Pneumatic And Hydraulic Equipment Page 426

RETURN An Airstroke actuator is a single acting device. To return the Airstroke to its minimum height (for another cycle or stroke), some return force must be used. Gravity acting on the load may be all that's required. The force to collapse the convoluted type Airstrokes to minimum height is given in the order block section for each part. If the load is not sufficient, then a second Airstroke or coil spring may be required. GUIDING An Airstroke follows the path of least resistance ; therefore, the actuator should be guided in most instances. This is often easily accomplished in the mounting geometry. HORIZONTAL MISALIGNMENT The upper and lower bead plate centers (or mounting plate centers in the case of a bead ring type attachment) may be out of line somewhat without injury to the bellows. Our "rule of thumb" for convoluted type Airstrokes is one inch misalignment allowed per convolution. So, a single convoluted air spring may be out of line by as much as 1 inch, a double by 2 inches, and a triple convoluted air spring by 3 inches. DESIGN ENVELOPE Adequate clearance should be provided around the Airstroke to prevent puncturing or rubbing of the bellows. The maximum diameter @ 100 psig for each Airstroke (bellows) is located just above the cross-sectional view of the air spring. FAIL SAFE DEVICES Some applications require the use of fail safe mechanisms (such as a mechanical lock-out on a scissors lift) to prevent damage or injury in the event of an air system failure. VACUUM An Airstroke can withstand a small amount of vacuum without injury to the bellows. The maximum amount of acceptable vacuum is dependent upon the bellows' size, the height in use, and whether it is a two ply or high strength (fabric) air spring. (A high strength Airstroke bellows has a "stiffer" wall than a two ply; therefore, it is less susceptible to dimpling and deformation inward). It is generally best to use only single convoluted air springs under vacuum. STACKING It is permissible to stack Airstrokes (one on top of another) to increase stroke; however, the center plate (or plates) connecting the two or more Airstrokes MUST BE GUIDED. Please note that the air spring forces are not additive in this configuration. A method for guiding, which also illustrates one center ring concept for mounting the two parts together at the middle, is illustrated below: Customer Must Supply Button Head-Socket Head Cap Screws Center Ring ACTUATORS - ISOLATORS Firestone (314) 427-0600 800-444-0522 (FAX) 314-427-3502 www. j JHF Catalog [ Volume 7 ] 426 Prices Subject to Change Without Notice John Henry Foster pneumatic and hydraulic equipment

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