Evacuation Chair

Overview

An evacuation chair solves a specific failure of building egress: lifts are barred during fire alarms, so anyone who cannot walk down stairs, wheelchair users, post-surgical patients, people injured in the incident itself, needs a way down that one untrained colleague can operate. Carrying a person downstairs in an ordinary chair takes four trained bearers; a track-type evacuation chair lets a single operator take a 150 kg occupant down multiple flights at a controlled walking pace, with the machine, not the operator, holding the load back.

The chairs hang folded on stairwell walls in offices, hospitals, and transport buildings, and the design brief follows from that placement: under 13 kg, deployable in seconds, operable from a pictogram card by someone who has never touched one.

How the descent works

The core idea is the Track Descent System. Two reinforced rubber Track Belt runs, carried on a Track Frame angled to the stair pitch, bridge across the stair nosings, the chair never drops step to step, it slides on a continuous rubber surface contacting two or three nosings at once. Track Roller beds on Ball Bearing races support the belts under load, Belt Tension Axle adjusters keep them taut, and the Track Deploy Linkage swings the track set down and locks it over-center as the operator tilts the chair at the stair head; on many models this happens automatically with the tilt, requiring no separate action.

Belt friction alone would let a heavy occupant accelerate, so descent speed is closed-loop mechanical: the Brake Governor. Belt motion drives the Governor Pinion through a speed-multiplying Helical Gear Pair into a centrifugal brake, above the set speed, Governor Shoe overcome their Coil Spring retractors and expand against the fixed Governor Drum, braking harder the faster the belts turn. The result is a self-regulating descent around 0.5–1 m/s whether the occupant weighs 60 kg or 150 kg, on a gentle or steep flight. Descent energy leaves as heat in the drum. A manual Parking Brake holds the chair dead on the stairs for rest stops or transfer.

Frame, handles, restraints

The Seat Frame is a scissor-folding chassis of anodized aluminum Main Frame Rail and Cross Brace members. Pulling the seat open snaps the Fold Lock catches over-center, squaring the frame rigid; folding reverses in one motion to a 200 mm-thick package. The Seat Assembly sling and flip-down Footrest position the occupant with weight centred over the tracks.

Operator geometry is set by the Operator Handles: the Rear Telescoping Handle telescopes so the operator stands upright two steps above the chair, steering and tilting rather than carrying, while the fold-out Front Handle lets a second person steady the foot end or two-person-lift the chair over a landing obstacle. Handle Position Lock detents fix each position and the Grip Set keeps gloved or sweating hands on the tubes.

The Occupant Restraints matter more than they look: the chair descends tilted back 30–40°, and an unrestrained occupant pitches forward at the first stair. The Lap Belt goes on before any tilt, the Chest Strap holds the torso, the Leg Strap keeps feet on the footrest and out of the belt path, and all three close with glove-operable Buckle Set hardware. A padded Head Support stabilizes weak or unconscious occupants.

Between flights, the chair rolls on its Rolling Gear gear, two rear Wheel Assembly wheels and swiveling Front Caster Wheel units in Caster Fork mounts, pushed like a transport chair along corridors and landings.

Limits and practice

Track chairs are built for straight flights of roughly 30–40° pitch; spiral stairs, escalators, and ascent are outside the envelope, powered stair climbers cover those cases. Descent on the tracks is also one-way down: the governor brakes but does not assist climbing.

Storage is part of the system. The Storage Provision provision hangs the folded chair on a Wall Mount Bracket at the refuge point or stair head, under a high-visibility Dust Cover, with the Instruction Panel pictograms on the chair back for first-time users. UK practice under BS 9999 and BS 8629 ties the chairs to Personal Emergency Evacuation Plans (PEEPs), with named, drilled operators per occupant; US accessibility guidance treats them as a complement to areas of refuge rather than a substitute. Maintenance is light, annual inspection of belts, governor action, buckles, and frame locks, but skipped inspections show up exactly when the chair is needed, so most jurisdictions mandate the schedule.