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Terms, Definitions of lockable gas spring
3. Terms, Definitions, Symbols, and Explanations
The terms, definitions, symbols, and explanations established in GB/T 1805 and Table 1 apply to this standard.
| Term | Definition or Explanation | Symbol | Unit |
| Gas spring | An elastic element composed of a sealed cylinder barrel, a piston that can slide inside the cylinder barrel, and a piston rod assembly, using nitrogen or other inert gases as the energy – storage medium. Note: Adapted from GB/T 1805—2001, Definition 2.9 | ||
| Lockable gas spring | A gas spring that can be locked or unlocked at any position within its movement stroke | ||
| Piston rod diameter | The diameter of the piston rod of a gas spring [GB/T 1805—2001, Definition 3.111] | d | mm |
| Cylinder inner diameter | The inner diameter of the cylinder barrel of a gas spring | D1 | mm |
| Cylinder outer diameter | The outer diameter of the cylinder barrel of a gas spring [GB/T 1805—2001, Definition 3.110] | D2 | mm |
| Stroke | The axial displacement of the piston rod from the fully extended state to the state when compressed to the minimum size | S | mm |
| Extended length | The effective length of a gas spring in the fully extended state | L | mm |
| Unlocking force | The force required to release the locked state of a gas spring and open the valve | Fk | N |
| Start – up force | The initial force required to press the piston rod after opening the valve, when the gas spring has been in the extended state for a certain period of time [GB/T 1805—2001, Definition 3.116] | F0 | N |
| One cycle | The piston rod is compressed and extended once each according to the specified stroke | ||
| Extension speed | The average speed at which the piston rod freely extends from the end of the specified stroke to the initial position | v – | mm/s |
| Specified force | The force marked on the product drawings and products confirmed by both the supplier and the demander (F1, Fa, F3, …) | F× | N |
| Minimum extension force | The force measured at the specified force – taking point C near the starting point of the working stroke during the extension process. Note: Adapted from GB/T 1805—2001, Definition 3.119 | F1 | N |
| Maximum extension force | The force measured at the specified force – taking point C near the end point of the working stroke during the extension process. Note: Adapted from GB/T 1805—2001, Definition 3.120 | F2 | N |
| Minimum compression force | The force measured at the specified force – taking point C near the starting point of the working stroke during the compression process. Note: Adapted from GB/T 1805—2001, Definition 3.121 | F3 | N |
| Maximum compression force | The force measured at the specified force – taking point C near the end point of the working stroke during the compression process. Note: Adapted from GB/T 1805—2001, Definition 3.122 | F4 | N |
| Nominal force a | One of the comprehensive characteristic indicators of a gas spring. It is the average value of the maximum extension force and the minimum compression force, i.e., Fa=(F1 + F3)/2. Note: Adapted from GB/T 1805—2001, Definition 3.123 | Fa | N |
| Nominal force b | The average value of the minimum extension force and the maximum compression force, i.e., Fb=(F2 + F4)/2. Nominal force b is generally used for calculating the force ratio | Fb | N |
| Dynamic friction force | The average value of the difference between the minimum compression force and the minimum extension force, i.e., Fr=(F3 – F1)/2. Note: Adapted from GB/T 1805—2001, Definition 3.124 | Fr | N |
| Force ratio | The ratio of nominal force b to nominal force a, i.e., α = Fb/Fa. Note: Adapted from GB/T 1805—2001, Definition 3.125 | α | |
| Rigid locking | In the locked state, when a gas spring is under the action of axial compression and tension forces, the piston rod generates displacement, and its force – displacement characteristic curve is as follows. | ||
| Elastic locking | In the locked state, when the displacement of the piston rod of a gas spring under the action of compression or tension forces is not more than 2mm, it can reach the agreed locking force (see Curves I and II). In the locked state, when the piston rod of a gas spring under the action of compression or tension forces generates a relatively large displacement (see Curve III) | ||
| Locking force | The axial compression or tension force required to cause a certain displacement of the piston rod when the gas spring is in the locked state | Fs | N |
| Force – taking point | The point for collecting force values during dynamic or static testing | C | mm |
Technical Specification for Lockable Gas Springs (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).
Technical Specifications for Lockable Gas Spring
Lockable Gas Springs
1. Scope
This standard specifies the terms and definitions, markings, technical requirements, test methods, inspection rules, as well as the requirements for identification, packaging, transportation, and storage of lockable gas springs (hereinafter referred to as “gas springs”).
This standard is applicable to angle – adjustable lockable gas springs and other forms of lockable gas springs except for seat – lifting lockable gas springs, which use nitrogen or other inert gases as the energy – storage working medium.
Seat – lifting lockable gas springs are not applicable to this standard.
2. Normative Referenced Documents
The provisions of the following documents are incorporated into this standard by reference. For dated references, subsequent amendments (excluding corrigenda) or revised editions do not apply to this standard. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the latest versions of these documents. For undated references, the latest version applies to this standard.
- GB/T 1771 Paints and varnishes – Determination of resistance to neutral salt spray (GB/T 1771—2007, ISO 7253:1996, IDT)
- GB/T 1800.1 Geometrical product specifications (GPS) – Limits and fits – Part 1: Bases of tolerances, deviations and fits (GB/T 1800.1—2009, ISO 286 – 1:1988, MOD)
- GB/T 1805 Spring terms
- GB/T 2348 Hydraulic fluid power systems and components – Cylinder bores and piston rod diameters (GB/T 2348—1993, neq ISO 3320:1987)
- GB/T 2349 Hydraulic fluid power systems and components – Cylinder piston stroke series
- GB/T 2828.1 Sampling procedures for inspection by attributes – Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot – by – lot inspection (GB/T 2828.1—2003, ISO 2859 – 1:1999, IDT)
- GB/T 2829 Sampling procedures and tables for inspection by attributes for periodic inspection of stability of processes
- GB/T 10125 Corrosion tests in artificial atmospheres – Salt spray tests (GB/T 10125—1997, eqv ISO 9227:1990)
- QC/T 484 Automotive paint coatings
- QC/T 625 Coatings and chemical treatment layers for automobiles
Technical Specification for Lockable Gas Springs (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).
Identification, Packaging, Transportation, and Storage of compression gas spring
9. Identification, Packaging, Transportation, and Storage
9.1 Safety Identification
Each gas spring product must be marked with a safety identification in an obvious position.
9.2 Product Identification
Each gas spring product shall be marked with the following contents agreed upon by the supplier and the demander in an obvious position:
a) The trademark of the demander or the supplier;
b) Product code, model, or part number;
c) The name, code of the supplier or the name of the demander;
d) Delivery date or production batch number.
9.3 Packaging Box Identification
The packaging box of the gas spring shall be marked with the following contents agreed upon by the supplier and the demander:
a) Product name, model, part number, order number, or bar code;
b) The name, code, or address of the supplier and the demander;
c) Quantity of products;
d) External dimensions, gross weight, net weight;
e) Production date;
f) Markings such as “Beware of High Temperature” and “Handle with Care”.
9.4 Packaging
- 9.4.1 There shall be flexible material protection between each gas spring in the packaging box.
- 9.4.2 The gross weight of each box shall not be greater than 30 kg.
- 9.4.3 The packaging box shall be accompanied by a certificate of conformity stamped by the quality department.
- 9.4.4 The material of the packaging box shall be agreed upon by the supplier and the demander.
9.5 Transportation
The gas springs shall be shipped by the transportation method agreed upon by the supplier and the demander.
9.6 Storage
Gas spring products shall be stored in a dry and ventilated warehouse, and there shall be no acid, alkali, or other corrosive gases around. Under normal storage conditions, there shall be no rust on the plating layer or peeling of the paint within one year, and the attenuation of the nominal force value shall not be greater than 5%.
Technical Specification for Compression Gas Springs (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).
Inspection Classification of compression gas spring
8.3 Inspection Classification
Product inspections are divided into factory inspections and type inspections.
- 8.3.1 Factory Inspections
All products must undergo final inspections before delivery. The inspection items are shown in Table 5.
| Inspection Items | Inspection Type | Inspection Methods and Requirements |
|—|—|—|
| Specified Force Value | Mandatory Inspection | Shall comply with the provisions of Table 2 |
| Appearance | Mandatory Inspection | Conducted according to 7.1.2, shall comply with the provisions of 6.1.3 – 6.1.5 and 9.1 |
| Extended Length | Sampling Inspection according to 8.2 | Conducted according to 7.1.1, shall comply with the provisions of 6.1.2 |
| Force Characteristic Curve | Sampling Inspection according to 8.2 | Conducted according to 7.2, shall comply with the provisions of 6.2 | - 8.3.2 Type Inspections
Type inspections shall generally be carried out under any of the following circumstances:- a) When new products or old products are transferred to production and undergo finalization appraisal;
- b) When there are major changes in product design, structure, materials, or processes;
- c) When there are major changes in key process equipment or personnel;
- d) After a certain period of normal production of series products;
- e) When major quality problems occur in products;
- f) When products are out of production for more than one year and then resume production;
- g) When there are significant differences between the results of factory inspections and the previous type inspections;
- h) When the national quality supervision agency requires type inspections.
The type tests in d) and h) shall be carried out according to 8.2. Other type inspections shall be carried out in accordance with the provisions of GB/T 2829. 6 gas springs are sampled and divided into 3 groups, with 2 gas springs in each group. The inspections are carried out as shown in Table 6.
| Group | 1 | 2 | 3 |
|—|—|—|—|
| Inspection Items | Force characteristics 6.2, High and low temperature resistance performance 6.4, Cycle life 6.5, Tensile resistance performance 6.6
Corrosion resistance performance 6.7 | Dimensions 6.1.2
Appearance quality 6.1.3, 6.1.4, 6.1.5
Safety identification 9.1 | – |
| Number of Samples | 2 | 2 | 2 |
| Discrimination Level | I | I | I |
| Judgment Array | [0,1] | [0,1] | [0,1] |
| Unqualified Quality Level (RQL) | 40 | 40 | 40 |
Technical Specification for Compression Gas Springs (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).
Inspection Rules of Compression Gas Spring
8. Inspection Rules
8.1 Defects
Gas springs that do not meet the technical requirements specified in the product technical standards and drawings are considered defective. According to the severity of the defects, they are divided into:
a) A – Critical defects;
b) B – Major defects;
c) C – Minor defects.
The defect items are shown in Table 4.
| A Critical Defect Items | B Major Defect Items | B Major Defect Items | C Minor Defect Items |
| High and low temperature resistance performance 6.4 Cycle life 6.5 Tensile resistance performance 6.6 | Dimensions Force characteristics Corrosion resistance performance | 6.1.2 6.2 6.7 | Appearance quality 6.1.3, 6.1.4, 6.1.5 Safety identification 9.1 |
8.2 Sampling Methods
- 8.2.1 Inspection Lots
- a) The inspection lot must be qualified gas spring products. 280 gas springs are regarded as one inspection lot. If the number of products is greater than 280, the inspectors shall arbitrarily divide them into several inspection lots of 280 pieces each, and then randomly select one inspection lot as the sampling object.
- b) If the number of products is less than 280, it is not suitable to be sampled as an inspection lot. Instead, inventory products should be selected for sampling, or the corresponding code letter and sample should be selected in Table 1 of GB/T 2828.1 according to the actual lot size.
- 8.2.2 Sample Selection
- 8.2.2.1 Non – destructive inspection items share one sample. If the number of products is greater than 150, according to the general inspection level I specified in GB/T 2828.1, with the sample size code letter E, and according to the normal inspection single – sampling plan, 13 gas springs are sampled. If the number of products is not more than 150, the sample shall be selected according to 8.2.1 b).
- 8.2.2.2 High and low temperature resistance performance, cycle life, tensile resistance performance, and corrosion resistance tests are destructive tests and belong to type – test items. During inspection, according to the special inspection level S – 1 specified in GB/T 2828.1, with the sample size code letter B, and the normal inspection single – sampling plan, the force characteristics, high and low temperature resistance performance, cycle life, and tensile resistance performance tests share one set of samples, and the corrosion resistance performance test uses one set of samples. 3 gas springs are sampled for each.
- 8.2.3 Acceptable Quality Limit (AQL) and Acceptance Number (Ac)
The acceptable quality limit for A – defect items and B – defect items is 4.0, and the acceptance number is 0.
The acceptable quality limit for C – defect items is 6.5. When the code letter is E, the acceptance number is 2; when the code letter is D, the acceptance number is 1. - 8.2.4 According to the stability of product quality, transfer can be carried out among normal inspection, relaxed inspection, and tightened inspection in accordance with the transfer rules of GB/T 2828.1. When conducting relaxed inspection, with the general inspection level I and the sample size code letter E, 5 gas springs are sampled according to the relaxed inspection single – sampling plan. When the sample size code letters are D and B, 3 and 2 gas springs are sampled respectively. When conducting tightened inspection, the number of samples is the same as that in 8.2.2.
Technical Specification for Compression Gas Springs (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).