Patent ID: 8794296

Claim:
A window blind, comprising: a retractable shading unit; a headrail connected with an upper end of the shading unit; a bottom rail connected with a lower end of the shading unit; at least one connecting cord extended through the shading unit and having a first end secured on the headrail and a second end secured on the bottom rail; wherein the connecting cord has a first elastic section and a second section, wherein: in the first elastic section, the connecting cord has a length that is changed elastically to correspond to an expansion length of the shading unit, and in the second section, the connecting cord has a length that is substantially unchanged during operation of the shading unit; a plurality of limit members mounted in the bottom rail; and a control unit mounted on the bottom rail; wherein the headrail has a side provided with a first opening and has an interior provided with a first track; the bottom rail has a side provided with a second opening and has an interior provided with a second track; the shading unit includes a plurality of shading members located between the headrail and the bottom rail; each of the shading members of the shading unit has a surface provided with a plurality of through holes; the connecting cord is in turn extended through the headrail, the through holes of each of the shading members, the bottom rail and the control unit, and is wound around between the limit members; the second end of the connecting cord is provided with an elastic section; the elastic section of the connecting cord has a length that is changed elastically to correspond to an expansion length of the shading unit, wherein the control unit includes: a housing secured in the bottom rail; a push button movably mounted on the housing; and an elastic member mounted in the housing and biased between the housing and the push button; the housing of the control unit has a surface provided with a first passage to allow passage of the connecting cord; the push button of the control unit has a first end received in the housing and a second end protruding outward from the housing; the push button of the control unit has a surface provided with a second passage to allow passage of the connecting cord; the second passage of the push button is connected to the first passage of the housing; the elastic member of the control unit is biased between the housing and the first end of the push button to push the push button outward relative to the housing; the connecting cord is in turn extended through the first passage of the housing and the second passage of the push button; the connecting cord is clamped between the housing and the push button, and the connecting cord is released when the push button is pressed, wherein only the second section of the connecting cord passes through the control unit during operation of the shading unit.