstered and padded furniture because they are not enough stable or aesthetically pleasant when mounted.

Description of the invention

The object of the present invention is to provide raised up furniture which supporting structures consist of flat parts, and its methods of design and manufacture. More exactly, furniture in which its usable surfaces and volumes are raised up on flat parts having proportionate shapes that are put together in vertical or slightly inclined axes in a way that they define open volumes. It is the outline of said flat parts what imprints character to the piece of furniture, that is to say, it follows the shape of some legs, some arms, etc., in a certain style.
In other words, the present invention consists in a way of producing furniture of the kind of tables, chairs, writing desks, serving trollies, stools, etc., in which the supporting structure or frame is constructed of flat parts that are arranged after open volumes.
The present invention includes some improvements that offer numerous advantages in manufacturing, using and marketing of this kind of furniture, advantages that are compiled at the end of this chapter.

Method of Design and Materials

It is meant that the supporting structure or frame is the part of the piece of furniture designed to support the usable surfaces or volumes in it. That is to say, to support the board of a table, the arm and back rests of a chair, or the drawers of a writing desk.
Thus, the supporting structures that are described according to the present invention can have, depending on different models, three basic embodiments:

* vertical flat parts that are joined together in the axes to form the supporter on which the other portions of the piece of furniture rest,
* vertical flat parts placed separately from each other and that are joined to another parts of the piece of furniture, like the board in a table or the seat in a chair, and
* a combination of the two preceding embodiments.

In all cases, behavior and difficulties regarding the structure are the same. The invention therefore focusses on the design and manufacture of the vertical flat parts that altogether raise up the other portions of the piece of furniture from the floor. According to this, the supporter of the piece of furniture is considered to be formed by the flat parts and their union means.
The flat parts composing the structure are designed adjusting them to the stresses that could appear in each section of the part, giving to every section the minimum size that is possible for a normal use of the furniture. In other words, the parts have proportionate shapes.
In the following, the criteria used in designing the supporting structures and the flat parts that constitute them are expounded:
The supporting structures should occupy as little of space as possible and have a shape to make them practical and nice. In order to make compatible these requirements with the condition of using flat parts in its construction, it has been resorted to the following composition scheme (see Figures 8 and 9):

a) To choose a certain number of vertical planes that according to different cases can be slightly inclined (2).
b) To orientate the planes in a way that they point from the centre of the furniture towards its borders, as the radials do in a circumference. This makes using of the furniture easier, for we will find the parts are settled pointing at us edgeways, and therefore occuping less of room.
c) To make the planes get together in a single axis (1) in the case of round furniture, square one, or the like (as it is in the case of a round table or a chair). Or get together in more than one axis if the furniture has elongated proportions. Each axis (1) can generate then a separate supporter, or else be all of them put together forming a chain (see Figure 10).
d) To draw in the planes the shape of the parts that will fit the best with the type of furniture and its use. Following Figure 11 we shall draw the outlines of the parts in this way:
d.1) Defining the generally straight and horizontal parts (4) designed to support the usable surfaces of the furniture (table board, chair seat, etc.), and those designed to support the whole piece of furniture (base of the legs).
d.2) Defining the straight portions (3) of the outline designed to be joined to the other parts in the axis (1) if this union is necessary to make the whole rigid.
d.3) Joining the preceding segments by adding generally curved lines (5) between them until the drawing of the part outline is completed so that the sections in every portion of the part are big enough to resist the stresses.

The construction of the supporting structure by following the preceding composition scheme generates a series of problems in its behavior, as they were previously exposed, that makes it unstable under tangential forces applications. The turning round the vertical axis produces a torsion and an excesive warping of the parts (see Figure 1). For solving this problems the following strategies have been used (see Figure 12):

a) To accumulate the material round the axis (1) where the parts are joined together, thus forming a rigid nucleus (6).
b) Starting from this nucleus, the material must be extended in the appropriate directions (7) to form the supporting extensions, as if some legs, arms, or brackets, always following the various planes (2) that depart from the axis towards radial directions.
c) The appropriate directions (7) to which the preceding label refers are those that, as much as possible, tend to be radial to the nucleus within the plane (2) of the part.
d) To give the nucleus (6) a size big enough in relation to the lengh of the legs and of the arms so that it can be considered as rigid with regard to them.
e) The nucleus can have an appreciately smaller size (6') in the case that it was solidly joint to other parts like a table board, a chair seat (8), etc. (see Figure 13). And even to be entirely constituted by said parts, in which case the vertical flat parts do not meet each other in the axis (1)(see Figure 29).
f) To design the union between the parts in accordance with the material and the model, giving it the most appropriate shape so that it could resist the different strains in it.
g) The legs must tend in its whole to define pointed arches or parabola (9) (see Figure 14). This makes them to guide the loadings down better and at the same time to get advantage of the arch effect. To enlarge this arch effect some non-slipping material sheets (10) can be added to the base of the legs.

Up to here, we have been studing the most favourable basic shape for all the supporting structures in general. The resistance and rigidity final rate of the structures will depend for each particular model on the following factors:

a) The way the final shape of the structure would approximate to the most favourable basic shape already described.
b) On the characteristics of the material used.
c) On the characteristics of the union used between the parts.
d) On the thickness chosen for the parts.
e) On the width given to each section of the parts in proportion to the stresses supported by them. In the following, each of the preceding labels, but a), are expounded in detail:

b) Characteristics of the material used.

Due to its flat shape, the parts can be fabricated by cutting them out from boards or planks, or as well be fabricated in forms.

b.1) There are many different industrial materials available board or sheet shaped that can be used in manufacturing the parts: wooden Medium Density Fiber board (MDF board), plywood, wooden striped panel, sandwich panels of different materials, glass, marble, metal or plastic sheets, etc. Exept for the last one, all of them are ecological. The MDF board is edge mouldable, economic, recyclable and allows to use light kinds of wood in its composition, thus avoiding unnecessary felling of forests of noble kinds of wood. From all this, it is deduced the importance of directing the present invention towards manufacturing the furniture from Medium Density Fiber board (MDF board) as a prior material.
Almost every of the models developed up to this moment, of which most are illustrated in the Figures, have been successfully manufactured from MDF board. This has been possible by making good use of the characteristics of the material in the following way:
The MDF board composition is quite homogeneous in all of its extension and among different board sheets, this makes them reliable in its behavior during the manufacturing process and afterwards in the use of the furniture. The MDF board is composed of a bed of very thin wood fiber, or similar, that is compressed to a thickness 20 times smaller than the original. This high compression makes the fiber to get more compressed in the board portions next to the outward faces, thus making these portions to be stronger than the intermediate portion. Increasing the thickness of the board we get those portions to be thicker and to be more separated from each other, this increases considerably the strengh of the board against bending stresses. The union between parts will be made rigid by coupling screws with said strong portions near the outfaces, as it will be seen further on.
b.2) Therefore, it comes out to be very advantageous that the stronger and heavier material would accumulate in the outer portions, in this way the parts gain in strengh without increasing its thickness or weight. For this reason, another specially useful boards are the plywood or sandwich panel, preferably having the portions nearest to the outward faces more strong and the intermediate one more light.
b.3) The materials that are nowadays elaborated in forms within furniture manufacturing are aluminium and some different plastics. Forms in which these materials are injected melting for them to take the shape of a certain part. Through this method a great freedom is obtained in shaping the parts, that moreover do not need almost any finishing touches to be completed.
The present invention allows us to manufacture in forms the parts that compose the supporting structure of the furniture by consuming materials that cannot be melted, like Medium Density Fiber (MDF). Due to the flat shape of the parts, forms can be used in between of which the fiber is compresed by following a process similar to that of the board production. The parts thus shaped in forms out of MDF have similar characteristics in everything to those made from board of the same material, with the advantage that its sections (11') can have slightly varying thickness (see Figure 16).
b.4) It is not rejected the possibility of using and investigating new materials, or composing them from the already existing, as may be the inside reinforcing of the MDF parts with wire nets or some long fiber next to its outward faces. Or the interior lightening of the parts with different materials.

c) Characteristics of the union made between parts.

The union between parts that form the supporter can be made in the following ways:

c.1) permanent by sticking them up, generally with epoxy resin, and the possibility of reinforcing this union with spigots.
c.2) Pernanent by sticking the parts up and holding them together with eccentric nuts, or the like, for facilitating the assembly.
c.3) Detachable by screwing them up with cylindric pieces (16) and (22), or pieces having other shapes (30) and (31), that are embedded in the parts to be united (see Figures 27 to 35). This union is strong enough so as the vertical flat parts do not need in some models to be joined together in the axis (1)(see Figure 29).
c.4) Through intermediate pieces that facilitate the union or add something to the aesthetic expression of the furniture, like wooden axes, brass, aluminium, etc.(1')(see Figure 34), or like intermediate plates (21) (see Figure 28).
c.5) Through intermediate parts that facilitate the folding of the supporter, as various hinges.
c.6) Through telescopic guides (15) to form extensible supporters (see Figure 21).

d) Thickness chosen for the parts.

Depending on the manufacturing method, the thickness of the parts can be:

d.1) The same throughout the width of every section (11) of the part, when it is fabricated from board or sheet (see Figure 15).
d.2) Slightly varying throughout the width of every section (11') of the part, when it is fabricated in compressing forms (see Figure 16).

The most recommendable thickness for manufacturing of tables and chairs from Medium Density Fiber board are:

30 mm. in most common cases.
35 mm. if a special rigidity is required.
19 mm. in case they were little or auxiliar furniture.

These measures are cited as a reference for they are nowadays usual board thickness in the spanish market.

e) Widths chosen for the different sections of the part.

The width in each section is the minimum needed to resist the stresses that can appear in it, that is why the resulting parts are proportionate-shaped. We can choose between two design strategies previously to determinating the width of the sections, and those are that the parts can have a solid shape or have holes interior to its outline, that is to say, they can be of:

1) Unitary outline (see Figure 24).
2) Exterior (12) and interior (13) outlines (see Figure 23), that allows to obtain lightened parts and triangulated structure ones.

In the following are described in detail the ways in which furniture can be made detachable and the pieces that can be used for it:
The furniture can be made detachable by using some cylindric pieces (16) that are embedded in the flat parts that form the supporter. In said cylindric pieces are turned the screws that join the flat parts to the other structures of the furniture (see Figure 27).
The cylinders are placed with its main axis at a right angle to the plane of the part and has at least two threaded drills placed across the axis and near the heads of the cylinder. In them are turned the screws (17) that are then near both outfaces of the flat part and that assure transmitting the stresses that concentrate in them, specially in the case of the Medium Density Fiber (MDF) as seen before. The lengh of the cylinder is the same as, or approximately, the thickness of the part in which it is fitted and its diameter depends on the compressive strengh of the material in which it is fitted, being recommended in general the use of 15 mm. or bigger diameters with MDF.
The screws can fix the flat part to the horizontal structure (19) of the furniture directly (see Figure 27) or through an intermediate plate (21), that in the case shown in the figure is metallic (see Figure 28). The horizontal structure (19) can also be subdivided as kind of intermediate plates that are screwed up to the top board (see Figure 40-b y 40-c).
All these methods can also be used for joining the flat parts to non-horizontal structures like the backrest of a chair.
Joining of the parts through cylinders is strong enough so that, in some models, there is no need of joining the flat parts to each other to form a nucleus. In these cases another structure of the furniture, generally the seat of a chair or the top of a table, is the one to act as a nucleus (see Figure 29). A turning of the supporter round the central axis (see Figure 1) produces in this case stresses on the horizontal structure that are smaller than those produced while bending under furniture loading, so that this bending will determine its size. In the case that the horizontal structure was a sole board of MDF, it is recommeded a minimum thickness of:

19 mm. in chairs and low tables.
23 mm. in tables smaller than 120 cm. in diameter.
30 mm. in bigger tables.

The cylindric pieces (16) to which the screws (17) are fixed can be placed on the edge of the part so that only half of the cylinder embedding is needed (see Figure 30).
Said pieces to which the screws are fixed, also can have a shape adapted (30) to the flat part in the portion of the outline where it is embedded, and preferably are to be fabricated with forms (see Figure 31).
The cylindric pieces (16) can group together two or more flat parts at the same time it joins them to the horizontal structure (see Figure 32) in a way that the resultant section is the sum of the grouped sections. The parts can have different outlines from each other elaborated in a way that when they are put together they compose a unitary design, in which the parts can be overlapped completely or just a portion of them.
The cylinder heads can be set in all cases out of sight if the drills do not get through the outface of the part, or if the cylinders are fitted and the holes are sealed up afterwards.
Another embodiment of the union that follows the same working scheme the cylindric pieces do is the one illustrated in Figure 33. Two pieces that can be equal to each other (31) have in one of their ends a cylindric portion (32) to be fitted into one of the sidefaces of the vertical structure flat part. On the other end of each piece, there is a drill, threaded rod, or the like, that allows fixing it to the horizontal structure of the piece of furniture. Both pieces are fitted one in front of the other and joined together through a threaded rod, a rivet, or the like, in a way that both pieces remain in sight.
The union between vertical and horizontal parts can be done by fitting a portion of both parts together (29) (see Figures 39 and 40) so that they need less of screws or spigots in it.
Another way of joining the parts together that is very similar to that of cylindric pieces, consists in simultaneously using of glue and eccentric nut-fittings to allow assembly of the furniture with no need of using any tools or special installations.
Joining of the flat parts (18) together round the geometric central axis (1) can be made in a way that the edge of every part meets the face of another (see Figure 34). This enlarges the contact area of the union and avoids the need of preparing the edges to be joined with any special cut. This setting is either useful when a materialized central axis (1') is placed between the parts because it enlarges the contact area or because it allows the use of fittings like the one described next.
Joining of four parts together at right angles to form the supporter of a piece of furniture can also be made detachable by having cylindric pieces and screws that do not need adding glue between the parts to form a rigid union (see Figure 34 and 35). The cylinders (22) are fitted in the parts having its main axis at a right angle to the plane of the part. They have a drill in the main axis that houses a screw (17) and another threaded drill across the axis in which another screw is turned. And so, four cylinders are joined by four screws forming a square that holds tight the parts together and round the materialized axis (1'). The recommended dimensions for the pieces of tables made of MDF board being 30 mm. thick are:

Cylinder length 16 mm.
Cylinder diameter 22 to 26 mm.
Screws diameter 6 mm.
Axis section 20x20 mm.

The screw heads can screen the sight of the cylinders or be housed inside them as seen in Figure 35, or as well be hidden, after the assembly, under a cap or finishing adhesive.
These unions round an axis can also be done with glue and eccentric nut-fittings in a way that the nuts hide the heads of the fitting-spigots in a scheme that is similar to the one before. This method is useful for joinig three parts together if some fitting-spigots that can work at any angle are used and the edges are cut at an inclination of 60 degrees. Staples can be used for reinforcing the part material round the drills made in the edges, when the material used would require it.
If even the seats and backrests of furniture of the kind of chairs and armchairs are fabricated as flat parts too, this characteristic can be used for making the padding detachable by using a board added as a padding support. This piece of board or light panel can be joined to or get separated from the piece of furniture through some fittings (see Figures 36, 38 and 39). As fittings for attaching the padded board, their can be used screws, suitcase fasteners, or wedges, being the most practical of all, the screws having wooden or non-slipping and soft touch rubber heads (26). When they are used for attaching the upholstery set to the back of a chair or so, the heads can remain partially hiding behind the backrest support (27) (see Figure 36).
Furniture upholstery can be made removable if a good use of the detachable padding characteristics is made in the following manner (see Figure 36):
To the padded board (23) a cover (24) is held tight by having an elastic (25), zipper, or tape along its perimeter and therefore can be removed for washing it or substitute it for another one. For obtaining concave shapes in the cover perimeter, little hooks can be used to fix it to the board in the places of concavity.
When the padded board is placed against the surface of another board (28) that is a part of the furniture structure, the aesthetic result for the covers can be improved by sewing the elastic (25) directly to the cloth perimeter instead of housing it inside a fold of it. The look is also improved by using elastic portions attached in both ends to opposite places of the perimeter in which this is straight (see Figure 39-f).
To get more freedom in the design of the flat parts in general, these can be fabricated in separate portions that will receive different finishing treatments and afterwards will be joined to form the whole part that is a portion of the supporter (see Figure 37). It is also useful for combining different materials or board thickness in the same part.

Advantages of the invention:

* The parts can be manufactured in an entirely automatic way thus avoiding the accidents that take place with the milling machines and band saws of current use in making this kind of furniture in solid wood. In order to get it, numeric control machines or automated compression forms are used to shape the parts, that is why they must be flat parts.
* Said manufacturing methods allow obtaining the parts having appreciately curved outlines.
* The pieces of furniture can be constructed of a little number of parts.
* Furniture can be assembled in factory or be supplied as detached into parts.
* The fittings that make the furniture detachable can be very simple and may not need any sticking-gum.
* The parts can have standard unions in a way that they can be combined to create different models.
* The parts can be produced from materials having sheet or board shape, such as the wooden medium density fiber.
* Numeric control machines can cut out, mill and sand the boards to obtain the parts, and even can make in them the drills needed to make them detachable.
* The parts can be also fabricated from plywood or sandwich panel.
* The parts are easily manufactured in forms that compress the material like a press, as in the case of compressing medium density fiber, to obtain the parts directly shaped.
* Using medium density fiber in its manufacture, strong furniture can be obtained from light kinds of wood. Said light wood is transformed into fiber that is strongly compressed to form a more robust material. In this way, the consume of noble kinds of wood and the excesive felling of those forests can be diminished.
* Material combinations can be designed, for composing the boards or feeding the forms, in a way that the parts will become lighter, economical, etc.
* The rest of the furniture structures can be manufactured in the same way as the supporting parts if convenient.
* The parts can be lacquered or veneered easily because they are detached and have flat shapes.
* The parts can be storage in little of space because they are flat and can be piled up.
* The table supporters can be made extensible and folding in specially simple ways.
* Upholstery can be easily made removable, covers like, for washing or to substitute them.
* The furniture is easy to clean because of the smooth finishing of the surfaces.
* It is robust and warm furniture like the solid wood one.
* It is also simple and of dinamic lines like the metallic furniture.
* It can be given a resistant finishing treatment to be used outdoors as an alternative to plastic furniture.

Explanation of the figures

To facilitate the comprehension of this invention, a series of Figures are included:

Figure 1: - Turning effect.
Figure 2: - Closed volume (three examples).
Figure 3: - Open volume (three examples).
Figure 4: - Table of piramidal support.
Figure 5: - Table of metallic legs.
Figure 6: - Chair of flat parts.
Figure 7: - Table of cross-shaped support.
Figure 8: - Sketch for round table support.
Figure 9: - Sketch for chair frame.
Figure 10: - Sketch for open chain support.
Figure 11: - Outline of a flat part.
Figure 12: - Nucleus and extensions in the support.
Figure 13: - Nucleus size.
Figure 14: - Arch effect in the legs.
Figure 15: - Part manufactured from board or sheet.
Figure 16: - Part manufactured in forms.
Figure 17: - Round table having opaque board I.
Figure 18: - Round table having opaque board II.
Figure 19: - Round table having glass board, top ring and stand.
Figure 20: - Elongated table having opaque board.
Figure 21: - Oval-shaped extensible table having opaque board.
Figure 22: - Low extensible table having overlapping boards.
Figure 23: - Armchair of triangulated parts and wheels.
Figure 24: - Armchair having stuck up seat.
Figure 25: - Chair on three resting points and having no arms.
Figure 26: - Writing desk on three resting points.
Figure 27: - Detachable union having cylindric piece.
Figure 28: - Detachable union having intermediate plate.
Figure 29: - Detachable small table.
Figure 30: - Detachable union having an edge-placed piece.
Figure 31: - Detachable union having a piece adapted to the shape of the edge.
Figure 32: - Detachable union for paralell parts.
Figure 33: - Detachable union having exterior pieces.
Figure 34: - Table supporter having central axis.
Figure 35: - Detachable union for table supporter.
Figure 36: - Detachable and removable upholstery.
Figure 37: - Part being composed of two portions.
Figure 38: - Detachable chair having removable upholstery.
Figure 39: - Detachable chair components.
Figure 40: - Detachable table components.

In the following are expounded the contents of the Figures that by way of example illustrate the invention:

* Figure 1 illustrates a sketch of a round table having a supporting structure consisting of four planes that meet each other in a central axis (1), and to which a tangencial force (F) is applied to the edge of the board. As a result, a turning of the upper part of the vertical planes is produced in relation to the lower part and round the central axis.
* In Figure 2 are shown the sketches of three pieces of furniture made up of flat parts which are organized defining closed volumes:
- a) Shelving or cupboard which support is a square prism.
- b) Round table wich support is a triangular prism.
- c) Chair on three legs which flat parts define a hexagonal prism and, in a horizontal cut across the legs, these define a triangle.
* In Figure 3 are shown the sketches of three pieces of furniture constructed of flat parts which are organized defining open volumes:
- a) Round table of crossed vertical planes support.
- b) Elongated table having in-chain vertical planes support.
- c) Chair on three legs. In a horizontal cut across the legs, they define a three arms cross.
* Figure 4 shows a table of piramidal support (closed volume) composed of flat parts. Four of the parts are placed in vertical planes intersecting at an axis. Other four inclined planes form a piramid that holds tight the vertical planes (model by Oscar Tusquets).
* Figure 5 shows a table of metallic legs and flat parts. Its structure is similar to that of a table having a sole central axis and legs in its lower end, in which the central axis has been substituted for a nucleus of four vertical planes (triangular parts) that meet each other in an axis (model by Vicent Martinez).
* Figure 6 shows a chair of flat parts. Four vertical planes that meet each other in an axis form the frame of the chair (open volume). Two planes make the seat and another two make the backrest (model by Sakae Kasamatsu).
* Figure 7 shows a table of flat parts having cross-shaped support (open volume). The support consists of four vertical planes that meet each other in an axis and two crosses that join them up.
Corresponding to the present invention are the following Figures:
* Figure 8 shows in perspective view the sketch of a table supporting structure made up of four flat parts. The parts are placed in vertical planes intersecting at an axis (1). The planes (2) are placed at 90^º to one another defining open volumes.
* Figure 9 shows in perspective view the sketch of a chair supporter made up of three flat parts. The parts are placed in vertical planes intersecting at an axis (1). The planes (2) are placed at 60^º to one another defining open volumes.
* Figure 10 shows in perspective view the sketch for the structure of an elongated table. The parts are placed in vertical planes intersecting at three axes (1) forming a chain that defines open volumes. The projection of the supporting structure in a horizontal plane define the figure of a segment open chain.
* In Figure 11 we can see in a side elevation the different portions of the outline of a supporter flat part, being drawn in the plane of the part (2) that will cut other planes in the axis. The right vertical side of the square represents the axis (1) in which the part will be set. In this axis is placed the straight portion of the outline designed to be joined to the other parts if necessary (3). In the top and bottom sides of the square are placed the straight portions designed to support the usable surface of the furniture and the whole of it on the floor (4). Inside the square we can see the generally bending portions (5) of the part outline that join together the preceding portions.
* Figure 12 shows in perspective view the sketch of a structure having three legs made up of three flat parts placed in vertical planes (2) that join each other in an axis (1), and therefore, defining open volumes. This sketch shows the most suitable shape the flat parts that compose the structure should take to make its behavior the best with a minimum of material. The material must be accumulated round the joining area of the parts to form a rigid nucleus (6) from which depart radially the material extensions that form the legs and arms of the supporting structure, following in this manner the most appropriate directions (7).
* Figure 13 shows the front elevation of a three legs chair which frame consists of three flat parts placed in vertical planes that meet each other in an axis, and therefore defining open volumes. This sketch shows how the nucleus size can be appreciably reduced (from 6 to 6') when the vertical parts are solidly joined to another part of the furniture rigid enough for it, in this case the seat of the chair (8).
* Figure 14 shows the elevation of the supporting structure of a table composed of four flat parts that are joined to each other in an axis (1) at 90^º to one another. This sketch shows the pointed arch or parabola shape (9) that must define the flat parts forming the supporter for the legs to be the most slender possible. The arch effect can be enlarged by adding non-slipping material to the base of the legs (10).
* Figure 15 shows in perspective a part fabricated from some board or sheet that has not being edge moulded. This part has the same thickness throughout it, its faces are flat and its sections (11) have elongated rectangular shapes all of them.
* Figure 16 shows in perspective a part fabricated in forms. This part is flat as a whole, that is to say, its thickness is little in proportion to its length and width, and its guide-lines are included in a plane (see Figure 11). But its faces are not flat, its sections (11') have slightly the shape of some ellipses or lentils, thicker in the centre than in the extremes.
Examples: The following Figures illustrate some furniture models that have been developed according to the present invention and that are included as particular applications:
* Figure 17 illustrates a round table of opaque board 90 cm. in diameter, wherein a) is an elevation and b) a bottom plan view. Its supporting structure is composed of four flat parts that are put together in a vertical axis. Each part is shaped as a bracket or projecting in its upper portion that supports the table board, and in the lower portion is shaped as one of the legs.
* In Figure 18 we can see a round table of opaque board 80 cm. in diameter, in which a) is an elevation and b) a top plan view. It is similar in everything to the preceding figure except for the different style showed in the part outlines.
* Figure 19 shows a round table having glass board 80 cm. in diameter, wherein a) is an elevation and b) a top plan view. Its supporter is composed of four flat parts that are put together in a vertical axis. Each part is shaped as an arm in its upper portion that supports the table board, and in the lower portion is shaped as a leg. The table board is formed by a flat ring and a glass circle over it, both of equal diameter. The leg bases are joined to a stand (14) having a square plan.
* Figure 20 shows an elongated table of opaque board 130 x 85 cm., in which a) is an elevation and b) a bottom plan view. Its supporter is composed of five flat parts that are put together in two vertical axes. Each part is shaped as a bracket in its upper portion that supports the table board, and in the lower portion is shaped as a leg, exept for the part placed between both axes.
* Figure 21 shows an oval and extensible table of opaque board 140 x 85 cm., in which a) is an elevation and b) a bottom plan view. Its supporter is composed of six flat parts that are put together in two vertical axes. Each part is shaped as a bracket in its upper portion that supports the table board, and in the lower portion is shaped as a leg, exept for both parts placed between both axes. These two parts are identical to each other and merge together when the table is unextended. Between them there is a telescopic guide (15) that allows one of the parts to slide away from the other horizontally, thus allowing extending of the table support by enlarging the distance between the axes. The table board is oval-shaped and is divided into two halfs. When the table is extended a third rectangular board is intercalated between them. For a higher stability of the boards, the supporter can incorporate two additional brackets placed under the wider section of the board.
* Figure 22 shows a low table being extensible from 120 to 160 x 60 cm., wherein a) is an elevation and b) a top plan view. It is in everything similar to the table of the preceding figure exept for its lower height and in that the two halfs of the board have been substituted for two oval boards. These ovals are overlapping each other in a way that, when we want to extend the table, they slide one away from the other offering a larger usable surface.
* Figure 23 illustrates an armchair on wheels having triangulated parts, in which a) is a front elevation and b) a top view. The chair frame is made up of three vertical flat parts that are put together in an axis. One of the parts comprising the backrest support and the front and rear legs. The others comprising a leg and an arm each one and being placed at right angle to the central part. The three parts are triangulated having an interior outline (13), in a way for the arm and back rests to weigh down straightly onto the base of the legs through some vertical uprights. The chair can slide on some wheels mounted in the bases of its triangulated parts.
* Figure 24 illustrates a chair having arms and stuck down seat, wherein a) is a front view and b) a top one. The chair frame is made up of three vertical flat parts that are put together in an axis. One of the parts comprises the backrest support and the front and rear legs. The others comprise a leg and an arm each one and are placed at 105^º to the central part. The seat includes a thick board to which the three parts of the supporter are stuck down, so that we can get a chair of lighter parts than the preceding one.
* Figure 25 illustrates a chair on three rests and having no arms, wherein a) is a front view and b) a top one. The chair frame is made up of three vertical flat parts that are put together in an axis. One of the parts forming the backrest support and the rear leg. The other two forming a front leg each one and being placed at 60^º to the central part. The seat includes a thick board to which the three parts of the supporter are stuck down.
* Figure 26 illustrates a writing desk on three rests, in which a) is a front elevation and b) a side one. The frame is made up of three vertical flat parts that are put together in two axes. The part being placed in the centre comprises the rear leg and the supporter portion that will be settled against the wall. The other two parts comprise the front legs and the structure of the box or writing case.
The following Figures illustrate the unions that allow the furniture to be detachable and the upholstery to be removable:
* Figure 27 illustrates in detail the union between the horizontal and supporting structures of the piece of furniture. In which a) illustrates a sectional view across to the plane of the supporter part, and b) a sectional view paralell to said plane. A cylinder-shaped piece (16) and two screws (17) are embedded in the flat part of the supporter (18) to join it to the horizontal structure (19). Sideways to the screws are shown in b) two spigots (33) that enlarge the resistance of the flat part against turning round the axis of the screws. The usable surface of the furniture (20), a table top in this case, hides the heads of the screws.
* Figure 28 shows a view similar to that of Figure 27-a, in which a single board is at the same time the horizontal structure (19) and the usable surface of the piece of furniture (20). The screws (17) attach the vertical structure (18) to a metallic plate (21) that is later screwed up to the horizontal structure (19), it will generally correspond a plate to each part of the vertical structure.
* In Figure 29 we can see the elevation of a detachable table. The supporting flat parts (18) are joined to the horizontal structure (19) through cylindric pieces (16) and pairs of screws hidden in the interior of said flat parts. The top board (20) hides the screw heads. The horizontal structure is acting in this case as a nucleus (6') to the whole structure.
* Figure 30 illustrates the side elevation of a union similar to the one illustrated in the Figure 27 in which the cylindric piece (16) is embedded in the edge of the supporting flat part and the screws (17) are moved sideways in order to need only one spigot (33).
* Figure 31 illustrates the side elevation of a union similar to the one shown in Figure 30 in which the cylindric piece is substituted for another one having a shape adapted to the part shape in that place (30).
* Figure 32 shows in perspective a part of the supporting structure composed of three flat parts joined together through the cylindric piece (16) that, at the same time, joins them to the horizontal structure following a scheme similar to that of Figure 27.
* Figure 33 illustrates a perspective view of a kind of union that follows the same working scheme than the union illustrated in Figure 27 but being a different embodiment. Two exterior union pieces (31) are placed on the outfaces of the supporting flat part, and having a cylindric portion (32) fitted into it. The cylindric portions are fitted one in front of the other and joined together through a threaded rod in the case shown in the figure. The union pieces have, in the end opposite to the cylindric portion, a threaded drill in the case shown in the figure that will be useful for joining them to the horizontal structure.
* Figure 34 illustrates in perspective view a table supporter. The parts constituting it (18) are placed round a materialized central axis (1'), placed along the geometric central axis (1), that could be unnecessary if the parts are stuck together, but in general is necessary when cylindric pieces (22) are used. This scheme is also valid for 3,4,5,6 or more parts.
* In Figure 35 is shown in perspective view a detail of the detachable union of 4 parts that form a table supporter. In it, 4 cylindric parts (22) are connected to each other by 4 screws (17) forming a square surrounding a central axis (1'). Two sets like this one are enough for assembling a table supporter.
* Figure 36 illustrates the sectional view in detail of a detachable and removable upholstery. More exactly, the vertical sectional view of the upholstered backrest of a chair. The vertical support (27) holds the permanent board (28) that acts as the backrest. A second padded board (23) is fixed to the former by a screw having a wooden or rubber head (26) in a way that it is detachable. The cloth cover (24) is held onto the padded board through an elastic (25) fixed to the cloth along its perimeter, in a way that it is removable.
Examples: the following Figures refere to specific models:
* Figure 37 corresponds with the side elevation of a part composed of two different portions put together. More exactly, of one of the flat parts that form the supporting structure of a table. The upper portion has elaborated edges and can be made from solid wooden slab or be lacquered. The lower portion has flat edges and an outline of almost straight segments, thus it can be veneered in wood.
* In Figure 38 we can see the side elevation of a detachable chair. The parts of the supporting structure (18) are joined to the horizontal structure (19) through cylindric pieces (16) and pairs of hidden screws. In the same way, the backrest (28) is joined to the support that holds it (27). The upholstery covers (24) are removable by turning the heads (26) of the screws that hold the padding. Said padding hides the heads of the screws that assemble the chair structure.
* Figure 39 shows in detail the components of a detachable chair, in that a) illustrates the two of vertical parts acting as front legs, b) the two of vertical parts acting as rear legs and backrest supports (27), c) the seat acting as the horizontal structure to which the preceding parts are fixed, d) the backrest flat structure (28) that will be attached to the supports on the rear legs, e) the upholstered light panel for the seat, and f) the upholstered light panel for the backrest. The chair has partially fitting joints (29), and cylindric pieces (16) to which pairs of screws (17) are fixed in a way that the assembly is detachable. The seat or horizontal structure (19) is in this case an MDF board 30 mm. thick having holes (13) that make it lighter. The backrest (28) is an MDF board 10 mm. thick. The vertical parts (18) are of MDF board 30 or 35 mm. thick. And the upholstery light panels or padded boards (23) are of MDF board or plywood 7 mm. thick and are attached through screws having wooden heads (26).
* Figure 40 illustrates in detail the components of a detachable round table, in which a) illustrates the supporting part that acts as a table leg, b) illustrates a separate quarter part of the horizontal structure, and c) illustrates the table board. Four supporting parts (18) equal to the one illustrated in a) are partially fitted (29) and screwed (17) to four horizontal structure parts (19) equal to each other and to the one illustrated in b). These four parts are used as intermediate plates (21) for joining the supporting parts to the board that constitute the usable surface of the table (20), to which the plates are fixed through screws or any other means. The unions are similar to those used for the chair of the preceding Figure, that is to say, detachable through cylindric parts (16) to which the screws (17) are fixed.

Manufacturing methods

We have seen along the preceding chapter the way the supporters of the pieces of furniture can be designed having flat and shapely parts to be practical. In this chapter we shall see two main ways of manufacturing such flat parts and some of their variants. The two main ways are:

1) Obtaining the parts by cutting them out from board or sheet.
2) Obtaining the parts by shaping them in compressing forms.

1) Obtaining the parts by cutting them out from board or sheet:

This method lies in using materials presented in flat shape, like board, plank, sheet, etc., to cut it out by following the patterns of the parts. We shall thus obtain the parts having the desired outline and the thickness of the board from which they are cut out. This work of cutting out from the board can be done with an electric saw and some stencils, or preferably with automatic numeric control machines that cut the boards guided through electronic means. These machines allow to make use of informatic means for recording the shape of the different parts and for making necessary changes in them. A single machine can mill, drill and sand the parts besides cutting them out.

2) Obtaining the parts by shaping them in compressing forms:

The application of this method to the production of flat parts is useful because of the simplicity of the substancially flat shape of the forms used. Said forms generally symmetrical to each other move in a way that they compress, between them, the materials of which the parts are thus conformed. With this method, parts can be obtained that are flat in its whole but having a bigger thickness in the centre of the part than in the borders, and these already having a predetermined profile without need for milling them afterwards (see Figure 16). The forms must have substancially flat shapes for assuring the materials being adequately compressed, especially in the part portions near to the outfaces, that is to say near to the forms.
It is particularly interesting the application of this method to the consumption of Medium Density Fiber. The fiber can be compressed in forms having the shape of the different parts, thus avoiding the work of cutting the board and obtaining odds and ends left over.

Claims

A piece of raised up furniture, like table, chair, writing desk, or the like, which supporter is arranged after planes intersecting at vertical or slightly inclined axes defining open volumes, and characterized in that said supporter comprises:
a. a plurality of parts having flat and proportionate shapes, and

b. union means for fixing said flat parts,
having said flat parts an exterior outline curved at least in 50% of its lengh, and being manufactured, as it suits to each kind of part, in the following ways:
* by cutting out flat materials, as boards or the like, preferably with an automatic machine guided through electronic and informatic means, or

* by compressing materials with sliding forms that conform the parts as in a press.
Piece of furniture as claimed in claim 1, characterized in that the parts, although being flat, are shaped like some legs, arms, brackets, stands, or the like, that constitute the supporting structure that holds up the other structures of the piece of furniture.
Piece of furniture as claimed in claim 1, characterized in that the flat parts have proportionate shapes because every section of the part has the minimum possible size keeping the whole a rigidity enough for a normal use.
Piece of furniture as claimed in claim 1, characterized in that wooden Medium Density Fiber ( MDF) is used in its manufacturing.
Piece of furniture as claimed in claim 4, characterized in that said flat parts are manufactured from board having a thickness of between 10 and 70 mm., preferably of:
- 30 mm. for tables and chairs of current use.

- 35 mm. or bigger, for tables and chairs specially rigid and big size furniture, and

- 19 mm. or smaller, for auxiliar furniture and small loads supporting.
Piece of furniture as claimed in claim 1, characterized in that the flat parts have holes interior to its outline that make them light and of strong shapes.
Piece of furniture as claimed in claim 1, characterized in that its supporter is extensible through telescopic guides placed between two of the flat parts.
Piece of furniture as claimed in claim 1, characterized in that it has in its lower portion a stand to which the flat parts are joined.
Piece of furniture as claimed in claim 1, characterized in that the flat parts are joined together in the axes.
Piece of furniture as claimed in claim 9, characterized in that said flat parts being joined together form a nucleus in said axes, from which depart radially some material extensions to shape the supporter of the piece of furniture.
Piece of furniture as claimed in claim 10, characterized in that said nucleus have a smaller size because of being solidly joined to a horizontal structure of the piece of furniture.
Piece of furniture as claimed in claim 9, characterized in that said flat parts are joined together through other parts that facilitate its assembly, like wooden, brass, iron, aluminium or plastic axes.
Piece of furniture as claimed in claim 9, characterized in that said flat parts are joined together through hinges, allowing the supporter to be folding.
Piece of furniture as claimed in claim 9, characterized in that each of said flat parts have an edge portion joined to the sideface of another flat part, thus surrounding the axis.
Piece of furniture as claimed in claim 14, characterized in that it is detachable on using the following union means:
a. four cylindric pieces of central drill, placed said drill in the cylinder axis, and having the cylinder a second drill across its axis, and

b. four screws that join together the four cylindric pieces forming a square that surrounds the vertical axis.
Piece of furniture as claimed in claim 1, characterized in that it is detachable on using any of the following union means:
a. cylindric pieces that have a plurality of female threads, or

b. pieces having a shape adapted to the shape of said flat parts in the place where they are housed, having said pieces of adapted shape a plurality of threads, or

c. pieces exterior to the flat part having a cylindric portion to be fitted in the sidefaces of said flat parts, including means for joining said exterior pieces to the other structures of the piece of furniture.
Piece of furniture as claimed in claim 1, characterized in that it has a detachable padding that comprises:
a. a padded board,

b. means for attaching said padded board to the other parts of the piece of furniture in a detachable way, said means selected from the group of wooden headed screws and rubber headed screws and suitcase fasteners and wedges and screws.
Piece of furniture as claimed in claim 17, characterized in that it has a removable upholstery that includes:
a. a cover that is fixed to said padded board,

b. means for fixing said cover, selected from the group consisting in elastics and zippers and tapes, and placed along the perimeter of the cover in a way that it can be removed for washing it or to be substituted for another one.
Piece of furniture as claimed in claim 18, characterized in that the elastic is sewed directly onto the perimeter of the cover for improving aesthetic results when the padded board is placed against the surface of another board that is a part of the furniture structure.
Piece of furniture as claimed in claim 1, characterized in that a plurality of flat parts are placed:
a. in one of the planes that include the axis, like some flat parts into which a flat part is divided, or

b. in paralell planes that are next to one of the planes that include the axis, like some parts being attached through their flat sidefaces.