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Home : Application Briefs : Mechanical/Hydraulic Model Used to Increase Loading Capacity of Hydraulic Scissor Lift

# Mechanical/Hydraulic Model Used to Increase Loading Capacity of Hydraulic Scissor Lift

The Challenge
Scissor lifts enable access to elevated work areas by raising a gantry with a scissor mechanism. The ascent is controlled with hydraulic cylinders actuated by fluid from a sump, while the descent is controlled by the slow release of the fluid back into the sump.

Scissor lifts are widely used in the construction industry and, accordingly, safety is critical in their design, manufacture, and operation.

The loading capacity of an existing scissor lift needs to be increased. To do this, elements of the lift, such as its hydraulic motor, are replaced with larger or more powerful components. In addition to increasing the capacity of the lift, the engineer must ensure that safe operating conditions are maintained for a given set of components. To do this, the engineer needs to determine the rates of ascent and descent and the forces and pressures generated in the hydraulic cylinders. Without computer simulation, this information cannot be obtained easily.
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The Solution

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An engineer uses MapleSim to build a model of the scissor lift. The engineer uses

• Multibody components to model the mechanical scissor mechanism;
• Hydraulic components to represent the hydraulic circuit;
• Signal-flow and logic components to control the pumping and release of the hydraulic fluid from the hydraulic cylinders during the ascent and descent phases.

Given the properties of the new components, the simulation enables the engineer to calculate the pressures and forces in the hydraulic cylinders.

The engineer can control the rate of descent by altering the open area of an orifice that chokes the flow of hydraulic fluid back into the sump, while the rate of ascent is controlled by the open area of a spool valve, along with the system pressure and cylinder dimensions. The effect of increasing the load on the gantry can also be investigated.

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