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.