7.3 Stroke S and extended length L

7.3.1 Schematic diagram of the overall dimensions of gas spring

See Figure 11 to Figure 14 for the basic dimensions (stroke S, extended length L, etc.) of common gas springs, including compression gas spring, lockable gas spring, chair height adjustment gas spring and stretching gas spring.

Figure 11 Schematic diagram of the dimensions of compression gas spring

Figure 12 Schematic diagram of the dimensions of lockable gas spring

NOTE  In a chair height adjustment gas spring, B refers to the outer tube length.

Figure 13 Schematic diagram of the dimensions of chair height adjustment gas spring

Figure 14  Schematic diagram of the dimensions of stretching gas spring

7.3.2 Design of the gas spring stroke S

When designing the stroke of different types of gas springs, safe stroke should be considered. For details, please refer to the 7.3.1 schematic diagram of the overall dimensions of gas spring (Figure 11 to Figure 14) and calculate according to formula (14):

 ………………(14)

For ordinary compression gas spring and stretching gas spring S₂ ≥ 5 mm; for lockable gas spring and chair height adjustment gas spring S₂ ≥ 2 mm.

7.3.3 Definition of the extended length L

According to the 7.3.1 schematic diagram of the overall dimensions of a gas spring (Figure 11 to Figure 14), the extended length L is calculated according to formula (15):

 ………………(15)

7.4 Design calculation of piston rod

7.4.1 Overview

The diameter of the gas spring piston rod should be decided according to GB/T 2348, and the recommended piston rod diameter d should be 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 20 mm, or calculated according to 7.4.2 and 7.4.3. The calculation results should refer to Annex C, or be agreed between supplier and vendor. The thickness of hollow rod δ₂ should not be less than 2 mm.

7.4.2 Calculation of solid piston rod

7.4.2.1 The diameter d of the solid piston rod of compression gas spring and chair height adjustment gas spring is generally calculated according to formula (16):

………………(16)

7.4.2.2 When the length of the solid piston rod is less than or equal to 10 times of piston rod diameter d, the diameter d is calculated according to formula (17). While the allowable stress of the gas spring piston rod is decided according to Table D.1 of Annex D:

………………(17)

7.4.2.3 The diameter d of the solid piston rod of a stretching gas spring is calculated according to formula (18):

………………(18)

7.4.3 Calculation of hollow piston rod

7.4.3.1 The piston rod of the lockable gas spring is usually a hollow piston rod, and its diameter d is generally calculated according to formula (19):

………………(19)

7.4.3.2 When the length of the hollow piston rod is less than or equal to 10 times of piston rod diameter d, the diameter d is calculated according to formula (20). While the allowable stress of the gas spring piston rod is decided according to Table D.1:

………………(20)

7.4.4 Verification of piston rod stability

The stability of the piston rod can be verified according to Annex E.

Gas spring design calculation (English version of national strandard, initiated by LeiYan Gas Springs), proposed and prepared by SAC/TC 235 (National Technical Committee 235 on Spring of Standardization Administration of China).