Control Task: A double-acting hydraulic cylinder should extend and clamp a workpiece upon actuating a pushbutton valve. The cylinder should remain in the clamping position as long as the valve is actuated. If the pushbutton is released, the cylinder should retract. To achieve this, a hydraulic circuit is developed, with a fixed-displacement hydraulic pump serving as the powerful and reliable power source. The system is designed to set the maximum pressure (200 bar), ensuring safety and efficiency. Develop a hydraulic circuit to realize the control function.

Control of a Double-acting Hydraulic Cylinder Using a 4/2-DC Valve

Explanation: The double-acting cylinder can be controlled by using the manually-actuated 4/2-DC valve. The power supply unit comprises a hydraulic pump and an integral pressure relief valve (PRV). The pump delivers pressurized fluid to the circuit with a constant-displacement. The integral pressure relief valve limits the maximum pressure rating of the power pack. The operating pressure in the system can be set by using a separate pressure relief valve (PRV).

When the valve is actuated, fluid flow is directed to the piston-side (cap-end) port of the cylinder, which then extends. In the normal position of the DC valve, fluid flow is directed to the piston-rod-side (head-end) port of the cylinder, which retracts to its home position.

Applications: Hydraulic cylinders have various applications across different industries. They are used in material handling for controlling the lifting and tilting of forks. In injection molding machines, hydraulic cylinders are used to manage the injection process and clamping mechanisms. Excavators and backhoes utilize hydraulic cylinders for digging, lifting, and moving materials. They also play a role in tractors for implementing control and steering, as well as in press machines for metal forming and stamping. Hydraulic cylinders are essential in mining equipment to control drilling operations and are employed in automotive applications for brakes and suspension systems. In marine applications, they are used to control rudder position and operate winches and cranes. In the aerospace industry, hydraulic cylinders are employed to extend and retract the landing gear and adjust the position of control surfaces. These diverse applications benefit from the precise control and powerful force that double-acting hydraulic cylinders provide.

Maintenance of Hydraulic Cylinders (for guidance):

– Check piston and piston rod for wear, dents, damages, nicks, scoring and pitting

– Check for roundness and straightness of the barrel wear

– Control internal and external fluid leakages

– Replace gaskets and tighten end plates

– Replace leaking piston & piston-rod seals, and bushing

– Align cylinder and mating part

– Check for loose or deformed rod eyes

– Check for sluggish/erratic operation and creeping

– Check mountings for looseness and cracks

– Open bleed ports

By

Joji Parambath

Resource Person / Author

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