DESC:Field of invention
The present invention relates to a sofa convertible into a bunk bed.

Background of the invention
Various combination sofa bunk beds are known. Most include fairly complex structures and linkages for controlling the movement of the unit that defines either the sofa back or the upper bunk. Also, the support for the upraised upper bunk is relatively complex. Additionally, these combinations often must occupy considerably more floor space when in their bunk bed mode than when in their sofa mode. Further, self-contained storage for objects which might be needed when the bed is opened, as with pillows, is typically not provided. In addition, assembly and disassembly of the sofa bunk bed combinations is rather complex.

One such collapsible bunk bed is described in EP 2 844 110 B1. Disclosed herein is a mechanism for collapsible bunk bed which does not entail a rotation of the upper bed frame, that uses an extremely limited number of levers while maintaining high structural stability, renders the safety mechanism activatable compulsorily by the user in order to be able to use the bunk bed, provides for a safety mechanism that forces the user to assemble at least one longitudinal safety barrier of the upper bed frame in order to be able to use the bunk bed, avoids the need to have a removable ladder and provides for a mechanism that is highly reliable, relatively easy to provide and at competitive costs.

Similarly, US 4,555,821 describes a sofa bunk bed combination which is easily converted between the sofa and the bunk bed modes ,is able to convert the combination to a single bed mode, readily provides support for the upper bunk once the back of the sofa has been raised to define the upper bunk, provides for storage of objects which are accessible in the bunk bed modes and single bed and to hide the storage area in the sofa mode, provides a combination which requires no additional floor space as a bunk bed than as a sofa, facilitates the knockdown assembly and disassembly of the sofa bunk bed, and simplify the construction of the combination.

US 2019/0014910 discloses a system for realizing a sofa-bed which can be converted into a bunk bed which reduces dimensions when the sofa-bed is in the sofa configuration, which is simple to be made by the user and which guarantees that upholsterers and generally those who make the stuffed portion of the piece of furniture have the maximum freedom of expression, thus allowing to reach, at low costs, better aesthetic and design results. Moreover, the system disclosed here comprises a ladder which is automatically extracted when the system is actuated to pass from the sofa configuration to the bunk bed and vice versa it is automatically retracted when the system is actuated in the opposite direction.

The existing sofa bunk beds emphasise mostly on the mechanism of converting the sofa into a bunk bed, without discussing on ergonomics, space optimization and user comfort. in other words, the state-of-the-art bunk beds do not emphasise much on ergonomic, aesthetics, space savings and user friendliness.

It was, therefore, an object of the present invention to provide a sofa convertible into a bunk bed, which has an innovative and ergonomic design, promotes safety, optimized space usage, and user friendliness, without compromising on its strength and durability.

Summary of the invention

Surprisingly, it has been found that the above-identified objects are met by the present invention as described hereinbelow and as reflected in the claims.

Accordingly, in one aspect, the presently claimed invention is directed to a sofa (100) convertible into a bunk bed comprising:
a base bed frame (110) comprising a first side frame (111), a second side frame (112), a plurality of cross members (113) and a plurality of longitudinal members (114),
an upper bed frame (120) configured to be disposed under said base bed frame (110) in a seating position and to be disposed above said base bed frame (110) in a bunk bed position, said upper bed frame (120) comprising a first side frame (121), a second side frame (122), a plurality of cross members (123) and a plurality of longitudinal members (124),
a connector frame (130) comprising upper sides (131, 132) and lower sides (133, 134), and
a rear frame (140) connected to the base bed frame (110),
wherein a lower side (121b) of the first side frame (121) and a lower side (122b) of the second side frame of the upper bed frame (120) are connected to the upper sides (131, 132) of the connector frame (130), on opposite sides, by a first hinge unit (170),
wherein a ladder (150) is connected to a longitudinal member (124) of the upper bed frame (120) by a second hinge unit (180), said ladder (150) configured to be disposed under the upper bed frame (120) in the seating position and to be disposed perpendicularly to the longitudinal member (124) of the upper bed frame (120) in the bunk bed position,
wherein the ladder (150) comprises a plurality of longitudinal members (151) and a plurality of cross members (152), said longitudinal members (151) and cross members (152), independent of each other, at least partially covered with a polyurethane material, and
wherein a first mattress (115) is disposed on the plurality of cross members (113) and the plurality of longitudinal members (114) of the base bed frame (110), and a second mattress (125) is disposed on the plurality of cross members (123) and the plurality of longitudinal members (124) of the upper bed frame (120), said first mattress (115) and second mattress (125), independent of each other, made of a polyurethane foam having a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1.
Brief description of the figures

Fig. 1 is a perspective view of an embodiment of a sofa bunk bed, according to the invention in bunk bed position.

Fig. 2 is a perspective view of the embodiment depicted in Fig. 1.

Fig. 3 is a perspective view of the sofa bunk bed of Fig. 2 in a seating position.

Detailed description of the invention

Before the present compositions and formulations of the invention are described, it is to be understood that this invention is not limited to particular compositions and formulations described, since such compositions and formulation may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

The terms "comprising", "comprises" and "comprised of'' as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of'' as used herein comprise the terms "consisting of'', "consists" and "consists of''.

Furthermore, the terms "first", "second", "third" or "(a)", "(b)", "(c)", "(d)" etc. and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. In case the terms "first", "second", "third" or “(A)”, “(B)” and “(C)” or "(a)", "(b)", "(c)", "(d)", "i", "ii" etc. relate to steps of a method or use or assay there is no time or time interval coherence between the steps, that is, the steps may be carried out simultaneously or there may be time intervals of seconds, minutes, hours, days, weeks, months or even years between such steps, unless otherwise indicated in the application as set forth herein above or below.

In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment but may. Furthermore, the features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

Furthermore, the ranges defined throughout the specification include the end values as well, i.e. a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, the applicant shall be entitled to any equivalents according to applicable law.
An aspect of the present invention is embodiment 1, directed to a sofa (100) convertible into a bunk bed comprising:
a base bed frame (110) comprising a first side frame (111), a second side frame (112), a plurality of cross members (113) and a plurality of longitudinal members (114),
an upper bed frame (120) configured to be disposed under said base bed frame (110) in a seating position and to be disposed above said base bed frame (110) in a bunk bed position, said upper bed frame (120) comprising a first side frame (121), a second side frame (122), a plurality of cross members (123) and a plurality of longitudinal members (124),
a connector frame (130) comprising upper sides (131, 132) and lower sides (133, 134), and
a rear frame (140) connected to the base bed frame (110),
wherein a lower side (121b) of the first side frame (121) and a lower side (122b) of the second side frame of the upper bed frame (120) are connected to the upper sides (131, 132) of the connector frame (130), on opposite sides, by a first hinge unit (170),
wherein a ladder (150) is connected to a longitudinal member (124) of the upper bed frame (120) by a second hinge unit (180), said ladder (150) configured to be disposed under the upper bed frame (120) in the seating position and to be disposed perpendicularly to the longitudinal member (124) of the upper bed frame (120) in the bunk bed position,
wherein the ladder (150) comprises a plurality of longitudinal members (151) and a plurality of cross members (152), said longitudinal members (151) and cross members (152), independent of each other, at least partially covered with a polyurethane material, and
wherein a first mattress (115) is disposed on the plurality of cross members (113) and the plurality of longitudinal members (114) of the base bed frame (110), and a second mattress (125) is disposed on the plurality of cross members (123) and the plurality of longitudinal members (124) of the upper bed frame (120), said first mattress (115) and second mattress (125), independent of each other, made of a polyurethane foam having a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1.

In one embodiment, the first hinge unit (170) and the second hinge unit (180) in the embodiment 1, independent of each other, is made of a plastic material.

In another embodiment, the plastic material is selected from polyoxymethylene, polyurethane and a mixture thereof.

Polyoxymethylene
Polyoxymethylene are acetal polymers and have improved physical properties. The acetal polymer may be further defined as a homopolymer, a copolymer, or a mixture of homopolymers and copolymers. The polyoxymethylene may be further defined as a polyoxymethylene homopolymer (-(-O-CH2-)n-), wherein n is greater than 1. As is known in the art, homopolymers of polyoxymethylene are typically synthesized by polymerizing anhydrous formaldehyde by anionic catalysis and then stabilized by reaction with acetic anhydride. As another example, the polyoxymethylene may be polyoxymethylene copolymer. As is also known in the art, copolymers of polyoxymethylene may be synthesized by converting formaldehyde to trioxane via acid catalysis and then reacting the trioxane with dioxolane or ethylene oxide to form the copolymer using acid catalysts.

In one embodiment, the polyoxymethylene can be reinforced or unreinforced. Suitable reinforcing agents can be selected from, such as but not limited to, glass fiber, aramid fiber, glass beads. The polyoxymethylene modification with additives, such as but not limited to, graphite, molybdenum disulphide (MoS2), polytetrafluoroethylene (PTFE), impact modifiers and heat stabilizers can also be done. Suitable polyoxymethylene has a melt flow index ranging from 2 g/10min to 35 g/10min, determined according to DIN ISO 1133.

Polyurethane
In one embodiment, the plastic material is a polyurethane (PU). In another embodiment, the polyurethane is a thermoplastic polyurethane (TPU). Polyurethanes are obtained as a reaction product of isocyanate, polyol and optionally chain extenders. Polyol and chain extenders together may be classified as isocyanate reactive compounds. Further, additional ingredients such as catalysts and/or additives may also be present during the formation of suitable polyurethanes.

In another embodiment, the TPU has an isocyanate index ranging between 97 to 110. The index is defined as the ratio of the total for number of isocyanate groups used in the reaction to the isocyanate reactive groups. At an index of 100, there is one active hydrogen atom per isocyanate group. At indices exceeding 100, there are more isocyanate groups than isocyanate reactive groups.

In one embodiment, the TPU has a Shore hardness ranging from a Shore A hardness of 25 to a Shore D hardness of 50 determined according to DIN ISO 7619-1.

Isocyanate
Isocyanates can be selected from an aliphatic isocyanate or an aromatic isocyanate. Aromatic isocyanates include those in which two or more of the isocyanato groups are attached directly and/or indirectly to the aromatic ring. Further, it is to be understood here that the isocyanate includes both monomeric and polymeric forms of the aliphatic or aromatic isocyanates. By the term “polymeric”, it is referred to the polymeric grade of the aliphatic or aromatic isocyanate comprising different oligomers and homologues.

Suitable aliphatic isocyanates can be selected from cyclobutane-1,3-diisocyanate, 1,2-, 1,3- and 1,4-cyclohexane diisocyanate, 2,4- and 2,6 methylcyclohexane diisocyanate, 4,4’- and 2,4’-dicyclohexyldiisocyanate, 1,3,5-cyclohexane triisocyanate, isocyanatomethylcyclohexane isocyanate, isocyanatoethylcyclohexane isocyanate, bis(isocyanatomethyl)cyclohexane diisocyanate, 4,4’- and 2,4’-bis(isocyanato-methyl) dicyclohexane, isophorone diisocyanate (IPDI), diisocyanatodicyclo-hexylmethane (H12MDI), tetramethylene 1,4-diisocyanate, pentamethylene 1,5-diisocyanate, hexamethylene 1,6-diisocyanate (HDI), decamethylene diisocyanate, 1,12-dodecane diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, 2,4,4-trimethyl-hexamethylene diisocyanate, and 2-methyl-1,5-pentamethylene diisocyanate.

Suitable aromatic isocyanate is selected from toluene diisocyanate; polymeric toluene diisocyanate, methylene diphenyl diisocyanate; polymeric methylene diphenyl diisocyanate; m-phenylene diisocyanate; 1,5-naphthalene diisocyanate; 4-chloro-1; 3-phenylene diisocyanate; 2,4,6-toluylene triisocyanate, 1,3-diisopropylphenylene-2,4-diisocyanate; 1-methyl-3,5-diethylphenylene-2,4-diisocyanate; 1,3,5-triethylphenylene-2,4-diisocyanate; 1,3,5-triisoproply-phenylene-2,4-diisocyanate; 3,3'-diethyl-bisphenyl-4,4'-diisocyanate; 3,5,3',5'-tetraethyl-diphenylmethane-4,4'-diisocyanate; 3,5,3',5'-tetraisopropyldiphenylmethane-4,4'-diisocyanate; 1-ethyl-4-ethoxy-phenyl-2,5-diisocyanate; 1,3,5-triethyl benzene-2,4,6-triisocyanate; 1-ethyl-3,5-diisopropyl ben-zene-2,4,6-triisocyanate, tolidine diisocyanate, 1,3,5-triisopropyl benzene-2,4,6-triisocyanate and mixtures thereof.

Polyol
Polyols are isocyanate reactive compounds, having a molecular weight above 500 g/mol. Suitable polyols have an average functionality in between 1.9 to 8.0, or in between 1.9 to 6.0 and an OH value in between 10 mg KOH/g to 1000 mg KOH/g, or in between 10 mg KOH/g to 500 mg KOH/g. Standard methods to determine the OH value are well known to the person skilled in the art. For instance, ASTM D4274 can be employed for determining the OH value of the polyols.

In one embodiment, the polyol can be selected from a polyether polyol, polyester polyol and polycarbonate polyol. Mixture of these polyols can also be used.

Suitable polyether polyols are obtainable by known methods, for example by anionic polymerization with alkali metal hydroxides, e.g., sodium hydroxide or potassium hydroxide, or alkali metal alkoxides, e.g., sodium methoxide, sodium ethoxide, potassium ethoxide or potassium isopropoxide, as catalysts and by adding at least one amine-containing starter molecule, or by cationic polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate and so on, or fuller’s earth, as catalysts from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene moiety.

Starter molecules are generally selected such that their average functionality is in between 2.0 to 8.0. Optionally, a mixture of suitable starter molecules is used.

Starter molecules for polyether polyols include amine containing and hydroxyl-containing starter molecules. Suitable amine containing starter molecules include, for example, aliphatic and aromatic diamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, phenylenediamines, toluenediamine, diaminodiphenylmethane and isomers thereof.

Other suitable starter molecules further include alkanolamines, e.g. ethanolamine, N-methylethanolamine and N-ethylethanolamine, dialkanolamines, e.g., diethanolamine, N-methyldiethanolamine and N-ethyldiethanolamine, and trialkanolamines, e.g., triethanolamine, and ammonia.

Hydroxyl-containing starter molecules comprise of sugars, sugar alcohols, for e.g. glucose, mannitol, sucrose, pentaerythritol, sorbitol; polyhydric phenols, resols, e.g., oligomeric condensation products formed from phenol and formaldehyde, trimethylolpropane, glycerol, glycols such as ethylene glycol, propylene glycol and their condensation products such as polyethylene glycols and polypropylene glycols, e.g., diethylene glycol, triethylene glycol, dipropylene glycol, and water or a combination thereof.

Suitable alkylene oxides having 2 to 4 carbon atoms are, for example, ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide and styrene oxide can also be used to obtain the polyether polyol. Alkylene oxides can be used singly, alternatingly in succession or as mixtures. In one embodiment, alkylene oxides are propylene oxide and/or ethylene oxide.

In one embodiment, suitable polyether polyols are derived from tetrahydrofuran. Tetrahydrofuran is a cyclic ether and is converted into a linear polymer called poly(tetramethylene ether)glycol (PTMEG) before obtaining the TPU resin. Commercially available polytetrahydrofuran, under the tradename PolyTHF® from BASF, can also be used.

Suitable polyester polyols are based on the reaction product of carboxylic acids or anhydrides with hydroxy group containing compounds. Suitable carboxylic acids or anhydrides have preferably from 2 to 20 carbon atoms, or from 4 to 18 carbon atoms, for example succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, oleic acid, phthalic anhydride.

Suitable hydroxy group containing compounds comprise of ethanol, ethylene glycol, propyl-ene-1,2-glycol, propylene-1,3-glycol, butyl-ene-1,4-glycol, butylene-2,3-glycol, hexane-1,6-diol, octane-1,8-diol, neopentyl glycol, cyclohexane dimethanol (1,4-bis-hydroxy-methylcyclohexane), 2-methyl-propane-1,3-diol, glycerol, trimethylolpropane, hex-ane-1,2,6-triol, butane -1,2,4-triol, trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polyethylene-propylene glycol, dibutylene glycol and polybutylene glycol.

Polycarbonate polyol is herein also referred to as polycarbonate diol. The polycarbonate diol in a preferred embodiment is linear and has terminal hydroxyl groups. The essential reactants are glycols and carbonates. Glycols are also referred to as alkane diol. Suitable glycols or alkane diols are selected from aliphatic diols containing 4 to 40, and from polyoxyalkylene glycols containing 2 to 20 alkoxy groups per molecule with each alkoxy group containing 2 to 4 carbon atoms.

Other polyols, such as but not limited to, natural oil polyol and graft polyol may also be used in the present invention.

Natural oil polyol (NOP) is also known as biopolyol. In other words, the polyol is not a petroleum-based polyol, i.e., a polyol derived from petroleum products and/or petroleum by-products. In general, there are a few naturally occurring vegetable oils that include unreacted OH functional groups, and castor oil is typically commercially available and is produced directly from a plant source that has sufficient OH functional group content to make castor oil suitable for direct use as a polyol in urethane chemistry. Most, if not all, other NOPs require chemical modification of the oils directly available from plants. The NOP is typically derived from any natural oil, such as from a vegetable or nut oil. Examples of suitable natural oils include castor oil, and NOPs derived from soybean oil, rapeseed oil, coconut oil, peanut oil, canola oil, etc. Employing such natural oils can be useful for reducing environmental footprints.

In one embodiment, the graft polyol is a polymer polyol. In another embodiment, the graft polyol is selected from polyharnstoff (PHD) polyol, polyisocyanate polyaddition (PIPA) and combinations thereof.

Chain extender
Chain extenders and/or crosslinking agents, if present, can modify the mechanical properties of the PU foam, e.g. the hardness. The chain extenders and/or crosslinking agents comprise diols and/or triols, and also amino alcohols with a molecular weight of less than 399 g/mol, or in between 49 g/mol to 399 g/mol, or even in between 60 g/mol to 300 g/mol. Examples of compounds that can be used are aliphatic, cycloaliphatic and/or araliphatic diols having from 2 to 8, or 2 to 6, carbon atoms, for example ethylene glycol, propylene 1,2-glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, o-, m-, p-dihydroxycyclohexane and bis(2-hydroxyethyl)hydroquinone. It is equally possible to use aliphatic and cycloaliphatic triols, for example glycerol, trimethylolpropane and 1,2,4- and 1,3,5-trihydroxycyclohexane.

Catalyst and additives
Suitable urethane-forming catalysts include those described in US 4,390,645 and in WO 2002/079340. Representative catalysts include tertiary amine and phosphine compounds, metal catalysts such as chelates of various metals, acidic metal salts of strong acids; strong bases, alcoholates and phenolates of various metals, salts of organic acids with a variety of metals, organometallic derivatives of tetravalent tin, trivalent and pentavalent As, Sb and Bi and metal carbonyls of iron and cobalt and mixtures thereof.

Suitable of tertiary amines include, such as triethylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine, N,N, N', N'-tetramethylethylenediamine, pentamethyl-diethylenetriamine and higher homologues (as described in, for example, DE-A 2,624,527 and 2,624,528), 1,4-diazabicyclo(2.2.2)octane, N-methyl-N'-dimethyl-aminoethylpiperazine, bis-(dimethylaminoalkyl)piperazines, tris(dimethylaminopropyl)hexahydro-1,3,5-triazin, N,N-dimethylbenzylamine, N,N-dimethylcyclohexylamine, N,N-diethyl-benzylamine, bis-(N,N-diethylaminoethyl) adipate, N,N,N',N'-tetramethyl-1,3-butanediamine, N,N-dimethyl-p-phenylethylamine, 1 ,2-dimethylimidazole, 2-methylimidazole, monocyclic and bicyclic amines together with bis-(dialkylamino)alkyl ethers, such as 2,2-bis-(dimethylaminoethyl)ether. Triazine compounds, such as but not limited to, tris(dimethylaminopropyl)hexahydro-1,3,5-triazin can also be used.

Suitable metal catalysts include metal salts and organometallics selected from the group of tin-, titanium-, zirconium-, hafnium , bismuth-, zinc-, aluminium- and iron compounds, such as tin organic compounds, preferably tin alkyls, such as dimethyltin or diethyltin, or tin organic compounds based on aliphatic carboxylic acids, preferably tin diacetate, tin dilaurate, dibutyl tin diacetate, dibutyl tin dilaurate, bismuth compounds, such as bismuth alkyls or related compounds, or iron compounds, preferably iron-(Il)-acetylacetonate or metal salts of carboxylic acids, such as tin-II-isooctoate, tin dioctoate, titanium acid esters or bismuth-(III)-neodecanoate.

Suitable additives include, but are not limited to, anti-foaming agents, processing additives, plasticizers, chain terminators, surface-active agents, adhesion promoters, flame retardants, anti-oxidants, water scavengers, fumed silicas, dyes, ultraviolet light stabilizers, fillers, acidifiers, thixotropic agents, transition metals, surfactants, cross-linkers, inert diluents, and combinations thereof. Some particularly suitable additives include, but are not limited to, carbodiimides to reduce hydrolysis, hindered phenols and hindered amine light stabilizers to reduce oxidation and yellowing, benzotriazoles to increase UV light stabilization, glass fillers, and salts of sulfonic acid to increase antistatic properties of the TPU composition.

Fillers, especially reinforcing fillers, include the customary, familiar organic and inorganic fillers, reinforcing agents and weighting agents. Specific examples are inorganic fillers such as silicatic minerals, for example sheet-silicates such as antigorite, serpentine, hornblendes, amphibols, chrysotile, talc; metal oxides, such as kaolin, aluminum oxides, aluminum silicate, titanium oxides and iron oxides, metal salts such as chalk, barite and inorganic pigments, such as cadmium sulfide, zinc sulfide and also glass particles. Useful organic fillers include for example carbon black, melamine, expandable graphite, rosin, cyclopentadienyl resins, graft polyols and graft polymers.

In one embodiment, the reinforcing agent is selected from metal fiber, metalized inorganic fiber, metalized synthetic fiber, glass fiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, aramid fiber, graphite fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, inorganic fiber, aramid fiber, kenaf fiber, jute fiber, flax fiber, hemp fiber, cellulosic fiber, sisal fiber and coir fiber.

In an embodiment, the reinforcing agent may be obtained in any shape and size. In another embodiment, the reinforcing agent is subjected to a surface treatment agent. The surface treatment agent is also referred to as sizing. The reinforcing agent when subjected to the surface treatment agent further improve the mechanical properties of the TPU. Typically, sizing provides adhesion between the reinforcing agent and the TPU.

In another embodiment, the surface treatment agent is a coupling agent and is selected from silane coupling agent, titanium coupling agent and aluminium coupling agent.

In one embodiment, the coupling agent comprises silane coupling agent. Suitable silane coupling agent are selected from aminosilane, epoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ?-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane and vinyltrimethoxysilane.

In one embodiment, the polyurethane material covering the ladder (150) in the embodiment 1 is a thermoplastic polyurethane or a polyurethane foam.

The thermoplastic polyurethane is as described herein and having a Shore hardness ranging from a Shore A hardness of 30 to a Shore D hardness of 40 determined according to DIN ISO 7619-1.

Polyurethane foam (PU foam)
In one embodiment, the PU foam has a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1. The PU foam is preferably obtained by reacting an isocyanate component and an isocyanate reactive component. The isocyanate component can be referred as A-side component, while the isocyanate reactive component can be referred as B-side component. The reaction is preferably carried at an index ranging between 40 to 200.

In an embodiment, the isocyanate component comprises an aliphatic isocyanate or an aromatic isocyanate. The aromatic isocyanate and the aliphatic isocyanates have already been described herein.

In another embodiment, the isocyanate reactive component typically comprises of a polyol and other optional ingredients, such as but not limited to, chain extender, catalyst, blowing agent and additives.

Suitable isocyanate reactive components are described hereinbelow.

Polyether polyol
Polyether polyols according to the invention preferably have an average functionality in between 2.0 to 8.0 and preferably a hydroxyl number in between 15 mg KOH/g to 500 mg KOH/g.

In an embodiment, the polyether polyols are obtainable by known methods, for example by anionic polymerization with alkali metal hydroxides, e.g., sodium hydroxide or potassium hydroxide, or alkali metal alkoxides, e.g., sodium methoxide, sodium ethoxide, potassium ethoxide or potassium isopropoxide, as catalysts and by adding at least one amine-containing starter molecule, or by cationic polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate and so on, or fuller’s earth, as catalysts from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene moiety.

Starter molecules are generally selected such that their average functionality is preferably in between 2.0 to 8.0, more preferably in between 3.0 to 8.0 depending on their function and use in the rigid PU foam application. Optionally, a mixture of suitable starter molecules is used.

Starter molecules for polyether polyols include amine containing and hydroxyl-containing starter molecules. Suitable amine containing starter molecules include, for example, ali-phatic and aromatic diamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, phenylenediamines, toluenediamine, diaminodiphenylmethane and isomers thereof.

Other suitable starter molecules further include alkanolamines, e.g. ethanolamine, N-methylethanolamine and N-ethylethanolamine, dialkanolamines, e.g., diethanolamine, N-methyldiethanolamine and N-ethyldiethanolamine, and trialkanolamines, e.g., triethanolamine, and ammonia.

Preferred amine containing starter molecules are selected from the group consisting of ethylenediamine, phenylenediamines, toluenediamine and isomers thereof. Particularly preferred is a vicinal toluenediamine mixture. Vicinal toluenediamine mixtures are by-products of the manufacture of non-vicinal toluenediamines, for e.g. as described in US 3,420,752.

Hydroxyl-containing starter molecules are selected from the group consisting of sugars and sugar alcohols, for e.g. glucose, mannitol, sucrose, pentaerythritol, sorbitol; polyhydric phenols, resols, e.g., oligomeric condensation products formed from phenol and formaldehyde, trimethylolpropane, glycerol, glycols such as ethylene glycol, propylene glycol and their condensation products such as polyethylene glycols and polypropylene glycols, e.g., di-ethylene glycol, triethylene glycol, dipropylene glycol, and water.

Preferred hydroxyl containing starter molecules are sugar and sugar alcohols such as sucrose and sorbitol, glycerol, and mixtures of said sugars and/or sugar alcohols with glycerol, water and/or glycols such as, for example, diethylene glycol and/or dipropylene glycol. More preferred are mixtures of sucrose with one or more than one – preferably one – compound selected from glycerol, diethylene glycol and dipropylene glycol. Most preferred is a mixture of sucrose and glycerol.

Suitable alkylene oxides having 2 to 4 carbon atoms are, for example, ethylene oxide, propylene oxide, tetrahydrofuran, 1,2-butylene oxide, 2,3-butylene oxide and styrene oxide. Alkylene oxides can be used singly, alternatingly in succession or as mixtures. Preferred alkylene oxides are propylene oxide and/or ethylene oxide, while mixtures of ethylene oxide and propylene oxide that comprise more than 50 wt.-% of propylene oxide are more preferred.

The amount of the polyether polyols is preferably in between 1 wt.-% to 99 wt.-%, based on the total weight of the respective component, preferably based on the total weight of the B-side component.

Polyester polyol
The polyester polyols preferably have an average functionality in between 2.0 to 6.0, and preferably a hydroxyl number in between 30 mg KOH/g to 250 mg KOH/g. Polyester polyols according to the present invention are based on the reaction product of carboxylic acids or anhydrides with hydroxy group containing compounds. Suitable carboxylic acids or anhydrides have from 2 to 20 carbon atoms, preferably from 4 to 18 carbon at-oms, for example succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, oleic acid, phthalic anhydride.

Suitable hydroxy containing compounds are selected from the group consisting of ethanol, ethylene glycol, propylene-1,2-glycol, propylene-1,3-glycol, butyl-ene-1,4-glycol, butylene-2,3-glycol, hexane-1,6-diol, octane-1,8-diol, neopentyl glycol, cyclohexane dimethanol (1,4-bis-hydroxy-methylcyclohexane), 2-methyl-propane-1,3-diol, glycerol, trimethylolpropane, hexane-1,2,6-triol, butane -1,2,4-triol, trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, polyeth-ylene glycol, dipropylene glycol, polypropylene glycol, polyethylene-propylene glycol, dibu-tylene glycol and polybutylene glycol.

The amount of the polyester polyols is preferably in between 1 wt.-% to 99 wt.-%, based on the total weight of the B-side component

Polyether-ester polyol
The polyether-ester polyols have preferably a hydroxyl number in between 100 mg KOH/g to 460 mg KOH/g and preferably an average functionality in between 2.3 to 5.0.

Such polyether-ester polyols are obtainable as a reaction product of i) at least one hydroxyl-containing starter molecule; ii) of one or more fatty acids, fatty acid monoesters or mixtures thereof; iii) of one or more alkylene oxides having 2 to 4 carbon atoms.

Preferred hydroxyl-containing starter molecules of component i) are selected from the group consisting of sugars and sugar alcohols (glucose, mannitol, sucrose, pentaerythritol, sorbitol), polyhydric phenols, resols, e.g., oligomeric condensation products formed from phenol and formaldehyde, trimethylolpropane, glycerol, glycols such as ethylene glycol, propylene glycol and their condensation products such as polyethylene glycols and polypropylene glycols, e.g., diethylene glycol, triethylene glycol, dipropylene glycol, and water.

Said fatty acid or fatty acid monoester ii) is generally selected from the group consisting of polyhydroxy fatty acids, ricinoleic acid, hydroxyl-modified oils, hydroxyl-modified fatty acids and fatty acid esters based in myristoleic acid, palmitoleic acid, oleic acid, stearic acid, palmitic acid, vaccenic acid, petroselic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, a- and g-linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid and cervonic acid. The fatty acid methyl esters are the preferred fatty acid monoesters. Preferred fatty acids are stearic acid, palmitic acid, linolenic acid and especially oleic acid, monoesters thereof, preferably methyl esters thereof, and mixtures thereof. Fatty acids are preferably used as purely fatty acids. Very particular preference is given to using fatty acid methyl esters such as, for example, biodiesel or methyl oleate.

Biodiesel is to be understood as meaning fatty acid methyl esters within the meaning of the EN 14214 standard from 2010. Principal constituents of biodiesel, which is generally produced from rapeseed oil, soybean oil or palm oil, are methyl esters of saturated C16 to C18 fatty acids and methyl esters of mono- or polyunsaturated C18 fatty acids such as oleic acid, linoleic acid and linolenic acid.

Suitable alkylene oxides iii) having 2 to 4 carbon atoms are, for example, ethylene oxide, propylene oxide, tetrahydrofuran, 1,2-butylene oxide, 2,3-butylene oxide and/or styrene oxide. Alkylene oxides can be used singly, alternatingly in succession or as mixtures.

Preferred alkylene oxides are propylene oxide and ethylene oxide, while mixtures of ethylene oxide and propylene oxide that comprise more than 50 wt.-% of propylene oxide are particularly preferred.

Chain extender

Suitable chain extenders are already described hereinabove.

Blowing agent
Any of the physical blowing agents known for the production of rigid PU foam can be used in the process. In a preferred embodiment, the blowing agent is selected from the group consisting of hydrocarbon, hydrofluorocarbon, hydrofluoroolefin, hydrochlorofluorocarbon, hydrochlorofluoroolefin, fluorocarbon, dialkyl ether, cycloalkylene ethers and ketones, fluorinated ethers and mixtures thereof.

Examples of suitable hydrochlorofluorocarbons include 1-chloro-1,2-difluoroethane, 1-chloro-2,2-difluoroethane, 1-chloro-1,1-difluoroethane, 1,1-dichloro-1-fluoroethane and monochlorodifluoromethane.

Examples of suitable hydrofluorocarbons include 1,1,1,2-tetrafluoroethane (HFC 134a), 1,1,2,2-tetrafluoroethane, trifluoromethane, heptafluoropropane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2,2-pentafluoropropane, 1,1,1,3-tetrafluoropropane, 1,1,1,3,3-pentafluoropropane (HFC 245fa), 1,1,3,3,3-pentafluoropropane, 1,1,1,3,3-pentafluoro-n-butane (HFC 365mfc), 1,1,1,4,4,4-hexafluoro-n-butane, 1,1,1,2,3,3,3-heptafluoropropane (HFC 227ea) and mixtures of any of the above.

Suitable hydrocarbon blowing agents include lower aliphatic or cyclic, linear or branched hydrocarbons such as alkanes, alkenes and cycloalkanes, preferably having from 4 to 8 carbon atoms. Specific examples include n-butane, iso-butane, 2,3-dimethylbutane, cyclobutane, n-pentane, iso-pentane, technical grade pentane mixtures, cyclopentane, methylcyclopentane, neopentane, n-hexane, iso-hexane, n-heptane, iso-heptane, cyclo-hexane, methylcyclohexane, 1-pentene, 2-methylbutene, 3-methylbutene, 1-hexene and any mixture of the above. Preferred hydrocarbons are n-butane, iso-butane, cyclopentane, n-pentane and isopentane and any mixture thereof, in particular mixtures of n-pentane and isopentane, mixtures of cyclopentane and isobutane, mixtures of cyclopentane and n-butane and mixtures of cyclopentane and iso- or n-pentane.

Generally, water or other carbon dioxide-evolving compounds are used together with the physical blowing agents. Where water is used as chemical co-blowing agent, typical amounts are in the range from 0.2 wt.-% to 5 wt.-%, based on the total weight of the B-side component, preferably based on the total weight of component A).

Hydrofluoroolefins (HFOs), also known as fluorinated alkenes, that are suitable according to the present invention, are propenes, butenes, pentenes and hexenes having 3 to 6 fluo-rine substituents, while other substituents such as chlorine can be present, examples be-ing tetrafluoropropenes, fluorochloropropenes, for example trifluoromonochloropropenes, pentafluoropropenes, fluorochlorobutenes, hexafluorobutenes or mixtures thereof. Particularly preferable HFOs are selected from the group consisting of cis-1,1,1,3-tetrafluoropropene, trans-1,1,1,3-tetrafluoropropene, 1,1,1-trifluoro-2-chloropropene, 1-chloro-3,3,3-trifluoropropene, 1,1,1,2,3-pentafluoropropene, in cis or trans form, 1,1,1,4,4,4-hexafluorobutene, 1-bromopentafluoropropene, 2-bromopentafluoropropene, 3-bromopentafluoropropene, 1,1,2,3,3,4,4-heptafluoro-1-butene, 3,3,4,4,5,5,5-heptafluoro-1-pentene, 1-bromo-2,3,3,3-tetrafluoropropene, 2-bromo-1,3,3,3-tetrafluoropropene, 3-bromo-1,1,3,3-tetrafluoropropene, 2-bromo-3,3,3-trifluoropropene, E-1-bromo-3,3,3-trifluoropropene, 3,3,3-trifluoro-2-(trifluoromethyl)propene, 1-chloro-3,3,3-trifluoropropene, 2-chloro-3,3,3-trifluoropropene,1,1,1-trifluoro-2-butene and mixtures thereof.

Catalyst
Suitable catalyst for PU foams are well known. For instance, the catalysts described hereinabove can also be used for obtaining PU foams.

Additives
Additives, if present, comprise one or more selected from alkylene carbonates, carbon-amides, pyrrolidones, flame retardants, surfactants, dyes, pigments, IR absorbing materials, UV stabilizers, plasticizers, antistats, fungistats, bacterio-stats, hydrolysis control-ling agents, curing agents, antioxidants and cell regulators. These additives can be present in an amount in between 0.1 wt.-% to 30 wt.-%. Further details regarding these additives can be found, for example, in Kunststoffhandbuch, Volume 7, “Polyurethane” Carl-Hanser-Verlag Munich, 1st edition, 1966, 2nd edition, 1983 and 3rd edition, 1993.

In one embodiment, a third mattress (141) is disposed on the rear frame (140).

In an embodiment, the first mattress (115), the second mattress (125) and the third mattress (141), independent of each other, is made of the polyurethane foam having a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1. In one embodiment, the first mattress (115), the second mattress (125) and the third mattress (141) are all made of the PU foams having same densities. In another embodiment, first mattress (115), the second mattress (125) and the third mattress (141) are made of PU foams having different densities.

In another embodiment, a support railing (160) is disposed on the longitudinal member (124) of the upper bed frame (120) in the embodiment 1, said support railing (160) configured to be disposed under the upper bed frame (120) in the seating position and to be disposed parallelly to the longitudinal member (124) of the upper bed frame (120) in the bunk bed position. In another embodiment, the support railing (160) extends upward and has a height H above the second mattress (125) of the upper bed frame (120), said height H ranging between 100 mm to 150 mm, preferably between 120 mm to 140 mm.

In yet another embodiment, the support railing (160) is covered at least partially with the above polyurethane material covering the ladder (150).

In still another embodiment, the lower sides (133, 134) of the connector frame (130) in the embodiment 1 are disposed on an upper side (111a) of the first side frame (111) and an upper side (112a) of the second side frame (112) of the base bed frame (110).

In another embodiment, the first side frame (121) and the second side frame (122) of the upper bed frame (120) in the embodiment 1 are hingedly connected to first edges (131a, 132a) of the upper sides (131, 132) of the connector frame (130).

In a further embodiment, the first side frame (121) and the second side frame (122) of the upper bed frame (120) in the embodiment 1 rest on second edges (131a, 131b) of the upper sides (131, 132) of the connector frame (130) in the bunk-bed position.

In yet another embodiment, a safety unit (190) is disposed on each of the first side frame (121) and the second side frame (122) of the upper bed frame (120) in the embodiment 1, said safety unit (190) locking the upper bed frame (120) to the second edges (131a, 131b) of the upper sides (131, 132) of the connector frame (130) in the bunk-bed position.

In another embodiment, the first side frames (121, 111) and the second side frames (122, 112) of the upper bed frame (120) and the base bed frame (110) in the embodiment 1 are, independent of each other, at least partially covered with the polyurethane material.

In yet another embodiment, the connector frame (130) is at least partially covered with the above polyurethane material.

In another embodiment, at the seating position, the upper bed frame (120) is configured to be disposed under said base bed frame (110). In a bunk bed position, the upper bed frame (120) is disposed above the base bed frame (110). To dispose the upper bed frame (120) in a bunk bed position, the upper bed frame (110) is pulled out and placed above the base bed frame (110). The conversion of the upper bed frame (120) from seating position to the bunk bed position and vice versa, is manually performed. In another embodiment, the conversion is performed by an automated unit. In yet another embodiment, the conversion is performed by means of actuator system. In a further embodiment the actuator system is hydraulic, pneumatic, electric, thermal, magnetic or mechanical. In a further embodiment, the safety unit (190) that locks the upper bed frame (120) to the second edges (131a, 131b) of the upper sides (131, 132) of the connector frame in the bunk-bed position avoids collapse of the upper bed frame (120).

Reference numeral
Sofa 100
Base bed frame 110
- First side frame 111
- Upper side 111a
- Lower side 111b
- Second side frame 112
- Upper side 112a
- Lower side 112b
- Cross members 113
- Longitudinal members 114
- First mattress 115
Upper bed frame 120
- First side frame 121
- Upper side 121a
- Lower side 121b
- Second side frame 122
- Upper side 122a
- Lower side 122b
- Cross members 123
- Longitudinal members 124
- Second mattress 125
Connector frame 130
- Upper sides 131, 132
- First edges 131a, 132a
- Second edges 131b, 132b
- Lower sides 133, 134
Rear frame 140
- Third mattress 141
Ladder 150
- Longitudinal members 151
- Cross members 152
Support railing 160
First hinge unit 170
Second hinge unit 180
Safety unit 190
Height of support railing H

Illustrative embodiments of the present invention are listed below, but do not restrict the present invention. In particular, the present invention also encompasses those embodiments that result from the dependency references and hence combinations specified hereinafter. More particularly, in the case of naming of a range of embodiments hereinafter, for example the expression "The process according to any of embodiments 1 to 4", should be understood such that any combination of the embodiments within this range is explicitly disclosed to the person skilled in the art, meaning that the expression should be regarded as being synonymous to "The process according to any of embodiments 1, 2, 3 and 4":
I. A sofa (100) convertible into a bunk bed comprising:
a base bed frame (110) comprising a first side frame (111), a second side frame (112), a plurality of cross members (113) and a plurality of longitudinal members (114),
an upper bed frame (120) configured to be disposed under said base bed frame (110) in a seating position and to be disposed above said base bed frame (110) in a bunk bed position, said upper bed frame (120) comprising a first side frame (121), a second side frame (122), a plurality of cross members (123) and a plurality of longitudinal members (124),
a connector frame (130) comprising upper sides (131, 132) and lower sides (133, 134), and
a rear frame (140) connected to the base bed frame (110),
wherein a lower side (121b) of the first side frame (121) and a lower side (122b) of the second side frame of the upper bed frame (120) are connected to the upper sides (131, 132) of the connector frame (130), on opposite sides, by a first hinge unit (170),
wherein a ladder (150) is connected to a longitudinal member (124) of the upper bed frame (120) by a second hinge unit (180), said ladder (150) configured to be disposed under the upper bed frame (120) in the seating position and to be disposed perpendicularly to the longitudinal member (124) of the upper bed frame (120) in the bunk bed position,
wherein the ladder (150) comprises a plurality of longitudinal members (151) and a plurality of cross members (152), said longitudinal members (151) and cross members (152), independent of each other, at least partially covered with a polyurethane material, and
wherein a first mattress (115) is disposed on the plurality of cross members (113) and the plurality of longitudinal members (114) of the base bed frame (110), and a second mattress (125) is disposed on the plurality of cross members (123) and the plurality of longitudinal members (124) of the upper bed frame (120), said first mattress (115) and second mattress (125), independent of each other, made of a polyurethane foam having a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1.

II. The sofa according to embodiment I, wherein the first hinge unit (170) and the second hinge unit (180), independent of each other, is made of a plastic material.

III. The sofa according to embodiment II, wherein the plastic material is selected from polyoxymethylene, polyurethane and a mixture thereof.

IV. The sofa according to embodiment III, wherein the plastic material is polyoxymethylene.

V. The sofa according to embodiment III, wherein the plastic material is polyurethane, preferably a thermoplastic polyurethane.

VI. The sofa according to embodiment V, wherein the polyurethane has a Shore hardness ranging from a Shore A hardness of 25 to a Shore D hardness of 50 determined according to DIN ISO 7619-1.

VII. The sofa according to embodiment V or VI, wherein the polyurethane comprises a reinforcing agent.

VIII. The sofa according to one or more of embodiments I to VII, wherein the polyurethane material covering the ladder (150) is a thermoplastic polyurethane or a polyurethane foam.

IX. The sofa according to embodiment VIII, wherein the thermoplastic polyurethane has a Shore hardness ranging from a Shore A hardness of 25 to a Shore D hardness of 50 determined according to DIN ISO 7619-1.

X. The sofa according to embodiment VIII, wherein the polyurethane foam has a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1.

XI. The sofa according to one or more of embodiments I to X, wherein a third mattress (141) is disposed on the rear frame (140).

XII. The sofa according to one or more of embodiments I to XI, wherein the first mattress (115), the second mattress (125) and the third mattress (141), independent of each other, is made of the polyurethane foam having a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1.

XIII. The sofa according to one or more of embodiments I to XII, wherein a support railing (160) is disposed on the longitudinal member (124) of the upper bed frame (120), said support railing (160) configured to be disposed under the upper bed frame (120) in the seating position and to be disposed parallelly to the longitudinal member (124) of the upper bed frame (120) in the bunk bed position.

XIV. The sofa according to embodiment XIII, wherein the support railing (160) extends upward and has a height H above the second mattress (125) of the upper bed frame (120), said height H ranging between 100 mm to 150 mm, preferably between 120 mm to 140 mm.

XV. The sofa according to embodiment XIII or XIV, wherein the support railing (160) is covered at least partially with the polyurethane material covering the ladder (150).

XVI. The sofa according to one or more of embodiments I to XV, wherein the lower sides (133, 134) of the connector frame (130) are disposed on an upper side (111a) of the first side frame (111) and an upper side (112a) of the second side frame (112) of the base bed frame (110).

XVII. The sofa according to one or more of embodiments I to XVI, wherein the first side frame (121) and the second side frame (122) of the upper bed frame (120) are hingedly connected to first edges (131a, 132a) of the upper sides (131, 132) of the connector frame (130).

XVIII. The sofa according to one or more of embodiments I to XVII, wherein the first side frame (121) and the second side frame (122) of the upper bed frame (120) rest on second edges (131a, 131b) of the upper sides (131, 132) of the connector frame (130) in the bunk-bed position.

XIX. The sofa according to embodiment XVIII, wherein a safety unit (190) is disposed on each of the first side frame (121) and the second side frame (122) of the upper bed frame (120), said safety unit (190) locking the upper bed frame (120) to the second edges (131a, 131b) of the upper sides (131, 132) of the connector frame (130) in the bunk-bed position.

XX. The sofa according to one or more of embodiments I to XIX, wherein the first side frames (121, 111) and the second side frames (122, 112) of the upper bed frame (120) and the base bed frame (110) are, independent of each other, at least partially covered with the polyurethane material.

XXI. The sofa according to one or more of embodiments I to XX, wherein the connector frame (130) is at least partially covered with the polyurethane material.
,CLAIMS:1. A sofa (100) convertible into a bunk bed comprising:
a base bed frame (110) comprising a first side frame (111), a second side frame (112), a plurality of cross members (113) and a plurality of longitudinal members (114),
an upper bed frame (120) configured to be disposed under said base bed frame (110) in a seating position and to be disposed above said base bed frame (110) in a bunk bed position, said upper bed frame (120) comprising a first side frame (121), a second side frame (122), a plurality of cross members (123) and a plurality of longitudinal members (124),
a connector frame (130) comprising upper sides (131, 132) and lower sides (133, 134), and
a rear frame (140) connected to the base bed frame (110),
wherein a lower side (121b) of the first side frame (121) and a lower side (122b) of the second side frame of the upper bed frame (120) are connected to the upper sides (131, 132) of the connector frame (130), on opposite sides, by a first hinge unit (170),
wherein a ladder (150) is connected to a longitudinal member (124) of the upper bed frame (120) by a second hinge unit (180), said ladder (150) configured to be disposed under the upper bed frame (120) in the seating position and to be disposed perpendicularly to the longitudinal member (124) of the upper bed frame (120) in the bunk bed position,
wherein the ladder (150) comprises a plurality of longitudinal members (151) and a plurality of cross members (152), said longitudinal members (151) and cross members (152), independent of each other, at least partially covered with a polyurethane material, and
wherein a first mattress (115) is disposed on the plurality of cross members (113) and the plurality of longitudinal members (114) of the base bed frame (110), and a second mattress (125) is disposed on the plurality of cross members (123) and the plurality of longitudinal members (124) of the upper bed frame (120), said first mattress (115) and second mattress (125), independent of each other, made of a polyurethane foam having a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1.

2. The sofa as claimed in claim 1, wherein the first hinge unit (170) and the second hinge unit (180), independent of each other, is made of a plastic material.

3. The sofa as claimed in claim 2, wherein the plastic material is selected from polyoxymethylene, polyurethane and a mixture thereof.

4. The sofa as claimed in claim 3, wherein the plastic material is polyoxymethylene.

5. The sofa as claimed in claim 3, wherein the plastic material is polyurethane, preferably a thermoplastic polyurethane.

6. The sofa as claimed in claim 5, wherein the polyurethane has a Shore hardness ranging from a Shore A hardness of 25 to a Shore D hardness of 50 determined according to DIN ISO 7619-1.

7. The sofa as claimed in any one of claim 5 or 6, wherein the polyurethane comprises a reinforcing agent.

8. The sofa as claimed in any one of claims 1 to 7, wherein the polyurethane material covering the ladder (150) is a thermoplastic polyurethane or a polyurethane foam.

9. The sofa as claimed in claim 8, wherein the thermoplastic polyurethane has a Shore hardness ranging from a Shore A hardness of 25 to a Shore D hardness of 50 determined according to DIN ISO 7619-1.

10. The sofa as claimed in claim 8, wherein the polyurethane foam has a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1.

11. The sofa as claimed in any one of claims 1 to 10, wherein a third mattress (141) is disposed on the rear frame (140).

12. The sofa as claimed in any one of claims 1 to 11, wherein the first mattress (115), the second mattress (125) and the third mattress (141), independent of each other, is made of the polyurethane foam having a density ranging between 30 kg/m3 to 90 kg/m3 determined according to DIN EN ISO 1183-1.

13. The sofa as claimed in any one of claims 1 to 12, wherein a support railing (160) is disposed on the longitudinal member (124) of the upper bed frame (120), said support railing (160) configured to be disposed under the upper bed frame (120) in the seating position and to be disposed parallelly to the longitudinal member (124) of the upper bed frame (120) in the bunk bed position.

14. The sofa as claimed in claim 13, wherein the support railing (160) extends upward and has a height H above the second mattress (125) of the upper bed frame (120), said height H ranging between 100 mm to 150 mm, preferably between 120 mm to 140 mm.

15. The sofa as claimed in any one of claims 13 or 14, wherein the support railing (160) is covered at least partially with the polyurethane material covering the ladder (150).

16. The sofa as claimed in any one of claims 1 to 15, wherein the lower sides (133, 134) of the connector frame (130) are disposed on an upper side (111a) of the first side frame (111) and an upper side (112a) of the second side frame (112) of the base bed frame (110).

17. The sofa as claimed in any one of claims 1 to 16, wherein the first side frame (121) and the second side frame (122) of the upper bed frame (120) are hingedly connected to first edges (131a, 132a) of the upper sides (131, 132) of the connector frame (130).

18. The sofa as claimed in any one of claims 1 to 17, wherein the first side frame (121) and the second side frame (122) of the upper bed frame (120) rest on second edges (131a, 131b) of the upper sides (131, 132) of the connector frame (130) in the bunk-bed position.

19. The sofa as claimed in claim 18, wherein a safety unit (190) is disposed on each of the first side frame (121) and the second side frame (122) of the upper bed frame (120), said safety unit (190) locking the upper bed frame (120) to the second edges (131a, 131b) of the upper sides (131, 132) of the connector frame (130) in the bunk-bed position.

20. The sofa as claimed in any one of claims 1 to 19, wherein the first side frames (121, 111) and the second side frames (122, 112) of the upper bed frame (120) and the base bed frame (110) are, independent of each other, at least partially covered with the polyurethane material.

21. The sofa as claimed in any one of claims 1 to 20, wherein the connector frame (130) is at least partially covered with the polyurethane material.