In contrast to Roman blinds or Austrian blinds, the mechanism of a Venetian blind is hidden behind metal, plastic or aluminum casings, and is therefore difficult to visualize. However, the basic physics are the same as those of other cord-and-pulley blind systems, and, once you know the function of each part of the mechanism, you will understand how a Venetian blind works. That knowledge makes troubleshooting any problems and cleaning it more effectively easier.
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Basic Structure of a Venetian Blind
The basic structure of a Venetian blind is a number of slats made of plastic, wood or aluminum, which are drawn up or let down by means of a pulley system housed in a top casing which is attached to the top of the window frame. The slats are movable so that they can be opened outwards or inwards or left closed completely. A brake, or cord lock mechanism, hidden in the top casing, allows you to pull the blinds up or let them down part of the way or to keep them held in a stack at the top of the blind frame. The lower edge of the blind acts as the weight and is attached to the whole unit by two pulling cords.
Slat Tilt Mechanism
Each slat is perforated with a hole 4 to 6 inches from each end through which the lifting thread passes. The two outer threads, and the horizontal linking thread or clip between each slat, form the ladder, which is linked to the tilting wand which you turn clockwise or counterclockwise to angle the slats.
Cord Lock Mechanism
Within the casing is the brake mechanism, which, when you pull the cord across the front of the blind, holds the cords firmly to keep the slats at whichever height you raise them. To release the brake, hold the looped cord across the blind and pull gently so that the brake disengages. The cords then run freely through the top casing and lower the blind or raise it, depending on which position you want the blinds to be.
Keeping the looped cord out of reach of small children and pets is crucial as they can get caught up in it. Either screw a cleat high up on the window frame and wind the cord round that, or cut the loop so that you have two ends. You won't lose the ends as they are long enough to hang without being drawn up into the casing.