External venetian blinds have the lowest shading co-efficient of any system. They also reduce the need for artificial lighting as the slats are adjustable and they can be retracted in overcast weather. Tilting the slats also shields against direct glare and provides a diffused and uniform level of daylight. This flexibility of adjustment allows the additional benefit of outward vision whilst maintaining internal privacy.
External venetian blinds have heavy duty aluminium slatting with reinforced edges. The slats have retaining pins that locate in aluminium side guides. The blinds can be manually operated by tracing the operating rod through the building although normally the blinds are electrically operated as part of the building management control system. The blinds should be designed into the building structure with considerable savings in installation costs.
Some slat profiles are designed for a tighter closure so that a dim-out condition can be achieved enabling the room to be used for audio visual presentations.
Types and operation
- Manual - a gearbox is fitted in the headrail with a mono control for both raise/lift and tilt functions. A drive through the building facade connects to a universal joint with a fixed or detachable cranked winding handle.
- Electric - a motor is located within the headrail and operates both the raise/lower and tilt operations.
- Headrail - steel or aluminium to enclose the operating mechanisms.
- Bottom rail - steel or aluminium with nylon end caps with pins that locate in the side guides or cables.
- Slat - aluminium 60mm or 80mm width slats with rolled reinforcing edges.
- Slat guide pins - nylon or cast aluminium pins that are fitted to one alternating end of the slat to retain it in the side guide.
- Ladder braid - polyester braid with cross-ladders through which the slat is threaded (known as anti-fluttering).
- Lift tape - polyester or stainless steel.
- Side guide rail - extruded aluminium with nylon inserts for noise reduction.
- Top box or weather box - aluminium or steel cover to contain the blind when retracted.
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