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 an outer diameter ranging from Φ18mm to Φ500mm.

II. Normative References

The contents of the following documents are incorporated as indispensable clauses of this document by the normative references within. For dated references, only the version corresponding to that date applies to this document; for undated references, the new version (including all amendments) applies to this document.

GB/T 230.1 Metal Rockwell Test Part 1: Test Method

GB/T 1031 Surface Roughness Parameters and Their Values

GB/T 1182 Geometric Tolerance Shapes and Positional Tolerances General Rules Definitions, Symbols, and Methods of Representation

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

GB/T 1222 Spring Steel

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

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

GB/T 1800.3 Limits and Fits Basic Part 3: Tables of Standard Tolerances and Basic Deviations

GB/T 1800.4 Tolerance and Fit Basic Part 4: Standard Tolerance Grades and Limit Deviations for Holes and Shafts

GB/T 1804-2000 General Tolerance, Tolerance for Linear and Angular Dimensions Not Specified

GB/T 1805 Spring Terminology

Magnetic Particle Inspection (MPI) per GJB 2028

III. Terms and Definitions

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

3.1 Inner Ring

Inner ring with external working cone surfaces at 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 external working cone surface, located at the ends of a circular spring.

4. Parameter Name, Symbol, and Unit

Table 1's parameter names, symbols, and units apply to this document. For ease of use, a structural illustration 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 compressed height of the annular spring should comply with the specifications of the product drawing.

5.1.2 The inner and outer ring dimensions of the annular spring should conform to the relevant provisions of GB/T 1800.1~GB/T 1800.4. The extreme deviation of dimensions without noted tolerance should comply with the m-class provisions in GB/T 1804-2000.

5.1.3 The inner and outer ring shapes and positional tolerances of the annular spring should comply with the relevant provisions of GB/T 1182, GB/T 1184-1996, or the product drawings. Where the shape and positional tolerances are not specified, they should conform to the k-grade provisions of GB/T 1184-1996.

5.1.4 The radial dimensions and tolerances of the inner and outer rings of the annular spring should 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 materials used for the inner and outer rings of the annular spring should comply with the provisions of GB/T 1222 and relevant technical agreements, and should be accompanied by a quality certificate. The material should be smooth with no visible scratches or dents. In case of the need for other materials, the decision should be made by both the supplier and the buyer.

5.3 Process

Large-scale production of annular springs, with the blanks of the inner and outer rings forged, then rolled into the finished shape and size on a transfer ring mill, followed by heat treatment after inspection and approval.

Small-batch ring springs, with blanks forged freely and then machined to achieve finished shape and size, followed by heat treatment. Contact surfaces are ground if necessary after heat treatment.

The inner and outer rings of the annular spring should meet the surface roughness requirements of GB/T 1031 or the relevant provisions in the product drawing. The surface 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 becoming distorted.

5.4 Appearance Quality

The inner and outer rings of the annular spring should be smooth with no damage, distortion, burrs, or fractures.

5.5 Internal Quality

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

5.6 Design and Structure

5.6.1 The design of the annular 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 that there is no sticking phenomenon between the inner and outer rings under lubrication conditions.

5.6.3 The circular spring is guided by the inner guide rod. The gap between the circular spring and the guide rod should be left with a single side not exceeding D1 × 2%; the circular spring is guided by the outer guide tube. The gap between the circular spring and the guide tube should be left with a single side not exceeding D2 × 2%.

5.6.4 The typical design characteristic curve OABO of the annular spring within a loading and unloading cycle should be as shown in Figure 3. The OA section indicates that the compression of the annular spring during loading is proportional to the load; the AB section indicates that the compression should remain essentially unchanged and exhibit a significant hysteresis characteristic during the initial unloading stage; the BO section indicates that as 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 annular spring starts to extend and should return to its original size.

5.6.5 The annular spring should possess well-designed vibration-damping properties, with the total energy loss upon 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, after heat treatment, should generally have a surface hardness value of 48HRC-54HRC.

5.6.7 Surface Treatment

The inner and outer rings of the circular spring should be subjected to anti-rust treatment in accordance with relevant standards after mechanical processing, such as phosphatizing and oxidizing.

5.6.8 High-pressure Treatment

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

5.6.9　Break-in Treatment

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

5.6.10 Workload

The ring spring, after being subjected to high-pressure and磨合 processing, 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, corresponding to 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 technical requirements for manufacturing acceptance.

Section 6: Inspection Regulations

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 must comply with the environmental requirements permitted by the instruments.

6.2 First Article Inspection

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

6.2.2 The inspected samples for the first article inspection should be at least two in number.

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 be合格. 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 be不合格.

Table 4: Inspection Items List

6.3 Quality Consistency Inspection

6.3.1 Sampling Plans, Grouping Rules

Circular springs for batch inspection should consist of inner and outer rings made from the same specification and brand of steel, produced under the same process conditions. The batch size for inspection should be as per the product drawings or contract specifications.

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

6.3.2　Qualified 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.

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

If a single ring part breaks during the high-pressure treatment inspection and the number does not exceed 3% of the single ring parts in the inspection batch, it is permissible to replace it with a high-pressure treated inner or outer ring and then re-inspect it under high-pressure treatment. If the number of broken single ring parts exceeds the aforementioned limit, the batch should be re-inspected under high-pressure treatment twice the original time. If another single ring part breaks during the re-inspection, the batch is deemed不合格 in Group A inspection.

If one sample in the B group inspection does not meet the requirements of this specification, double the number should be re-inspected. If another sample still does not meet the requirements, the batch will be deemed不合格 in the B group inspection.

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

If any sample in the C-group inspection does not meet the requirements of this specification, double the number of samples should be re-inspected. If another sample still fails to meet the requirements, the batch will be deemed不合格 in the C-group inspection.

6.4 Inspection Methods

6.4.1 Dimensions

Inspection using general or interchangeable measuring tools that have been calibrated, with the measuring tools for inner or outer diameter having 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 examination or by referencing the standard sample. In case of disputes, a 5X magnifying glass can be used for inspection.

6.4.3 Internal Quality

Inspected in accordance with GJB 2028 specifications.

6.4.4 Inner and Outer Ring Hardness

Inspected in accordance with GB/T 230.1 specifications.

6.4.5 High-pressure Treatment

The annular spring is subjected to high-pressure treatment on a pressure testing machine, compressing it until the coils are in contact with no significant gaps, or until it reaches the specified height for the corresponding product, or until the specified load 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 Wear-in Treatment

The磨合treatment is conducted after the strong pressure treatment passes inspection.

On the磨合试验机, keep the annular spring in a compressed state and operate it between H1 and H2 as per the specifications 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 annular 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 drawing 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 Tensile Ratio

Tested by coal smoke method.

6.4.9 Life Span

Conduct fatigue tests on the circular springs, ensuring the stroke matches the actual working stroke, the reciprocating frequency is the same as the working frequency, and the operating times should not be 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 circular spring to ensure they meet the requirements of the corresponding product drawings and this specification, and record the findings.

Section 7: Branding, Packaging, Transportation, and Storage

7.1 Brand

7.1.1 A clear durability mark should be present in a prominent location on the circular spring.

7.1.2 The logo should include the following:

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 conformity or a conformity mark.

7.1.4 Certificate of Conformity includes: (1) Product name, model, specifications; (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 surface should have product name, quantity, and protective markings.

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 the product certificate of conformity and the product manual.

7.3 Transportation and Storage

7.3.1 Ring springs should be packed in an upright position during transportation and storage, with no damage to the packaging visible.

7.3.2 Ring springs should be handled to avoid impacts during transportation and storage. They should be kept away from acids, alkalis, salts, oils, water, ash, and other organic solvents. It is advisable to maintain a distance from heat sources.

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

Table A.1

B.1 Selection of Ring Spring Design Parameters

(1) Cone Surface Inclination: When the cone surface inclination β is chosen to be smaller, the spring stiffness is lower. If β < ρ, self-locking will occur during unloading, meaning it cannot return to its original position. If β is chosen too large, the load PR during elastic deformation recovery is higher, reducing the shock-absorbing capacity of the annular spring. During design, β can be selected between 12° to 20°. When the cone surface machining accuracy is high, β can be 12°; when the machining accuracy is average, β is often 14.04°; and when lubrication conditions are poor and the friction coefficient is high, β should be larger to prevent self-locking.

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

(3) The allowable stress for the circular springs is as shown in Table B.1.

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