150E louver on a L 65 mm rack arm

The extruded louvers from the 145-E and up, and the wooden louvers 148-W and up, make use of the L-system. These louvers have larger heights, and are heavier, than those using the S-system, so they require a sturdier foundation.

An assembled L-system rack arm contains at least the following components::

  • rack arm
  • pivot arms
  • slat clips
  • operating strip
  • bearing bracket
  • drive set


These parts are located at the so called (operating) strip side of the rack arm.

The rack arms also carry the operation of a blind, which includes a gearwork and a motor, or a crank. These partys are located at the other side of the rack arm – the motor side.

L-system rack arms are profiles manufactured from 6060 T66 grade aluminium. The heavy duty rack arm, as displayed above, is 65 mm high and incorporates a track to accept the pivots and two nut slots to allow fixings. During pre-assembly, the rack arm is notched to ensure that the pivot are located in the correct position.

The pivot arms are located into the notches of the rack arm, this is a positive fix. Once inserted they cannot be taken out. The slat clips, which hold the louver, are connected to the pivots. Pivots and slat clips, jointly referred to as clips, are made from (PA) polyamide  or (PP) polypropylene. This is done in-house with injection moling.

The operating strip is drilled to the same pitch and accuracy as the notching of the rack arm. If the pitch of the operating strip holes does not exactly match the pitch of the rack arm, then the system will not open and close correctly. The slat clips have extended lugs to which the operating strip is attached. The operating strip therefore attaches all the slat clips together and ensures that they move in a uniform manner.

The bearing bracket is placed at the lower side of the rack arm. The bearing bracket is connected to the operating strip through a drive set.

This drive set consists of a link arm and a claw grip. When this is done, the rotating of the bearing bracket converts into a linear motion of link arm and operating strip which convert into the rotational movement of the slat clips around the pivots allowing them to move from fully open to closed.

Bearing brackets can be positioned anywhere along the rack-arm. Their position is defined by the required closing direction. The sketches below show the motor or gearbox position in relation with the closing direction for internal or external blinds.