Patent ID: 7677293

Claim:
A control unit for use in a window blind head rail assembly comprising: a sprocket wheel, a sprocket support and wrap spring or springs, a splined bush for engagement with a roller blind tube, a centre-pin, and a plug for releasable engagement with the centre-pin; wherein the plug and centre-pin form a releasably inter-engaging combination whereby insertion of the centre-pin through the control unit and engagement with the plug ensures that a tip of the centre-pin engages an external surface of the splined bush, said plug having a first end defining a cap that is positioned proximate and external to said tip of the centre-pin upon full engagement between said plug and said centre-pin, a second end opposite to said cap, a shaft extending from said first end to said second end, said cap extending radially outwardly from said shaft, and at least one engaging member extending radially outwardly from said shaft, said engaging member located externally of said splined bush.