A wheelchair lift, often called a platform lift, is a mechanical apparatus engineered to safely move individuals using mobility devices between two different vertical elevations. It provides an efficient solution for overcoming architectural barriers like porches, decks, or flights of stairs. Its primary function is to restore accessibility and promote independence in residential and commercial settings where ramps or conventional elevators are impractical. The design centers on a stable platform that travels along a defined path, translating motor power into controlled vertical or inclined motion.
Classifying Wheelchair Lifts by Placement and Form
The form and placement of a wheelchair lift are determined by the architectural environment it serves, leading to three main categories of design. Vertical Platform Lifts (VPLs) are the most common type, operating like a small elevator to achieve a straight vertical elevation change, such as accessing a raised porch or a second floor landing. These self-contained units travel along a mast or tower, requiring minimal structural modification compared to a full elevator installation.
Inclined Platform Lifts (IPLs) are designed to carry a user along the incline of an existing staircase. The platform travels on a rail system mounted directly to the stairs or a nearby wall, making them suitable where installing a vertical shaft is not possible. IPLs are available for both straight and complex, curved stairways with intermediate landings.
A third major type is the Vehicle Lift, engineered to be installed in or on a van, bus, or other transport vehicle. These lifts typically fold out from the vehicle door and operate to raise or lower the passenger from the ground level into the vehicle interior.
The Three Primary Operating Mechanisms
The actual movement of the platform is achieved through one of three primary engineering mechanisms, which convert the motor’s rotational energy into linear lifting force.
Screw Drive System
The Screw Drive System is widely used, particularly in residential VPLs, due to its simplicity and reliability. An electric motor spins a long, threaded rod (an ACME screw), causing a large nut attached to the platform to travel up or down the threads. This direct mechanical connection ensures the platform cannot back-drive or fall, offering inherent safety.
Hydraulic System
The Hydraulic System uses fluid under pressure to generate lifting force, making it common in commercial VPLs designed for heavier loads and faster speeds. An electric pump forces hydraulic fluid into a cylinder, pushing a piston to raise the platform. Descent occurs when a valve releases the fluid back into a reservoir in a controlled manner, allowing for smooth lowering.
Cable/Chain Drive System
The Cable/Chain Drive System operates similarly to a traditional elevator or hoist. The platform is suspended or supported by cables or chains that wrap around a motorized drum or pulley system. This method requires a robust braking system and often an overspeed governor to prevent uncontrolled descent, as the lifting force is transmitted through tension.
Essential Components and Built-In Safety
Regardless of the drive mechanism, all platform lifts incorporate standardized components and layered safety systems. Constant-pressure controls are a fundamental safety feature, requiring the user to continuously hold the operating button for the lift to move. If the button is released, the platform immediately stops, giving the passenger full control.
The platform is equipped with a non-skid surface and often includes a safety pan, or obstruction sensor, located beneath the deck. If the descending platform encounters an object, this sensor instantly cuts power to the motor and stops the lift’s downward travel. Entry and exit are secured by automatic gates or ramps that must be locked in place before the lift will operate, preventing movement while the user is boarding or alighting.
Limit switches are precisely positioned electrical sensors that signal the drive system to automatically cut power and stop the platform exactly at the upper and lower landing points. For situations involving power loss, lifts include an emergency stop button on the platform (a manual override) and a manual lowering mechanism. This mechanism, which might be a hand crank or a release valve for hydraulic fluid, allows the platform to be safely brought down to the lower level.