Staircase combination of the gang sockets

A staircase combination of the gang sockets comprising:

• more than two identical tubular sockets integrally formed and each having an upper rim, a lower rim, a lateral opening and a pair of retaining grooves in opposing inner peripheries for disposing a common contact plate therebetween with a first and a last socket each having a single contact plate disposed into an opposing retaining groove facing said common contact plate and connected to an electric wire which extends out of said first and last socket via the lower rim thereof, said socket being connected by the way that the lower rim of the first socket partially connected with the upper rim of a second socket which in turn has a lower rim partially connected with the upper rim of a third socket and so on until the upper rim of the last socket partially connected to the lower rim of an adjacent socket thereabove;
• more than two covers closing the openings of said sockets and each having an upper end and a lower end, said covers being integrally formed and connected each other by the way that the lower end of a first cover partially connected to the upper end of a second cover which has the lower end partially connected to the upper end of a third cover and so on until a last cover being appeared, said covers being finally connected to said sockets respectively by means of high frequency waves;
• more than two lamps respectively inserted into the upper rims of said sockets and each having a base, a bulb in top of the base and a pair of lead-in wires attached to opposing outer peripheries of the base and engaged with said common contact plates wherein a first and a last lamp having their lead-in wires respectively engaged with the common contact plate and a single contact plate positioned opposite to said common contact plate.
• whereby a series electric circuit is established within said sockets.