Firestone EMDG198 Horizontal Misalignment, Design Envelope, Stacking, Fail Safe Devices, Vacuum

Angular Capability continued

These measurements must fall within the guide lines for that particular part. Consider style #22 in the following scissors arrangement:

Calculate
Force Here			Max Ht
Max Ht		#22	(Must be ≤ 10.1)
(Must be ≥	3.0)
Pivot
Point

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:

Bellows must

not rub against

itself here.

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.

STACKING

It is permissible to stack Airstrokes (one on top of another) to increase stroke; however, the center plate (or plates) connect- ing 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:

Center Ring

Customer Must

Supply Button

Head-Socket Head

Cap Screws

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 vacu- um 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.

An Airstroke Design Parameter Worksheet can be found on page 103.

16