Ring Spring Introduction

I. Scope

This document specifies the definition, classification, design calculation, technical requirements, testing methods, inspection rules, marking, packaging, transportation, and storage of annular springs.

This document applies to annular springs with outer diameters ranging from ϕ18mm to ϕ500mm.

II. Standard Reference Documents

The contents of the following documents are incorporated into this document as indispensable clauses through normative references within the text. For referenced documents with dates, only the version corresponding to that date applies to this document; for referenced documents without dates, the new version (including all amendments) applies to this document.

GB/T 230.1 Rockwell Hardness Test, Part 1: Test Method

GB/T 1031 Surface Roughness Parameters and Their Values

GB/T 1182 Geometric Tolerances - General Principles - Definitions, Symbols, and Representation by Means of Drawing

GB/T 1184-1996 Shape and Position Tolerances, Unspecified Tolerance Values

GB/T 1222 Spring Steel

GB/T 1800.1 Tolerance and Fit - Fundamentals - Part 1: Vocabulary

GB/T 1800.2 Tolerance and Fit Basic Part 2: Basic Regulations for Tolerances, Deviations, and Fits

GB/T 1800.3 Tolerance and Fit - Basic Series - Part 3: Tables of Standard Tolerances and Basic Deviations

GB/T 1800.4 Limits and Fits - Fundamentals - Part 4: Standard tolerance grades and limit deviations for holes and shafts

GB/T 1804-2000 General Tolerance, Tolerance of linear and angular dimensions not specified

GB/T 1805 Spring Terminology

Magnetic Particle Inspection according to GJB 2028

III. Terms and Definitions

Terms and definitions as defined in GB/T 1805 and the following apply to this document.

3.1 Internal (Inside) Ring

Inner ring with external working cone surfaces on both ends

3.2 Outer Ring

Outer ring with internal working cone surfaces on both ends

3.3 End Ring

An inner ring with only one end featuring an outer working cone surface, situated at both ends of a circular spring.

4. Parameter Name, Symbol, and Unit

Table 1's parameter names, symbols, and units apply to this document. For convenience, a structural diagram is provided as shown in Figure 1.

Table 1     Parameter Name, Symbol, and Unit

V. Technical Requirements

5.1 Dimensions

5.1.1 The inner diameter, outer diameter, free height, and compression height of the circular spring should comply with the specifications in the product drawing.

5.1.2 The inner and outer ring dimensions of the annular spring should comply with the relevant provisions of GB/T 1800.1~GB/T 1800.4. The maximum and minimum deviations of dimensions without noted tolerances should conform to the m-grade requirements of GB/T 1804-2000.

5.1.3 The inner and outer rings of the annular spring shall conform to the shape and position tolerances specified in GB/T 1182, GB/T 1184~1996, or the relevant product drawings. Unspecified shape and position tolerances shall comply with the k-class requirements in GB/T 1184-1996.

5.1.4 The radial dimensions and tolerances of the inner and outer rings of the annular spring shall comply with the specifications in Table 2, and the shape of the inner and outer rings is as shown in Figure 2.

Table 2: Radial Dimensions and Tolerances

Table 3: Other Sizes and Tolerances

5.2 Materials

The inner and outer rings of the annular spring should be made of materials conforming to GB/T 1222 and relevant technical agreements, and should be accompanied by a quality certificate of conformity. The material can only be put into use after it has been re-inspected and approved by the manufacturer. The surface of the material should be smooth with no obvious scratches or dents. If other materials are required, they should be agreed upon by both the supplier and the buyer.

5.3 Process

Mass-produced annular springs, with the inner and outer rings made from forged blanks, then rolled into the final shape and size on a transfer ring rolling mill, followed by heat treatment after inspection and qualification.

Ring springs produced in small quantities, with blanks forged freely and then machined to achieve the finished shape and dimensions, followed by heat treatment. Contact surfaces are ground if necessary after heat treatment.

The inner and outer ring surfaces of the annular spring should meet the roughness requirements of GB/T 1031 or the specifications in the product drawing. The roughness of the conical surfaces of the inner and outer rings is generally Ra0.4~Ra0.8.

Due to the thin ring thickness, special attention should be paid during manufacturing to prevent the ring from warping.

5.4 Appearance Quality

The inner and outer ring arcs, cylindrical surfaces, and end faces of the annular spring should be smooth, without any damage, distortion, burrs, or cracks.

5.5 Internal Quality

The inner and outer rings of the circular spring should not have cracks or pores, etc., as internal defects.

5.6 Design and Structure

5.6.1 The design of the circular spring should consider the requirements for stiffness, strength, and motion stability, and should meet the smoothness of motion for the entire cache system and adapt to its working environment.

5.6.2 The structure of the annular spring should meet the basic requirements of not showing stickiness between the inner and outer rings under lubrication conditions.

5.6.3 The annular spring is guided by the inner guide rod. The gap between the annular spring and the guide rod should be left on one side, not exceeding D1 × 2%; the annular spring is guided by the outer guide tube. The gap between the annular spring and the guide tube should be left on one side, not exceeding D2 × 2%.

5.6.4 The typical design characteristic curve OABO of a circular spring within a loading and unloading cycle should be as shown in Figure 3. The OA section indicates that the compression of the circular spring during loading is proportional to the load; the AB section indicates that during the initial stage of unloading, the compression should remain essentially unchanged and exhibit significant hysteresis characteristics; the BO section indicates that when the load decreases to a certain extent, the compression begins to decrease and continues to decrease to zero during the unloading process, at which point the circular spring starts to extend and should return to its original size.

5.6.5 Ring springs should possess well-designed vibration-damping properties, with the total energy loss during deformation and subsequent recovery generally not less than 50%.

5.6.6 Inner and Outer Ring Hardness

The inner and outer rings of the circular spring should generally have a surface hardness value of 48HRC-54HRC after heat treatment.

5.6.7 Surface Treatment

The inner and outer rings of the annular spring should be subjected to anti-corrosion treatment as per relevant standards after mechanical processing, such as phosphatizing or oxidizing.

5.6.8 High-pressure treatment

Circular springs should be subjected to a high-pressure treatment, unless otherwise specified, the general high-pressure treatment time should not be less than 24 hours.

5.6.9　Wear Treatment

Circular springs should be磨合 according to the product drawing specifications. If the drawing does not specify the number of磨合 treatments, the general number of treatments should not be less than 10.

5.6.10 Workload

The ring spring, after being subjected to high-pressure and wear treatment, should meet the specified working load (P1 or P2) as per the product drawings or contract.

5.6.11 Adhesion Rate

The fit rate between the inner and outer rings of the annular spring and the conical contact surfaces should not be less than 75%.

5.6.12 Life span

The service life of the circular spring should comply with the specifications of the product drawings and the manufacturing acceptance technical requirements.

Six: Inspection Rules

6.1 Inspection Conditions

Subject to any other provisions, the following conditions shall apply:

a) Indoor Inspection: Temperature 5℃ ~ 35℃, relative humidity not exceeding 80%.

b) Outdoor Inspection: When using instruments, they should comply with the environmental requirements permitted by the instruments.

6.2 First Article Inspection

6.2.1 The initial identification inspection items for annular springs should be in accordance with the product drawings, contract, and provisions of Table 4.

6.2.2 The inspected samples for the first piece inspection should not be fewer than two.

6.2.3 When all inspected samples and all items in the first article inspection meet the requirements of this specification, the first article inspection is deemed to pass; if any inspected sample or any inspection item in the first article inspection does not meet the requirements of this specification, the first article inspection is deemed to fail.

Table 4: Inspection Items List

6.3 Quality Consistency Inspection

6.3.1 Sampling Plans, Grouping Rules

Circular springs for batch inspection shall consist of inner and outer rings made from the same specification and brand of steel, produced under the same processing conditions. The batch size for inspection shall be as specified in the product drawings or contract.

Group A inspection items follow a full inspection plan, while Group B and C inspection items are executed according to the sampling plan specified in the product drawings or contract.

6.3.2 Qualification Criteria

If all items inspected in Group A meet the requirements of this specification, Group A inspection is deemed合格; if any inspection item in Group A does not meet the requirements of this specification, Group A inspection is deemed不合格.

Articles deemed不合格 in Group A inspection can be re-inspected after repair and non-compliant items should be removed.

If a single-loop part breaks during the high-pressure treatment inspection and the number of broken parts does not exceed 3% of the single-loop part inspection batch, they may be replaced with a high-pressure treated inner or outer ring and re-inspected for high-pressure treatment; if the number of broken single-loop parts exceeds the aforementioned limit, the batch should be re-inspected for high-pressure treatment twice the original time. If another single-loop part breaks during the re-inspection, the batch is deemed不合格 for Group A inspection.

If one sample from Group B inspection does not meet the requirements of this specification, double the quantity should be re-inspected. If another sample still fails to meet the requirements, the batch is deemed不合格 for Group B inspection.

B-group inspection failed batches are subject to full inspection and non-conforming items should be removed.

If any sample in Group C inspection does not meet the requirements of this specification, double the quantity should be re-inspected. If there is still a sample that does not meet the requirements, the batch will be deemed不合格 for Group C inspection.

6.4 Inspection Methods

6.4.1 Dimensions

Inspection should be conducted using universally applicable and interchangeable measuring tools that have been calibrated. The measuring tools for internal or external diameters must have a minimum graduation value of 0.05mm.

6.4.2 Appearance Quality, Surface Treatment

Inspect the appearance quality and surface treatment by visual and tactile methods or by referencing standard samples. In case of disputes, a 5x magnifying glass can be used for examination.

6.4.3 Internal Quality

Inspect in accordance with the provisions of GJB 2028.

6.4.4 Inner and outer ring hardness

Inspected in accordance with GB/T 230.1 standards.

6.4.5 High-pressure treatment

The annular spring is subjected to a high-pressure treatment on a pressure testing machine, compressing it until the coils are in contact with minimal gap, or until the specified height for the corresponding product is reached, or the load specified for the corresponding product is applied, maintaining the required action time for the product. After the high-pressure treatment, the appearance quality is inspected visually.

6.4.6　Break-in Treatment

The磨合 treatment is conducted after the strong pressure treatment has passed inspection.

The annular spring should be kept in a compressed state on the磨合试验机, and it should be operated between H1 and H2, with the number of back-and-forth cycles as specified in 3.9.2. The entire process should not be interrupted and should be completed continuously in one go.

6.4.7 Workload

The measurement of work load should be conducted after the磨合 treatment has been qualified.

On the pressure testing machine, compress the circular spring to H1 or H2, and measure and record the working load P1 or P2.

When the work load does not conform to the product drawings or contract specifications, adjustable washers can be used for adjustment. The thickness and number of the washers should comply with the requirements specified in the product technical standards.

6.4.8 Tolerance Rate

Tested using the coal smoke method.

6.4.9 Life span

Conduct fatigue tests on the annular springs, ensuring the stroke corresponds to the actual working stroke, the reciprocating frequency matches the working frequency, and the number of runs is not less than 110% to 130% of the actual working life cycles. After the fatigue test, inspect or check the working load, internal quality, and appearance quality of the annular spring to ensure they meet the requirements of the product drawings and this specification, and record the findings.

7. Branding, Packaging, Transportation, and Storage

7.1 Branding

7.1.1 There should be a clear durability mark at a prominent location on the circular spring.

7.1.2 The logo should include the following contents:

a) Product Model

b) Product Trademark

c) Manufacturer's name or code;

d) Manufacturing Date (Year, Month).

7.1.3 Products that pass the factory inspection should have a certificate of compliance or a compliance mark.

7.1.4 Certificate of Conformity includes: (1) Product name, model, specification; (2) Product number; (3) Manufacturer's name or code; (4) Manufacturing year, month; (5) Inspector.

7.2 Packaging

7.2.1 The product's packaging and storage labels should meet the customer's requirements.

7.2.2 The packaging should ensure that it is not deformed under pressure.

7.2.3 The packaging box should have product name, quantity, and protective identification.

7.2.4 The packaging box should indicate the stacking direction and the number of layers allowed for stacking.

7.2.5 The packaging box should include a product certification and a product manual.

7.3 Transportation and Storage

7.3.1 The packaging box of the annular spring should be kept upright during transportation and storage, and should not be placed horizontally. There should be no damage to the packaging.

7.3.2 During transportation and storage, ring springs should be avoided from impacts, and they should be kept away from contact with acids, alkalis, salts, oils, water, ash, and other organic solvents. They should also be as far away from heat sources as possible.

A.1 Common Ring Spring Size Series is listed in Table A.1

Table A.1

B.1 Selection of Ring Spring Design Parameters

(1) The cone surface angle β: When the cone surface angle β is selected to be smaller, the spring stiffness is lower. If β < ρ, self-locking occurs during unloading, meaning it cannot rebound. If β is selected too large, the load PR during the recovery of elastic deformation is greater, which reduces the shock-absorbing capability of the annular spring. During design, β can be taken as 12° to 20°; when the precision of the cone surface processing is high, β can be 12°; when the processing precision is average, β is often 14.04°; and when the lubrication conditions are poor and the friction coefficient is high, β should be larger to avoid self-locking.

(2) The friction coefficient fμ and the friction angle ρ can be selected under the following conditions:

(3) Allowable stress for annular springs is as shown in Table B.1.

Table B.1 Allowable Stress of Common Materials for Ring Springs / MPa