The extent of the spans that are possible can be overlooked because of the popular perception of roller blinds being mainly suitable for domestic applications. Widths of up to 6 metres and drops of 4-5 metres are commonly available, whilst even larger sizes are possible.

These sizes require rollers and mechanisms that are otherwise used for shutters and shopblinds. Consideration must be given to the make up of the fabric. Dimensional stability is even more important which will require hems and cross seams and a secure method of attachment to the roller.

Provided suitably robust components and fabric make up is specified, the scope of applications is extensive.

Types and Operation

Standard roller blind

A free hanging blind with a metal or wood roller to which a variety of fabrics including solar screening (light control) and/or decorative fabrics can be used.

Aluminium roller with metal spring

Aluminium roller with an internal metal spring. The blind is usually pulled down by a centre cord and will stop at any point by virtue of a ratchet mechanism. To raise the blind, sharply tug the blind down and allow the fabric to ascend.

Wooden roller with metal spring

As above but with a wooden roller.

Friction roller

A friction mechanism or clutch unit inserted in to a aluminium tube, operated by bead or cord control on an endless loop for precise positioning. Maximum drop determined by weight of cloth (mechanism sometimes referred to as a sidewinder or ball chain roller).

Ballrace roller

As metal spring roller, except action mechanism uses encased ball bearings instead of gravity drop pawls. Aluminium or steel rollers can be fitted with gear handle operation or electric motors.

Cassette blinds

Roller blinds with the roller in a head box sometimes with side and bottom channels. Can be used for housing dim-out blinds, solar screening and insect screening. As a decorative feature or to hide the fabric when it is pulled back.

Dim-out blind

Free hanging Roller blind (as above), with varying degrees of light resistant, dependant on fabric being used. To be effective light resistant features are required to the top, sides and bottom of the window.

Blackout blind

As a Dim-out blind, but with extra light resisting features. It can be very difficult to achieve 100% blackout. See other section for more details.

Roller Mechanism

Wrap spring clutch mechanism

A wrap spring clutch mechanism inserted into an aluminium tube, operated by bead or cord control on an endless loop for precise positioning. Pull one side of chain to raise the blind, the other side of chain to lower the blind.

Maximum drop determined by weight of cloth (mechanism sometimes referred to as a sidewinder or ball chain roller).

Side Chain

Endless Loop Chain operation, pull one side of the loop and the blind will lower, pull the other side of the loop to raise the blind.

Spring Side Chain

As the Endless Loop Chain operation, but a spring is used to make the operation light and easy.

Lock Action Spring Standard Spring Roller Blind Operation. The blind is usually pulled down by a centre cord and will stop at any point by virtue of a ratchet mechanism. To raise the blind, sharply tug the blind down and allow to ascend. Care should be taken not to let the blind fly up to the top.

Decelerator Spring

As the spring roller, but the speed of ascent is controlled by a decelerator (braking) mechanism.

Self Acting Spring

A Spring Roller with no locking mechanism so the spring is always acting to close the blind. This is often used in Rooflight applications where the blind is drawn by pulling and cleating off a cord.

Flange end roller

Spool inserted into steel or aluminium tube. Gravity drop operated by cord or tape and cleat.

Fibre roller

Check action spring or friction mechanism fitted into a roller tube made from compressed and glued wood fibres - produced in standard sizes only. Usually DIY or mail order supply. Not recommended for commercial use.

Sheath End Spring

As the Flange End Roller, but fitted with a spring. To lower the blind the cord is pulled, to raise the blind, the cord is released. This is a traditional form of blind and not commonly used.

Motorisation

A wide variety of motorisation options are available for use with roller blinds.

This varies from the simple requirement to operate a single blind via a direct switch or remote control unit to more complex installations tailored to fit exact client needs.

Electric

A motor is fitted within the roller, so only a tiny part of the motor is seen. The motor contains limit switches that are set to stop the blind at the top and bottom of its travel. Control is by a switch or by a choice from the wide variety of control equipment available. There are two fundamental types of motor, Mains Voltage (240V.AC) or low voltage (24V.DC). Generally low voltage is for the smaller blinds and mains for the larger blinds, but there are exceptions.

Radio Motor

The same as Electric Operation, but the motor is fitted internally with a radio receiver. All control and setting is by the handset. As a general rule, one to any number of blinds can be operated from a single handset and the handset can have one or more control channels. One to any number of blinds can be programmed into each channel in any order or combination required. This can be changed at a later date by a simple programming procedure. Usually available are handsets that look like normal wall switches. These can be fitted anywhere (within range) and no wiring is necessary. Key advantage of Radio motors is the simplicity of wiring.

Components

Roller Material

Aluminium

This is a highly versatile material used in a variety of systems, from the largest to the smallest.

Steel

This is a less common material used in a variety of systems, from the largest to the smallest. The steel should be galvanised or painted to protect against rust.

Wood

This is not so common, and is generally only used as a spring roller on small to medium size windows.

Fibre

Generally for use on small windows on budget applications, DIY or mail order

Tin

Not used any more, but may be found in old/traditional Roller Blinds. Consists of tin plate steel, rolled and soldered to form a tube.

Fabrics

There is a vast array of cloth types, patterns and colours available and sold according to customer requirement and function. Some fabrics are more suitable than others for specific requirements, but this can only be found studying the data provided by the manufacturer.

Key points are:

Is through visibility required? You can generally see from the darker side through to the lighter side. This fine during the day when you want to see out, but at night others can see in. Closed weave fabrics will prevent or limit through vision, open weave fabrics will allow through vision. See openness factor 'OF' below.

How much light reduction do you wish to achieve? Openness factor is looked on as a factor of shading. This is not true. You need to look at the Visible Transmittance 'VT' (see below). It is very important to select a low 'VT' figure when reflection on computer screens is a concern. Is Heat Gain an issue? Limiting heat gain will reduce the heat load on the building. In other words, it will stop the building heating up in the sun. Paying attention to this point will reduce air-conditioning costs and allow for a more pleasant environment. See Solar Reflectance 'SR' below.

Shading Coefficient 'SC' measures the efficiency of a fabric in filtering heat coming from the solar radiation. This figure ranges between 0 and 1. A low figure shows an excellent protection against the incoming heat. Please note that the Sc for an external application is better than the Sc for an internal application.

Visible Transmittance

'VT' measures the percentage of visible light coming through the fabric. A low figure shows a very efficient fabric. The 'VT' is identical whether the blind is placed inside or outside.

Openness Factor

'OF' measures the proportion of holes in a fabric. This parameter is important to figure out the degree of visibility through a fabric. The 'OF' is expressed as a percentage. A low 'OF' shows that the fabric is a very close weave.

Solar Transmittance

'ST' measures the proportion of solar energy transmitted through a fabric. It is expressed as a percentage and for the fabric alone. A low figure indicates a good filtration of solar energy by the fabric.

Solar Reflectance

'SR' measures the proportion of solar energy reflected by the fabric. It is expressed as a percentage and for the fabric alone. A high figure indicates a good reflection of solar energy by the fabric.

Solar Absorption 'SA' measures the proportion of solar energy absorbed by a fabric. It is expressed as a percentage and for the fabric alone. A low figure indicates a low absorption.

Component Options

Acorn

Wood or plastic acorn attached to pull cord.

Bottom lath (or bottom rail)

Wood, aluminium or plastic lath attached to bottom edge of fabric in pocket.

Knot holder plate

Plate used to attach pull cord to bottom lath.

Pocket

Pocket formed in the cloth at the bottom to accept lath or weighting strip.

Hem Bar

Instead of the pocket, a solid bar or rail is attached to finish the bottom of the cloth. There are a variety of shapes, sizes and finishes according to the product and function.

Cross Rib

Cross rib or stiffening batten. Usually in pocket across the width of fabric to prevent bowing.

Scallops

Various shapes to enhance bottom of fabric fitted beneath the lath.

Spindle

Centre core of spring mechanism.

Pins

Protruding slot head or round pin that inserts into fixing bracket.

Fabrics

Also cover or blind cloth.

Roller blinds can be specified in fabrics manufactured from a wide variety can be made in a variety of materials. Woven, knitted or non-woven fabrics may be used as the base cloths and specialist coatings are applied to endow the fabrics with performance features to suit a wide variety of applications. Such features can include finishes such as solar protective coatings, for improved solar and optical performance and glare control, and flame retardant coatings. Totally opaque fabrics are available in a variety of substrates to satisfy circumstances where this feature may be required including dim out and blackout capabilities. Screen or mesh fabrics can be used which apply a defined openness factor to allow some privacy and glare control whilst retaining a degree of view through for the operator during daylight hours

Measurement terms

Pin width

Maximum width including pins that insert into brackets.

Barrel width

Width of Roller excluding pins that insert into brackets. Also 'shoulder width'.

Cloth width

Always less than barrel width to allow movement and eliminate cloth chafing fixing brackets.