Pneumatic And Hydraulic Equipment Page 427

SELECTION 1. Refer to the selection guide for Airstroke force and stroke capabilities. After your list of possibilities has been reduced to one or two air springs, then turn to the individual data page for more detailed information on those parts. 2. STROKE: The maximum STROKE CAPABILITY is the difference between the height corresponding to the "start of the shaded area" minus the minimum height. This entire stroke, or any portion thereof , may be used. If an internal rubber bumper is required, please note that the minimum height is increased, and therefore, the total stroke is decreased. 3. FORCE: Read the forces directly from the static data chart, or, use the force table located under the chart. Notice that the force generally decreases as height increases. 4. SELECT THE END CLOSURES AND AIR INLET SIZE: Most Airstroke actuators are available with permanently attached plates or bead ring attachments. If an alternate end closure option is available, it is so stated under the cross sectional view of the part. DOWN AND UP STOPS Positive stops in both directions (compression and extension) should always be used with Airstroke actuators . 1. In COMPRESSION, the minimum height shown for each air spring is at, or slightly above the PINCH POINT of the bellows. Here is a #22 shown in the collapsed or "pinch point" condition: The bellows can be damaged if allowed to constantly bottom out as shown above; therefore, a downstop is required to prevent this. An external downstop can be something as simple as a steel block and should be sized at or slightly greater than the minimum height of the Airstroke. In our #22 example, the block would need to be at least 3.0 inches high. If an external downstop cannot be used, many parts are available with internal rubber bumpers (shown as a dotted line in the cross-sectional view of the air spring where available). 2. In EXTENSION, an upstop is required to prevent the air spring from overextending at heights into the shaded area of the graph. The reasons for this are twofold: a) the life of the bellows may be reduced and b) the crimp may open up, allowing the bellows bead to blow out of the metal end closure. There are many ways to design-in an upstop, including a. a chain, b. a cable, c. contacting a metal stop, etc. ANGULAR CAPABILITY An Airstroke actuator can stroke through an arc (without a clevis). Angular motion of up to 30 degrees is possible. When using an actuator with the mounting plates at an angle to each other, observe the following: a. Measure force at the height between the plate centers. b. Measure maximum height at the side separated the furthest. c. Measure minimum height at the side collapsed the most. These measurements must fall within the guide lines for that particular part. Consider style #22 in the following scissors arrangement: Reversible sleeve Type 1T parts may also stroke through an arc. In this case, care must be taken to prevent the bellows from rubbing (internally) against itself where it rolls over the piston: 3.0 Bellows must not rub against itself here. Pivot Point #22 Max It (Must be 10.1) Max It (Must be 3.0) Calculate Force Here F I R E S T O N E ACTUATORS - ISOLATORS Firestone JHF Catalog [ Volume 7 ] (314) 427-0600 800-444-0522 (FAX) 314-427-3502 www. j hf.com 427 Prices Subject to Change Without Notice John Henry Foster pneumatic and hydraulic equipment

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