Lecture 18
Dimitar Stefanov
Wheelchairs and Personal Transportation
Some history:
•Centuries ago – transportation of the disabled on hammocks
slung between poles that were carried by others (upper class
people)
•Wheelbarrow – similar to these for transportation of materials
•During the Renaissance – first wheelchairs – arm chairs with
wheels placed on them (France)
•Wooden wheelchairs – until 1930
•Franklin D. Roosevelt – metal kitchen chairs modified with
wheels
•Civil War: First record of wheelchairs being used in the United
States.
•1907: First patent applied for a folding wheelchair with a steel
frame.
•1936: First single cross-brace steel wheelchair patented by
Everest & Jennings; Everest (mining engineers), Jennings
(engineer)
•Ernest&Jennings – first company for wheelchair manufacture –
few years later
•World War II – steel-framed wheelchairs with 18 inch seat width
•1940s – first powered wheelchairs, standard manual wheelchairs
adapted with automobile starter motors and automobile battery
•Rigid power wheelchair frame – free space under the seat
(battery, controller, respirators, etc.)
•1948: Removable armrests introduced.
•1950's: Lightweight chairs developed for sports use.
•1980's-present: New composite frame materials
developed to further reduce the weight of chairs.
•Personal automobile – modified control of the standard
automobile
•Microcars – enlarged powered wheelchairs, speed about
10 km/h
•The first voice-activated power wheelchair was used in
1984 by a student
• 1995s – omni-directional wheelchairs
Categories of wheelchairs:
1. Manually powered
2. Electrically powered
•200 000 wheelchairs are sold annually within the USA
•20 000 powered wheelchairs
Depot wheelchairs – for institutional use, several people
may use one and the same wheelchair
One-arm-drive wheelchairs – linkage connection of the
rear wheels
Indoor and outdoor wheelchairs
Indoor wheelchairs – short wheelbases, less stable in
lateral direction
•Wheelchairs, powered by the user
•Wheelchairs, powered by attendants
Ultra light wheelchairs
Sports wheelchairs
Categories of wheelchairs (continue)
Stand-up wheelchairs
LifeStand, USA, http://www.lifestandusa.com/home.htm
LEVO, Switzerland, http://www.levo.ch/
•Gas spring activated
•Electric activated
Stair-climbing wheelchairs
Patient transfer systems
Vivax Medical, http://www.vivaxmedicalcorp.com/
Consists of a specially designed electric (hospital type) bed and wheelchair.
The Vivax Mobility System has a transfer conveyor system integrated into the bed frame
which moves the patient from the bed into a specially designed wheelchair and back again. A
built in air support system provides true pressure relief and a low-shear comfortable bed surface.
Patient transfer systems
Beach wheelchairs
http://www.beachwheelchair.com/
Scooters
Shoprider, http://www.dcc-shoprider.com/
Frame design – lightweight tubes
Frame styles:
1. Box-frame wheelchairs (great strength and rigidity)
2. Cantilever frame wheelchairs (the frame can act as suspension; fewer
tubes)
Box-frame wheelchair
Cantilever frame wheelchair
Materials
•Aluminum (6061 aluminum tubing); lightweight, high
corrosion resistance,
•Steel (chromium- molybdenum alloy) – easy to welding,
wall thickness – 0.028 inches, diameter – 0.25-1.25 inches;
•Titanium – lightweight, strong; require special tooling,
high cost;
•Composite materials (carbon fibers) – extremely strong
and tough, lightweight
Two basic styles of powered wheelchairs on the market:
•The traditional style, and
•the platform-model powered chair (powered base and a
chair on it).
Center of gravity (COG)
Located among the midline of the person and the chair
COG – location
Seat width – as narrow as possible; usually 1 inch higher than the user’s
hips
Frame angle
Wheels and caster
Front casters – from 50 to 200 mm in diameter for manual
wheelchairs for daily use.
1. Pneumatic casters
2. Polyurethane casters
Rear wheels – wheels with large diameter
Caster flutter
Rapid vibration on the front wheels
The caster flutter occurs when there is no enough trail.