5 Common structure types

5.1 Structure type of commonly used compression gas spring (YQ) series

See Figure 1 for structure type of commonly used compression gas spring (YQ) series.

Key 1  piston rod2  guide3  seal4  piston

5  cylinder6  gas chamber7  oil8  spacer

Figure 1 Schematic diagram of commonly used compression gas spring

5.2 Structure type of commonly used lockable gas spring (KQ)

5.2.1 Structure type of rigid lockable gas spring in the extension direction

See Figure 2 for Structure type used in rigid lockable gas spring in the extension direction.

Key1  piston rod module2  guide3  seal4  oil

5  piston module6  cylinder7  gas chamber

8  separator piston module9  valve pin10  spacer

Figure 2 Schematic diagram of rigid lockable gas spring in the extension direction

5.2.2 Structure type of rigid lockable gas spring in the compression direction

See Figure 3 for the Structure types of rigid lockable gas spring in the compression direction.

Key1  piston rod module2  guide3  seal

4  oil5  piston module6  cylinder

7  valve pin8  separator piston module9  gas chamber

Figure 3 Schematic diagram of rigid lockable gas spring in the compression direction

5.2.3 Structure type of elastic lockable gas spring

See Figure 4 for the Structure type of elastic lockable gas spring.

Key1  piston rod module2  guide3  seal4  oil5  piston module

6  cylinder7  gas chamber8  valve pin9  spacer

Figure 4 Schematic diagram of elastic lockable gas spring

5.3 Structure type of commonly used chair height adjustment gas spring (ZSQ)

5.3.1 Structure type of elastic lockable chair height adjustment gas spring

See Figure 5 for the Structure type of elastic lockable chair height adjustment gas spring

Key1  starting lever2  starting lever retainer3  valve4  valve pin5  guide of standing tube6  gas chamber7  standing tube

8  cylinder (inner cylinder)9  piston rod10  outer tube11  inner cylinder retainer12  seal13  guide

Figure 5 Schematic diagram of an elastic lockable chair height adjustment gas spring

5.3.2 Structure type of rigid lockable chair height adjustment gas spring

See Figure 6 for the Structure type of rigid lockable chair height adjustment gas spring

Key1  starting lever2  starter lever retainer3  valve4  valve pin5  guide of standing tube6  oil chamber7  standing tube8  separator piston module

9  cylinder (inner cylinder)10  piston rod11  outer tube12  gas chamber13  ventilation support14  seal15  guide

Figure 6 Schematic diagram of rigid lockable chair height adjustment gas spring

5.4 Structure type of commonly used stretching gas spring

5.4.1 Structure type of ordinary stretching gas spring (LQ)

See Figure 7 for the Structure type of ordinary stretching gas spring (LQ)

Key1  piston rod2  guide3  seal

4  gas chamber5  cylinder6  piston module

Figure 7 Schematic diagram of an ordinary stretching gas spring

5.4.2 Structure type of lockable stretching gas spring (KLQ)

See Figure 8 for the Structure type of lockable stretching gas spring (KLQ)

Key1  guide2  seal3  spacer4  piston rod module5  gas chamber

6  piston module7  guide seal of joint rod8  differential pressure joint rod9  cylinder

Figure 8 Schematic diagram of lockable stretching gas spring

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).

Foreword  

SAC/TC 235 is in charge of this English translation, in case of any doubt about the contents of English translation, the Chinese original shall be considered authoritative.

This document is drafted in accordance with the rules given in the GB/T 1.1—2009 Directives for standardization— Part 1: Structure and drafting of standards.

This document was proposed and prepared by SAC/TC 235 (National Technical Committee 235 on Spring of Standardization Administration of China).

Gas spring design calculation (English version of national strandard, initiated by LeiYan Gas Springs)

1 Scope

This document specifies parameter names, symbols, descriptions and units of gas spring, as well as commonly used structure types, design calculation principles and design calculations.

This document is applicable to compression gas spring, lockable gas spring, chair height adjustment gas spring and stretching gas spring. Other gas springs may also be used in accordance with this standard.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 2348, Fluid Transmission System and Component, Diameter of Cylinder and Piston Rod

3 Terms and definitions

For the purposes of this document,the following terms and definitions apply.

3.1

Gas spring

An elastic device consisting of an enclosed cylinder and a sliding piston and piston rod model with nitrogen or other inert gas used as the energy storage medium.

3.2

Compression gas spring

A gas spring in which the piston rod is in a freely extended state without external force and is subjected to pressure force.

3.3

Lockable gas spring

A gas spring that can be locked or unlocked at any position during the motion stroke.

3.4

Chair height adjustment gas spring

A gas spring used for chair height adjustment, which can be locked or unlocked at any position during the motion stroke.

3.5

Stretching gas spring

A gas spring in which the piston rod is free to resilience without external force and is subjected to tensile force.

4 Parameter names, symbols, descriptions and units

See Table 1 for gas spring parameter names, symbols, descriptions and units.

Table 1

Parameter name	Symbol	Description	Unit
design stroke	S	Axial length of the piston rod from full extension (or tension) to full compression (or resilience)	mm
working stroke	S1	The length between the maximum extension (or tension) and the minimum extension (or tension) of the gas spring in working condition
safe stroke	S2	Safe margin for the required working stroke: S2 = S – S1
extended length	L	Length of the gas spring at full extension (or tension)NOTE  The extended length of the stretching gas spring is the length in the stretched condition.
rod end length	L1	Connection length of the gas spring rod end
cylinder end length	L2	Connection length of the gas spring cylinder end (chair height adjustment gas spring L2 = 0).
gas chamber length	L3	Gas chamber length of gas spring
cylinder length	B	Cylinder length of gas spring
guide length	H	Guide length of gas spring
piston rod diameter	d	Piston rod diameter of gas spring
inner diameter of hollow piston rod	d0	Inner diameter of hollow piston rod of lockable gas spring
valve pin diameter	d1	Effective diameter of gas spring valve pin
cylinder inner diameter	D1	Inner diameter of gas spring cylinder
cylinder outer diameter	D2	Outer diameter of gas spring cylinder
outer diameter of outer tube	D3	Outer diameter of outer tube of chair height adjustment gas spring
outer diameter of standing tube	D4	Outer diameter of standing tube of chair height adjustment gas spring
thickness of cylinder	δ1	Thickness of gas spring cylinder: δ1 = (D2 – D1)/2
thickness of hollow piston rod	δ2	Thickness of hollow piston rod of gas spring: δ2 = (d – d0)/2
thickness of outer tube	δ3	Thickness of outer tube of chair height adjustment gas spring
thickness of standing tube	δ4	Thickness of standing tube of chair height adjustment gas spring
center of gravity distance	l	Distance from the centre of gravity of the subject supported by gas spring to the centre of gyration	mm
arm of force	b	Arm of force of the gas spring when the lever arm is extended
radius of gyration	K	Radius of gyration of the cross section of the gas spring piston rod
cross section area	A	Cross section area of the gas spring piston rod	mm2
moment of inertia	J	Moment of inertia of the cross section of the gas spring piston rod	mm4
unlocking force	Fk	Force required to unlock the valve pin in order to unlock the gas spring	N
minimum extension force	F1	During extension, the force at the specified measuring point C1 from the beginning of the working stroke
maximum extension force	F2	During extension, the force at the specified measuring point C1 from the end of the working stroke
minimum compressive force	F3	During compression, the force at the specified measuring point C1 from the beginning of the working stroke
maximum compressive force	F4	During compression, the force at the specified measuring point C1 from the end of the working stroke
minimum tension force	F5	During the tension process, the force at the specified measuring point C1 from the beginning of the working stroke

Parameter name	Symbol	Description	Unit
maximum tension force	F6	During the tension process, the force at the specified measuring point C1 from the end of the working stroke	N
minimum resilience force	F7	During the resilience process, the force at the specified measuring point C1 from the beginning of the working stroke
maximum resilience force	F8	During the resilience process, the force at the specified measuring point C1 from the end of the working stroke
nominal force a	Fa	The average of the minimum extension force and the minimum compress force, i.e.: Fa = (F1 + F3)/2. Or the average of the minimum tension force and the minimum resilience force, i.e.: Fa = (F5 + F7)/2.The “nominal force a” is one of the indicators of the comprehensive characteristics of a gas spring
nominal force b	Fb	The average of the maximum extension force and the maximum compress force, i.e.: Fb = (F2 + F4)/2. Or the average of the maximum tension force and the maximum resilience force, i.e.: Fb = (F6 + F8)/2.The “nominal force b” is generally used in the calculation of the resilience force ratio	N
specified force	Fx	The forces (F1, F2, F3…) marked on the products and drawings agreed between supplier and vendor
dynamic friction force	Fr	The average of the difference between the minimum compress force and the minimum extension force, or the average of the difference between the minimum tension force and the minimum resilience force
valve pin friction	fr	Normally the friction generated by the valve pin is 10 to 30
gravity	G	Gravity of the object supported by the gas spring	N
permissible critical force	FL	Permissible critical force of the gas spring piston rod
pressure	P	Pressure within the gas spring	MPa
maximum pressure	Pmax	Maximum pressure within the gas spring in working condition
modulus of elasticity	E	Modulus of elasticity of the material, for steel using 2.1 x 105
allowable stress	[σ]	Allowable stress of material
test value of material strength	f	Test value of material strength, for steel using 490
force ratio	α	Ratio of nominal force b to nominal force a, i.e., α = Fb/Fa	——
radius ratio	r	Ratio of cylinder outer diameter to inner diameter
safety factor	n	Safety factor for piston rod stability, which is generally n ≥ 1.4
installation coefficient	m	Installation coefficient of gas spring
temperature coefficient	o	Compensation coefficient for demanded force affected by temperature changes of the gas spring working environment , which is generally 1.1 to 1.25
number	i	Number of gas springs
measuring point	C1	The measuring point of the force during dynamic or static measurement, which is generally S ≤ 80 mm, C1 = 5 mm; S > 80 mm, C1 = 10 mm	mm

Table 1 (continued)