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How leak-free shock absorbers work

How leak-free shock absorbers work

Cushioneer shock absorbers, from Deschner Corp., Santa Ana, Calif., use a rolling diaphragm seal that makes the units leak free and allows the plunger rod to operate without friction. The diaphragm seal is attached to the shock’s plunger rod and inner body wall to eliminate any leakage path between them.

The high-pressure cylinder used in the shocks is hardened and honed to a mirror finish and individually mated to its piston within a nominal clearance of 0.0005 in. This metal-to-metal fit eliminates the need for a sliding piston seal.

The plunger rod extends instantaneously due to the internal fluid pressure and the absence of any sliding seals, which otherwise create fictional drag.  The main function of the spring is to keep the fluid pressurized so the diaphragm seal remains expanded, so it can roll back and forth smoothly.  The internal fluid pressure provides the plunger rod extension force.  Large, non-convoluted, return flow paths in conjunction with the free flowing balance poppet and check valve assure a rapid plunger rod return. 

Adjustable or self-adjusting

The adjustable Cushioneer has up to 25 variably spaced and sized ports drilled into the high-pressure cylinder.  When the moving load impacts the plunger rod, the fluid ahead of the piston can escape through all the ports.  As the plunger rod travels down the cylinder, the piston blocks successive ports, which increases the resistance and brings the load to a smooth stop.

The cylinder is assembled in the lower end of the body.When adjusting the Cushioneer, the cylinder is rotated within the body so that the ports are either closer to the wall (restricting the fluid flow and increasing the plunger rod resistance) or farther away from the wall (allowing freer fluid flow and less plunger rod resistance).  This adjustment design alters the flow restriction at all escape ports according to the effect each port has on the decelerating action.  The result is a smooth rate of deceleration at any setting.

The self-adjusting Cushioneer incorporates all the same features as the adjustable Cushioneer except the high-pressure cylinder in the self-adjusting model contains a pattern of grooves which the fluid bypasses the advancing piston.  The grooves are distributed over the length of the cylinder in a way that reduces the available bypass area as the piston travels farther.  The grooves are designed to maintain a constant flow rate under wide variations in impact energy and the changes in fluid pressure.  This allows the unit to automatically adjust to a wide range of impact loads and still provide a smooth stopping action.  The self-adjusting Cushioneer is intended for use in applications where the impact load fluctuates but a precise stopping point is required. 

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