Mattress arrangement, such as a bed, having adjustable firmness

1. A mattress arrangement, such as a bed arrangement, comprising:

an upper mattress;

a lower mattress being arranged beneath said upper mattress;

a support layer arranged between the upper mattress and the lower mattress, to partly support the upper mattress, said support layer being arranged only partly to support the upper mattress, such that a greater part of a lower surface of the upper mattress remains unsupported by the support layer, said greater part of the lower surface of the upper mattress instead being supported directly by the lower mattress;

wherein the lower mattress has a variable extension in a length direction of the lower mattress and/or a width direction of the lower mattress, such that at least one side of the lower mattress is an at least one moveable side that is moveable in the length direction of the lower mattress and/or the width direction of the lower mattress in relation to an opposite side of the lower mattress, such that the lower mattress is expandable into an expanded state, having a lower firmness, and compressible into a contracted state, having a higher firmness; and

wherein said support layer is arranged overlying said at least one moveable side of the lower mattress to form at least one compartment beneath the upper mattress, said at least one compartment being at least partly empty when the lower mattress is in the contracted state and at least partly filled when the lower mattress is in the expanded state.

2. The mattress arrangement of claim 1 , wherein the lower mattress has the variable extension in at least the length direction of the lower mattress.

3. The mattress arrangement of claim 1 , wherein at least a side arranged at a foot-end of the lower mattress is moveable in relation to a side arranged at a head end of the lower mattress.

4. The mattress arrangement of claim 3 , wherein the side arranged at the head end of the lower mattress is fixed.

5. The mattress arrangement of claim 1 , wherein the lower mattress in its expanded state has outer dimensions corresponding to the outer dimensions of the upper mattress.

6. The mattress arrangement of claim 1 , wherein the lower mattress may further assume at least one, and preferably a plurality, of intermediate states, between said expanded state and said contracted state.

7. The mattress arrangement of claim 1 , wherein the lower mattress is a pocket spring mattress, comprising a plurality of coil springs arranged in pockets.

8. The mattress arrangement of claim 7 , wherein the pocket spring mattress comprises a plurality of parallel strings interconnected side by side, each string comprising a plurality of continuous casings and each casing comprising a coil spring, wherein expansion of the mattress into the expanded state occurs in a least one of a direction being parallel to the plurality of parallel strings and a direction being perpendicular to the plurality of parallel strings.

9. The mattress arrangement of claim 8 , further comprising a pulling or pushing arrangement connected to said at least one side of the lower mattress, to provide a pulling or pushing force to bring the lower mattress to the expanded state.

10. The mattress arrangement of claim 1 , wherein the lower mattress comprises at least one elastic element extending between said at least one moveable side of the lower mattress and said opposite side of the lower mattress, said at least one elastic element being arranged to provide a contraction force to bring the lower mattress to the contracted state.

11. The mattress arrangement of claim 1 , further comprising a frame arranged to at least partly accommodate the lower mattress, wherein said support layer is connected to said frame.