Severe vibration inputs to a relatively sensitive object are often attenuated by a base isolation or isolated platform system. The object to be protected is placed on a foundation or platform that is free to move in the direction of the vibratory input, and springs or spring-damper combinations are added between the isolated object and the source of the vibration. In the case of multi-axis vibrations, the isolators must be located such that they respond to all of the possible input directions.
If the input is in a relatively narrow frequency band with no shock inputs, then in many cases springs alone will provide the desired isolated response. However, if the vibratory input is broad band or includes various types of transients, such as shock or start-up and shut-down cycles, damping will be required to eliminate over-stroking the spring elements from the shock or possible short duration resonance. Materials with inherent structural damping, such as elastomers and laminates, rarely provide more than 5% critical damping – a value that does not reduce the transient motions sufficiently. Added fluid damping products can provide the required damping levels, but often prove difficult to package. A solution now exists for this type of design problem – Modular Spring-Damper Vibration Isolators from Taylor Devices, Inc.
Originally developed for the U.S. Navy, Taylor Devices’ Modular Spring-Damper Vibration Isolators are now commercially available for industrial and civil engineering applications.
These products are available in numerous sizes and several forms, including:
Damping – single or double acting
Spring – single acting or self-centering with bi-directional output
All products combine the spring and damping elements into one compact, easy to install, modular strut. Depending on spring force and rate requirements, spring types include mechanical, elastomer, or hydraulic. Because of the high capacity of the fluid damping elements, damping ratios of 25 to 75% critical damping can be easily obtained, providing optimum performance.
Available sizes range from 200 lbs. to 1,000 tons of force, with strokes of up to plus or minus 40 in. Applications vary widely, from platform isolation for small electronics modules to earthquake protection on long span highway bridges.