Machine Design

Safety in shock absorbers

Platinum shocks from Enidine Inc. are suited for areas with high humidity, harsh chemicals, and frequent wash downs. Shock absorbers can be used to decrease noise, damage, and vibration in machinery.

Companies striving to increase productivity by running machinery at higher speeds often end up with just more noise, damaged machinery and products, along with excessive vibration. At the same time, machine safety and reliability plummets. A variety of products such as rubber bumpers, springs, cylinder cushions, and shock absorbers are commonly used to solve these problems. However, they vary greatly in effectiveness and operation.

Rubber bumpers and springs, although inexpensive, have an undesirable recoil effect. Most energy absorbed at impact is actually stored. This stored energy is returned to the load, producing rebound and potential for damage to the load and machinery. Rubber bumpers and springs initially provide low resisting forces that increase with the stroke.

Cylinder cushions are limited in their range of operation. They are rarely capable of absorbing the energy generated by the system. By design, cushions have a relatively short stroke and operate at low pressures, resulting in little energy absorption. The remaining energy is transferred to the system, causing shock loading and vibration.

Shock absorbers however, provide controlled, predictable deceleration. They convert kinetic energy to thermal energy. More specifically, motion applied to the piston of a hydraulic shock absorber pressurizes the fluid in the shock and forces it to flow through restricting orifices, rapidly heating the fluid. Thermal energy is transferred to the shock absorber's body and harmlessly dissipated to the atmosphere.

It is important to understand the differences between standard automotive and industrial shock absorbers. Automotive shocks use deflective-beam-and-washer orificing. Industrial shocks use single orifice, multiorifice, and metering-pin configurations. Automotive shocks exert damping forces which vary in direct proportion to the velocity of the piston.

Damping forces in the industrial type however, vary in proportion to the square of the piston velocity.

In addition, damping forces in automotive shocks are independent of the stroke position. Damping force associated with industrial shocks can be either dependent or independent of stroke position.

This information provided by Enidine Inc., Orchard Park, N.Y.,

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