Transmission device for curtains

Abstract

A transmission device for curtains includes a bottom board and a mandrel unit is connected on the bottom board. The mandrel unit has first frames and a mandrel which is engaged with the engaging portions of the first frames. The bottom board has multiple guide holes and the first frames are easily connected to the bottom board at the suitable guide holes. A second frame includes a bottom plate, a top plate, a wheel and multiple rollers, wherein the wheel and the rollers are connected between the bottom plate and the top plate. The wheel has a spool and a cord is wrapped between the spool and the mandrel. A coil spring is connected to the spool. Two control cords are wrapped to the mandrel and extends through the head box of the curtain and are connected to the bottom bar of the curtain.

What is claimed is: 
     
         1 . A transmission device for curtains, comprising:
 a bottom board;   a mandrel unit having at least two first frames and a mandrel, each of the at least two first frames having an engaging portion and a passage, the mandrel engaged with the engaging portions of the at least two first frames, and   a second frame having a bottom plate, a top plate, a wheel and multiple rollers, the wheel and the rollers connected between the bottom plate and the top plate, the rollers located on two sides of the wheel, the wheel having a spool and a cord wrapped between the spool and the mandrel, a coil spring connected to the spool.   
     
     
         2 . The transmission device as claimed in  claim 1 , wherein the bottom board has multiple guide holes. 
     
     
         3 . The transmission device as claimed in  claim 2 , wherein each of the at least two first frames has a through hole and a connection member is engaged with the through hole and one of the guide holes in the bottom board.