Sofa with traversable seat support frame for conversion to a single bed

Sofa with pull-out seat to enable it to be used as a single bed, comprising a rectangular supporting frame (1), provided with supporting feet (12) resting on the ground and with rigid vertical perimeter structures forming the back (3) and arms (4), there being disposed within the frame (1) two pairs of rectilinear guides (13, 13a) parallel to each other and carrying the arms (4) on the transverse sides, between each pair of which are mounted free-running rollers (14, 15, 16) with horizontal axes, capable of supporting and guiding a bar-shaped member (17) which is freely slidable between the said pairs of parallel guides (13, 13a), being integral at their front ends with a longitudinal bar (19) provided with supporting wheels (19a) resting on the floor, enabling two stable positions to be assumed, one of which positions, being further from the back, is capable of enabling the seat to be used as a single bed.