How Does a Scissor Lift Work

How Does a Scissor Lift Work

Meta Description: Learn how a scissor lift works: explore its mechanism, hydraulic or electric systems, safety features, and maintenance requirements.

Scissor lifts are essential equipment used in various industries for lifting personnel and equipment. This article discusses the key components and operation of scissor lifts.

It explores the platform, scissor mechanism, hydraulic or electric systems, and operating controls. Safety features and maintenance requirements are also covered.

Key Takeaways

• Scissor lifts have safety features like guardrails, toeboards, and emergency stop buttons to protect operators.
• The scissor mechanism comprising folding scissor arms and legs enables vertical lifting movement of the platform.
• Hydraulic, electric, or pneumatic systems power the lifting unit through hydraulic cylinders, electric motors, or pneumatic pumps.
• Routine maintenance, like fluid checks, lubrication, and inspections, ensures safe operation.
• Overload sensors and control systems prevent accidents from overloading or improper operation.
• Proper training is required before operating scissor lift controls to raise or lower the work platform as needed.

What is a Scissor Lift?

A scissor lift is a platform that uses a scissor mechanism comprising multiple connected scissor blades or legs arranged in an X-pattern to provide vertical movement. When pressure is applied to the scissor legs through hydraulic cylinders, electric motors, pneumatic pumps, or other means, the scissor arms fold inwards and extend outwards, lifting the platform vertically.

Scissor lifts are available in different types, such as hydraulic, electric, rough terrain, etc., to suit various applications.

How the Scissor Mechanism Works

The scissor mechanism is the critical component that enables vertical movement of scissor lifts. It comprises multiple connected scissor blades or scissor legs arranged in an X-pattern at hinged pivot point intersections.

1. Extension of the Scissor Arms

When pressure is applied to the scissor legs through hydraulic cylinders, electric motors, or pneumatic pumps, the hydraulic fluid, compressed air, or electric current activates the lifting unit. The hydraulic cylinders, electric motors, or pneumatic system then pushes or pulls the scissor arms to fold inwards and extend outwards.

As the hydraulic cylinder pushes outwards or the electric motor drives the scissor arms, the scissor legs start to raise and get lifted.

The connected scissor blades fold and unfold at the pivot points, allowing the entire scissor lift structure to extend upwards and raise the attached load-bearing platform. This upward movement of the scissor lift provides vertical lifting capability.

2. Collapsing of the Scissor Arms

• When the pressure is released through the down or flow control valve, the hydraulic fluid, compressed air, or electric current stops pushing/pulling the scissor arms.
• The scissor legs then fold inwards at the hinged pivot point intersections.
• As the scissor arms fold, the entire scissor lift structure contracts and collapses vertically.
• This downward movement of the scissor lift lowers the work platform to the desired height with the help of the pantograph mechanism formed by the folding of connected scissor blades.
• The collapsing scissor mechanism enables precise lowering of the lift table and vertical movement using mechanical, hydraulic, or electric means for various applications.

3. Raising and Lowering the Platform

The scissor lift platform can be raised and lowered using various mechanisms to the required heights.

Applying Pressure to Raise

The scissor lift control system applies pressure to the scissor legs to raise the platform. In hydraulic scissor lifts, the operator turns the control lever, which activates the hydraulic pump.

The pump then pushes the hydraulic fluid through remote power packs and cylinders attached to the scissor legs. As the hydraulic cylinders extend outwards, pressure is exerted on the pivot points of the scissor arms.

This causes the scissor arms to fold inwards, and the entire scissor lift structure extends upwards. The connected scissor blades rise vertically along with the load-bearing work platform, providing access to higher areas.

Releasing Pressure to Lower

• The scissor lift operator releases the control lever to lower the platform, closing the flow control valve.
• This stops the hydraulic fluid supply from the remote power packs to the hydraulic cylinders.
• As the pressure is released, the cylinders start retracting inwards.
• The scissor arms then fold at the pivot points, and the entire scissor lift structure contracts vertically.
• The folding scissor blades’ pantograph mechanism allows the precise lowering of the larger work platform to the required height on the scissor lift base.
• This downward movement enables smooth up-and-down operation of the lifting unit using hydraulic, pneumatic, or electric means for industrial applications.

Safety Features

Scissor lifts are equipped with various safety features to prevent accidents at work sites.

Guardrails and Toeboards

Guardrails and toeboards are fitted around the entire perimeter of the scissor lift work platform. They are usually made of sturdy steel supporting beams. Guardrails provide support at waist height, while toeboards prevent tools and materials from falling off.

This protects lift operators and workers from falling hazards when the platform is raised to perform tasks at height on closed job sites or uneven terrain. The safety features help ensure proper safety for operating scissor lifts under all conditions.

Emergency Stop Buttons

Emergency stop buttons are fitted within easy reach on the scissor lift platform and control panel. In case of any unsafe situation, the scissor lift operator can immediately press these large red stop buttons to cut off power to the hydraulic, pneumatic, or electric systems.

This stops the upward or downward movement of the lifting unit, holding the work platform securely at that height. The emergency stop buttons form an essential safety feature, allowing operators to halt operations quickly in case of emergencies on the job site.

Overload Sensors

Overload sensors are installed on scissor lifts to prevent accidents from overloading. These sensors are calibrated to the lifting unit’s maximum lift capacity, which comprises hydraulic cylinders, electric motors, or pneumatic pumps.

If the weight on the platform exceeds the rated capacity when in operation, the sensors automatically detect the overload. This causes the lifting unit to stop raising or lowering the work platform, avoiding potential tipping over.

The sensors provide an additional safety feature, cutting off power to the hydraulic, electric, or pneumatic systems when overload is detected. This protects both equipment and operators working on the scissor lift.

Maintenance and Inspection

All equipment requires regular maintenance checks to ensure safe operation.

Regular Maintenance Tasks

Routine maintenance is essential on most scissor lifts, such as checking hydraulic fluid levels in cylinders, hoses, and remote power packs. The scissor lift operator also inspects hydraulic cylinders, electric motors, pneumatic pumps, and other components of the lifting unit.

Lubricating pivot points where the scissor arms fold and unfold prevent premature wear of these critical moving parts.

Inspecting hydraulic filters keeps the system clean for smooth operation. Performing these scheduled maintenance tasks according to manufacturer guidelines keeps the rough-terrain scissor lift functioning properly and ready to handle lifting mechanism tasks safely on job sites.

Inspection Requirements

• Scissor lifts must be inspected thoroughly during periodic inspections.
• The scissor mechanism, including scissor arms, pivot points, and cylinders, is checked for damage, cracks, or corrosion.
• Safety features like guardrails, toeboards, and emergency stop buttons are tested for proper functioning.
• Hydraulic systems are inspected for leaks in cylinders, hoses, remote power packs, and hydraulic fluid levels.
• Electrical systems on electric scissor lifts are examined for loose connections, damages, and proper grounding.
• Pneumatic components like pumps, valves, and air tanks are inspected for leaks and pressures.
• Operational testing of controls, lifting capacity, and emergency lowering are performed.
• Inspections ensure the identification of defects and safety compliance before further operation.

The Key Components of Scissor Lift

Let’s explore the main parts that make up a scissor lift.

The Platform

The platform is the load-bearing work surface area at the top of the scissor lift structure. It is made of sturdy materials like steel to withstand weights. The platform size can vary – smaller scissor lifts may have compact platforms, while larger ones have bigger platforms to accommodate more people and equipment.

Guardrails and toeboards are installed around the perimeter of the platform for safety. The folding scissor blades’ pantograph mechanism connects the platform to the lifting unit, enabling it to raise and lower vertically during the right scissor lift operation.

The Scissor Mechanism

The scissor mechanism is the critical component that enables the platform’s vertical movement. It comprises multiple connected scissor blades or scissor legs arranged in an X-pattern at hinged pivot point intersections.

The scissor legs fold and unfold to raise or lower the work platform through hydraulic, pneumatic, or electric means. This pantograph action of the scissor arms and legs transfers the lifting force to raise larger platforms vertically using the lifting unit.

Hydraulic or Electric Systems

The lifting unit of scissor lifts utilizes hydraulic, pneumatic, or electric systems to power the vertical movement of the platform. Hydraulic scissor lifts use a hydraulic pump, cylinders, hoses, fluid, and remote power packs to push or pull the scissor legs.

Electric scissor lifts contain an electric motor, controller, and rechargeable batteries that provide current to the scissor mechanism. Both systems precisely operate the folding and unfolding of scissor arms through hydraulic or electric means, raising and lowering the entire work platform as required.

Operating Controls

Operating controls are essential to raise scissor lifts safely and lower them. The electric scissor lift operator uses a control panel with buttons or levers to direct the lifting unit. In hydraulic scissor lifts, the operator turns a control lever to open or close the flow control valve, directing hydraulic fluid flow to cylinders.

Electric scissor lifts contain buttons to switch on the electric motor and select the upward or downward movement of the pantograph structure. Proper operator training is required before using these controls mounted on the platform or ground for rough terrain applications.

Benefits Of Using Scissor Lifts

Here are some possible benefits of using scissor lifts, including:

• Versatility: Rough terrain scissor lifts offer versatility in various work environments due to their easy navigation of challenging landscapes. Whether on construction sites or outdoor events, these lifts ensure smooth and stable operation, providing access to elevated areas that are otherwise difficult to reach.
• Enhanced Safety: The hydraulic scissor lift mechanism is robust and secure, ensuring operators and workers are safely elevated. Hydraulic and pneumatic scissor lifts, known for their powerful lifting capabilities, guarantee a stable platform for tasks at height. Electric scissor lifts eliminate the risks associated with diesel scissor lifts, making them the right choice for indoor applications where emissions need to be minimized.
• Increased Efficiency: Various scissor lifts, including electric, diesel, hydraulic, and pneumatic, are available so operators can choose the most suitable lift for their specific needs. Whether for indoor maintenance tasks or outdoor construction projects, these lifts offer efficient up-and-down movement, allowing workers to access elevated areas swiftly and safely.
• Flexibility in Operations: The scissor lift platforms provide a load-bearing platform attached to the scissor legs, which raises and lowers the scissor lift. This mechanism allows for precise positioning, making it ideal for tasks requiring accuracy and flexibility. Additionally, scissor lifts can be equipped with features like lift tables, enhancing their adaptability to job requirements.
• Cost-Effectiveness: Unlike boom lifts or aerial lifts, which may require additional space for operation and maneuverability, scissor lifts offer a more compact solution. Their mechanical scissor lift design and hydraulic or pneumatic pump systems reduce the need for extensive maintenance, leading to long-term cost savings.