Learn about the clever scissor lift mechanism that allows these workhorse machines to safely raise workers to height.
Scissor lifts are mobile elevating work platforms (MEWPs) capable of lifting workers and their tools to heights. They are compact in design, simple to operate and easy to move. So how does a scissor lift work, and what are the different types? Read on to learn more about these popular machines.
How scissors lifts work: The scissor lift mechanism
Scissor lifts rely on a pantograph, or parallelogram, design. Steel support beams, sometimes called legs, are arranged in X patterns, with hinge pins at each intersection. When cylinders attached to a set of beams are filled with hydraulic fluid or compressed air, they exert upward pressure on the outer edge of the higher beam. This forces the X patterns to elongate, lifting the attached platform. When the pressure in the cylinders is released, the platform descends.
Scissor lift components
Here’s a quick look at the main parts of a scissor lift.
The platform, also known as the lift table, holds workers and their tools and serves as the workspace. To help prevent falls, most scissor lift platforms include guardrails.
The base frame supports the rest of the scissor lift. Made of rigid metal, it has tracks to guide rollers at the bottom of the scissor legs, which allow the bottom legs to open and close. Together, the base and rollers help ensure a steady ascent and decent.
These crisscrossed steel beams connect the platform to the base. The longer the legs or the greater the number of legs, the higher the platform can rise.
Scissor lifts have anywhere from one to four cylinders attached to one or more sets of legs. Depending on the type of scissor lift, the cylinders can be filled with hydraulic fluid or compressed air. When the cylinder is filled, it pushes outward, putting upward pressure on a leg and raising the platform.
The down valve, which is connected to the power supply, opens when the operator uses the controls to lower the platform. The opening of the valve allows the hydraulic fluid or compressed air to leave the cylinder, which lowers the platform.
Flow control valve
The flow control valve controls how fast the hydraulic fluid or compressed air leaves the cylinder and how fast it enters. This regulates the speed of the platform’s descent and ascent.
The control panel features an interface that allows the operator to turn on the lift, set the speed, and lift and lower the platform. These panels typically include an emergency stop button to be used in the event of a valve malfunction.
Types of scissor lifts
Different scissor lifts have different power sources, lift capacities and speeds. Some are better suited for indoor or outdoor environments, or for light or heavy duty.
Electric scissor lift
Electric scissor lifts, which are powered by batteries, are more compact than other lifts, so they’re more likely to fit through doorways and other access points and they’re easier to store. Silent, emissions-free operation makes these lifts particularly suitable for indoor use.
Hydraulic scissor lift
These lightweight lifts can be used indoors or outdoors and are commonly found on construction sites and in warehouses. They offer less speed and horsepower than diesel scissor lifts.
How do hydraulic scissor lifts work? They're typically powered by an electric motor and use hydraulic liquid in the cylinders.
Pneumatic scissor lift
A pneumatic scissor lift uses atmospheric air to pressurize the cylinder of the lifting mechanism. Because these lifts emit no fumes, they’re a good fit for indoor spaces and spaces with poor ventilation.
Diesel scissor lift
Diesel lifts can lift more weight than other scissor lifts and travel at greater speeds. In addition, they offer larger work platforms. The tradeoff: noise and emissions. They’re typically used outdoors.
Rough terrain scissor lifts
Rough terrain scissor lifts are powered by diesel, gas or liquid petroleum engines. With heavy-duty tires and features such as four-wheel drive and positive traction control, they are designed to handle difficult and uneven terrain. Some have outriggers for increased stability.
Whether you’re working indoors or outdoors, on a small or large project, the right scissor lift can help you get the job done safely.