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Cushioned Cylinders

Category: 
Cylinder Tech Tips

Cushioned Cylinders

Features:

• Easily accessible, stainless steel needle for fine adjustment of cushion
• Needle cannot be removed
• Long-lasting Buna-N cushion seal
• Cushions the last 1/2" of stroke

 

 

• Available at either end or both ends of the cylinder
• Available with magnetic pistons
• Bumpers included on the non-cushioned end of the 1 1/16" and 1 1/2" bore cylinders with only one cushion

In fast cyling applications, cushioned cylinders provide superior life and a better machine environment. The pneumatic cushions decelerate the piston and rod assembly at the end of the cylinders travel, reducing internal impact force/noise and enabling faster piston velocities. A cushion spear/nose is located on either or both sides of the piston, depending on which cushion option is selected. The cylinder's heads have a cushion pocket with a cushion seal. When the cushion spear enters the cushion seal, the air exiting the cylinder is trapped, causing it to compress. This provides a resistance force that decelerates the piston. The cushion seal collapses when air coming through the adjacent port is introduced, allowing for a fast breakaway.




A needle valve in the head provides a parallel path for the air to exit. Clippard's needle design has a high flow gain, allowing the user to fine-tune the cushion's effectiveness­ anywhere from little effect to actually stopping the cylinder.
Cushioned cylinders are not designed to decelerate machine members or to take the place of shock absorbers in applications with high kinetic energy. Cushions cannot be added to existing cylinders (requires additional components and machining).

Note: C option cannot be ordered with B option (bumpers).

 


When the piston moves to the left in a pneumatic cylinder, the air on the left side of the piston in the left chamber must be exhausted to allow full travel of the piston and rod. In a cushioned cylinder (see example above), this air cannot escape from the port by virtue of the cushion seal which seals against the piston rod. The only escape path is through the cushion orifice, which is normally a very small hole. This hole leads to a cushion needle, which may be adjusted to vary the opening into the exhaust port that leads to the port. Normally, the port is connected to a control valve that allows the air to be exhausted to the atmosphere. As the piston moves to the left, it initially moves very rapidly as air on its left side is allowed to exhaust from the port. When the piston rod reaches the cushion seal, the piston travel is slowed down due to the cushioning of the air. This last portion of the cylinder stroke can be adjusted using the cushion needle—from nearly full speed, to a very slow end of stroke speed.