The Science Behind Scissor Lifts - How Scissor Lifts are Made

Scissor lifts are mobile working platforms that rise. Their elevating mechanism consists of arms that are connected at the middle like scissors, hence the name. Scissor lifts are commonly used at warehouses and construction sites. They are also used in buildings where workers need a safe working platform to carry out maintenance and repairs at heights.

These robust and reliable machines make working at heights much more convenient and safer than using ladders or stepladders. Use of simple and straightforward technology and high grade materials make scissor lifts highly dependable, provided you are using the right weight and height specification for your job.

How Scissor Lifts are Made

The science behind scissor lifts might remind you of your elementary school, as you might have studied these principles in your 5th grade. Here, you can see them practically at work. Scissor lifts work on the principle of hydraulics.

The number of arms in a scissor lift varies depending upon the height of the lift. These are manufactured by cutting square steel pipes of appropriate thickness and length. A hole is cut out in the center of each length of pipe (each scissor-arm) for the central pivot to pass through.

When raising the lift, hydraulic fluid from a sump is pumped into the pressure hoses, which are screwed into a piston-cylinder mechanism. As the cylinder is filled with pressurized hydraulic fluid, the piston moves to raise the scissor arms. As the arms are hinged at their centers and connected to another pair of arms on top, and then another, the movement of the lower-most pair of scissor-arms translates into the movement of all the arms, raising the scissor lift. When lowering, the excess hydraulic pressure is bled out through a bleed hose leading back to the main sump.

The pivots or the joints bear maximum loads and face the stress from the rotation each time the lift is raised or lowered. Therefore, most of the engineering goes into the connections between the scissor arms. There's one connection in the middle, and two connections on the upper and lower end of each arm. Advanced welding techniques including robotic welding are deployed to manufacture the hinged joints at each end of the arms, while the connection at the center is reinforced by welding a small cylinder into the hole that was cut earlier through each arm's center.

Reinforced steel rods are inserted and secured into place using locking pins. When the scissor-arms are ready, primer and rust proof paint is applied to them. As the paint dries up, the other two parts of the scissor lift are getting ready. These are the top platform and the base assembly.

The base assembly contains a set of steerable front wheels. The front wheel assembly is connected to a second hydraulic cylinder, which just controls the left and right movement of the wheels. A hydraulic tray is also stacked into the base assembly on one side, and a battery pack is installed on the other side. Hoses connecting the hydraulic pump to the cylinders are screwed firmly in place.

The top platform is just a steel platform with safety railing. When the three components of the scissor lift are ready, it's time to join them to each other. The scissor-arms are attached to the base and the hydraulic cylinder is attached to the bottom pair of scissors. The steering cylinder is connected to the control panel on the top platform via an electrical interface. The batteries are connected to the hydraulic pump and the controls installed on the platform. Everything is tested and the safety decals are applied before the scissor lift is moved into the warehouse for sale.

Author: Dr Garry McClean is a staff writer at The Workplace Depot - a leading UK supplier of industrial and workplace products