The present invention relates to a system for bunk beds, and in particular a system which allows to convert a bunk bed into a sofa. The present invention relates also to a sofa-bed comprising such system.

At the state of the art there are known many embodiments of bunk beds which can be converted into sofas. A first example is described in the Patent Application EP2110054, in which a system is described to convert a bunk bed into a sofa, characterized in that the frame supporting the upper bed rotates by 180° while passing from the position of usage as bed to the position of usage as sofa. This system is however disadvantageous in that it has to be comprised of separated mattress and sofa-seat, constrained on the two sides of said frame, and in that it is needed to bind them to the frame to prevent them from falling, thus making complex the needed steps to make the bed to go to sleep. Other examples of similar systems are described also in US 4592101, WO 8707487, GB 812928. Another example is shown in WO2013/131946, in which a system is described for a sofa which can be converted into a bunk bed, which uses a four-bar linkage to move the upper bed while keeping it always in horizontal position during its movement. Anyway, the described system is not so robust, since it is provided with only one point of anchorage of the four-bar linkage to the upper frame, and it does not allow the ladder, which makes it easy to access to the upper bed, to be integral part of the structure. Therefore the ladder has to be removed and kept separately.

Aim of the present invention is to provide a system for realizing a sofa-bed which can be converted into a bunk bed which is alternative and better than those known at the state of the art. In particular, aim of the present invention is to provide a system for realizing sofa-beds which can be converted into bunk beds 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 according to the present invention comprises a ladder to makes easier to reach the upper bed, which is automatically extracted when the system is actuated to pass from the sofa configuration to the bunk bed one, and vice versa it is automatically retracted when the system is actuated in the opposite direction.

These and other advantages will be clear from the detailed description of the invention, which refers to the appended figures 1 to 9.

In figure 1 it is shown an axonometric view of a preferred embodiment of a sofa-bed comprising the system according to the present invention in an intermediate position between the completely closed one, shown in figure 2, and the completely opened one, shown in figure 3. In figures 4, 5 and 6 there are shown side views of the system, in bunk bed configuration, sofa-bed configuration and intermediate configuration, respectively. In figures 6 to 9 there are shown some views of the safety stop system: in automatic closing starting position (figures 6 and 7) and in release position (figures 8 and 9) . As it is clear form the analysis of figure 1, the system according to the present invention comprises a base frame (11) provided with feet (111) . The base frame (11) is the stationary part of the system (since it stands on the floor in each configuration of usage the system can be brought into) , has a substantially rectangular shape in plan view, and such dimensions that it houses the other elements of the system, described in the following.

The system comprises also an upper frame (21), which has rectangular shape and such dimensions as well that it houses a base (not shown in figures, typically a slatted bed base or box-spring base or of other kind among those known at the state of the art) and it supports a mattress (211) therein. Conveniently, the upper frame (21) is also provided with safety edges on one of the two long sides (213) and on both the short sides (212) . Another tilting edge is provided on the front long side and can be turned over under the base of the upper bed when not needed. Besides exerting their safety function when the system is in bed configuration, the fixed edges (212, 213) can be used as structures for armrests and back rests when the system is in sofa-bed configuration.

The constraint of the upper frame (21) to the base frame (11) occurs by means of a kinematics with double four-bar linkage, in the following described in detail, which allows to move said upper frame (21) from a first position (shown in figure 2) in which the same is lowered and the system is in sofa configuration, to a second position (shown in figure 3) in which the upper frame is lifted and the system is in bunk bed configuration (in the following it is described the position taken by the frame (25) supporting the second mattress (251) in both the configurations) .

The movement of the upper frame (21) is such that said second position is substantially on the vertical of said first position, and during the movement from said first to said second position the upper frame is kept constantly in horizontal position (in other words it does not rotate but moves in an always parallel position to the starting position) . The movement of said upper frame consists almost exclusively in a vertical translation . The kinematics which allows this movement comprises a mechanism of the following kind on each short side of the sofa. To the base frame (11) a first four-bar linkage is constrained comprising a bar (14) parallel to said base frame (11) and two bars (12, 13) constrained so that they form the other sides of the four-bar linkage. It is to be assumed that the four-bar linkage has two always horizontal sides (11, 14) and two sides (12, 13) which can rotate and take also the vertical position and which, for simplicity, are referred to as "vertical sides", even if it is clear that the vertical position is only one of the positions which said sides (12, 13) can take. It is also to be precised that, unless otherwise specified, for length of a bar of the mechanism it is intended the length measured between the centres of rotation of the two hinges arranged at the ends of the bar.

Referring to the horizontal bar (14) of the first four-bar linkage, the same can be constrained to the vertical bars of the second four-bar linkage rather than to those of the first one, thus carrying out the same function.

Another aspect to be precised concerns the embodiment of the bars of the four-bar linkages, shown in the appended drawings: preferably, but not in limiting way, the vertical bars (12, 13) of the first four-bar linkage comprise each a couple of profiles with rectangular sections, between which the bars of the second four-bar linkage are hinged. This does not rule out the possibility to realize the same kinematics in a different way, for example by using two profiles for the bars of the second four-bar linkage and only one profile for the bars of the first four-bar linkage, or only one profile for them both. Obviously also the shape of the bars can be varied, by using for example a circular section .

To provide a four-bar linkage the distance to which the vertical sides (12, 13) are hinged at the base frame (11) is clearly equal to the length of the bar (14) . The first of the two vertical sides (13) is substantially hinged at the front angle of the base frame (11) . So, the movement of this first four-bar linkage (11, 12, 13, 14) allows to lift and lower the bar (14) while keeping it in horizontal position. Obviously in its movement the bar (14) is also subjected to a horizontal translation, and in particular it moves to the front side when lifted. At equal distance from the base frame (11), at the two vertical hinges (12, 13) of the first four-bar linkage other two bars (22, 23) are hinged which support the upper frame (21) . Also the constraint of said bars (22, 23) to the upper frame occurs by means of hinge constraints. The constraints of these further bars (22, 23) and of the upper frame (21) are such that they make up a second four-bar linkage: thus, the upper frame can only move while remaining horizontal.

According to a preferred embodiment, the first (23) of the bars of the second four-bar linkage is substantially constrained at the angle of the upper frame (21), and the length of the vertical bars of the first and second four-bar linkage, is equal. In this way, the position of the upper frame (21), in plan view, coincides substantially with the one of the base frame (11), both when the frame is lowered in sofa configuration (figure 2) and when it is lifted in bunk bed configuration (figure 3) .

It is also to be highlighted that, as it is clear for example from the view of figure 5, the fact that the constraint of the four-bar linkages occurs at the front angle of the base frame allows to maximize the space at disposal in horizontal direction to house the bars of the four-bar linkages when the mechanism is closed in sofa configuration .

The last element implementing the kinematics is a bar (24) which constrains the movement of the first four-bar linkage (11, 13, 24, 14) to the one of the second four-bar linkage (21, 22, 23) . In fact, in a preferred embodiment, this bar is hinged to the base frame (11) and to one of the vertical bars of the second four-bar linkage (22), and is configured so that it determines the configuration of the second four-bar linkage once the position of the first four-bar linkage is defined. In particular this correspondence between the positions of the two four-bar linkages is such that the bars of the second four-bar linkage (22, 23) are in vertical position when the bars (12, 13) of the first four- bar linkage are in vertical position as well, as shown in figure 3.

Conveniently, to the vertical bars of the first four-bar linkage (12, 13) a third frame (25) is also constrained which is configured to support a second mattress (251) . Said third frame (25) is constrained in horizontal position and moves integrally to the first four-bar linkage movement, moving forward towards the front part of the sofa- bed when it is extracted, thus taking the position shown in figure 4.

The fact that the lower bed takes this position has at least two advantages: firstly it allows to reduce the sensation of constriction of the person who lies on the lower bed, since the upper bed is not perfectly overlapped to the first one, and secondly it allows to position the ladder (31) inclined to the vertical, as described in the following, thus making it easier to access to the upper bed.

In fact the system for sofa-bed can comprise a ladder constrained to the upper frame (21) and to the frame of the lower bed (25) , divided in two parts. The lower part (31) of the ladder is integral to the frame of the lower bed (25) and oriented in vertical position; its vertical dimension is approximately equal to the dimension of the mattress (251) and however such that, when the system is closed in sofa configuration, it does not project with respect to the limit stop bar (113) of the lower frame (11), described in the following. The upper part (31) of the ladder is instead hinged to the lower part of the same ladder and slidingly constrained to the upper frame (21) . In this way, when the upper frame and the lower one are moved closer (i.e. when the system passes from the bunk bed configuration to the sofa configuration) the upper end of the upper part of the ladder (31) slides with respect to the upper frame and tilts up to take a horizontal position and to remain hidden between the two beds when the system is in sofa configuration. Similarly, when the system passes from the sofa configuration to the bunk bed one, the upper part of the ladder (31) moves without any manual intervention needed, up to take the position shown in figure 4.

Preferably, the system comprises also a safety edge constrained by means of hinges to said ladder and configured so that it is interposed between said upper frame (21) and said third frame (25) when the system is in sofa configuration. In fact the safety edge is integral to the ladder in the movement the same carries out when the system passes from a configuration to the other one, anyway when the system is in bunk bed configuration, the safety edge can be rotated up to take the vertical position shown in figure 3. From the analysis of figure 4, it is also clear the provision of the limit stop bar (113), integrally constrained to the base frame (11) and configured so that it acts as stop for the upper frame (21) and determines the position taken by this one when the system is in sofa configuration.

The system for bunk beds according to the present invention comprises also a safety locking system, suitably developed to avoid accidental closing, which could be extremely dangerous for the people lying in the bunk bed.

As it is shown in figure 1, on one of the bars (23) of the second four-bar linkage (21, 22, 23) an automatic locking system is constrained whose functioning is shown in figures 6 to 9. As it is shown in figure 6, the locking system (4) comprises an outer body (42) configured to be integrally mounted to said bar (23) . Preferably said outer body (42) can be realized in two parts of such shape that they allow the housing of the bar (23) therein, when mounted the one on the other one. From the lower part of said lock a couple of teeth (43) project which have an oblique stop surface, slidingly constrained inside said lock between a first position in which they project with respect to the end of the outer body (42) and a second position in which they are completely contained inside the same. The system comprises further a cap

(41) , of such shape that it covers the outer body (42) and constrained by means of pins (46) to each sliding teeth (43) . Said pins (46) slide in respective slots (47) provided on the outer body, thus allowing the cap (41) to vertically translate integrally to said sliding teeth (43) .

A helical spring (44) mounted outside a suitable vertical pin (45) is interposed between the outer body (42) and the sliding tooth (43) so that it pushes outwards said sliding tooth (43), and as a consequence, pulls downwards the cap (41) by means of the pins (46) . Therefore the first stable configuration of the locking system is the one shown in figures 6 and 7. In this position the teeth (43) project with respect to the outer body

(42) . As shown in figure 3, when the locking system (4) is mounted on a vertical bar (23) of the second four-bar linkage and the convertible sofa-bed is in bunk bed configuration, the teeth (43) engage in the upper openings of the two profiles of the respective vertical bar (13) of the first four-bar linkage (obviously in case only one profile is used for the first four-bar linkage the automatic locking system comprises only one tooth) . In this configuration the respective rotation of the bars of the two four-bar linkages is prevented, and since it is provided a bar (24) which constrains the position of the second four-bar linkage to the position taken by the first one, the system as a whole cannot move from the vertical configuration, shown in figure 3. The provision of the spring (44) inside the locking system (4) guarantees that the teeth (43) cannot move from their position, and this prevents the upper bed from being lowered as a consequence of unintentional movements. The only way to close again the sofa-bed is to lift intentionally the cap (41) of the locking system (4) until it takes the position shown in figures 8 and 9, where the teeth are completely contained inside the outer body (42) . In this position the spring (44) is compressed, and pushes the teeth outwards, but the front side (411) of the cap (41) blocks the position of the teeth by engaging in the outer body (42) . When both the locking systems (4) arranged at the two ends of the convertible sofa- bed are in this position, the respective rotation of the bars of the two four-bar linkages is not blocked, and so it is possible to start to close the system in sofa-bed configuration.

Conveniently, at a bar of the first four-bar linkage an abutting element (131) is provided whose position is such that, when the sofa-bed is closed, the cap (41) of the automatic locking system (4) abuts the abutting element (131) which pushes it towards the bar (23) on which it is mounted so that it takes the stable position with projecting teeth (43), also due to the thrust of the spring (44) . When the system is brought again in its configuration of bunk bed, the teeth (43) are yet in their locking configuration. The fact that the teeth (43) have an oblique stopping surface makes it possible that the respective profiles (13) of the first four-bar linkage, by moving closer, lift them firstly and after the spring (44) pushes them outwards to engage in the suitable opening of said profiles (13) . It is not needed any manual action for inserting the locking system which is fitted out and actuated automatically.