Sofa with adjustable coupled headrest and backrest

A sofa with an adjustably coupled headrest and backrest, comprising a base and a backrest assembly, wherein the base is movably connected with a side panel and a coupling sheet for backrest configured to be hinged at the side panel, the backrest assembly comprises a connection element of backrest and a connection rod of backrest, wherein a front end of the connection element of backrest is hinged on a rear end of the side panel at an upper position, an upper end of the connection rod of backrest is hinged at a rear end of the connection element of backrest, a lower end of the connection rod of backrest is hinged at the coupling sheet for backrest, wherein the connection element of backrest, the connection rod of backrest, the coupling sheet for backrest and the side panel form a four-bar linkage structure, the base is provided with a drive member configured for driving the side panel to swing, so that a backrest frame is switched to be in a lying position, wherein the connection element of backrest is detachably connected with the backrest frame, the backrest frame is hinged with a connection element for headrest located above the connection element of backrest, and a coupling assembly for headrest configured to force the connection element for headrest to flip relative to a backrest skeleton is provided between the connection rod of backrest and the connection element for headrest,

• wherein the connection element for headrest comprises a first headrest rod hinged at the backrest frame at a lower part of the first headrest rod and a second headrest rod fixedly connected to a lower end of the first headrest rod, wherein the coupling assembly for headrest comprises a first coupling sheet for headrest, a second coupling sheet for headrest, a first headrest linkage, a reversing link and a second headrest linkage, a lower part of the first coupling sheet for headrest is hinged at the connection rod of backrest, a lower part of the second coupling sheet for headrest is at a front side of the second coupling sheet for headrest hinged at the connection element of backrest, the lower part of the second coupling sheet for headrest is at a rear side of the second coupling sheet for headrest hinged at an upper part of the first coupling sheet for headrest, a lower part of the first headrest linkage is hinged at an upper part of the second coupling sheet for headrest, a middle part of the reversing link is hinged at the backrest frame, a front side of the reversing link is hinged at an upper part of the first headrest linkage, a rear side of the reversing link is hinged at a lower part of the second headrest linkage, and an upper part of the second headrest linkage is hinged at a lower part of the second headrest rod.