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.

Section II: Standard Reference Documents

The contents of the following documents are incorporated as essential terms of this document by normative references within the text. For referenced documents with a dated notation, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest 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 Shape and Position Tolerances General Principles Definitions, Symbols, and Representation of Drawing Notation

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

GB/T 1222 Spring Steel

GB/T 1800.1 Limits and Fits Basic Part 1: Vocabulary

GB/T 1800.2 Tolerance and Fit Basic Part 2: Basic Rules of Tolerances, Deviations, and Fits

GB/T 1800.3 Tolerance and Fit - Basic Series, Part 3: Standard Tolerance and Basic Deviation Tables

GB/T 1800.4 Tolerance and Fit Basic Part 4: Standard Tolerance Grades and Limits of Fit 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 at 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 convenience, 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 in the product drawing.

5.1.2 The inner and outer ring dimensions of the annular spring shall comply with the relevant provisions of GB/T 1800.1~GB/T 1800.4. The maximum and minimum deviations of dimensions without noted tolerances shall conform to the m-class specification in 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-grade requirements in 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 certification. The material may only be put into use after it has been re-inspected and approved by the manufacturer. The material surface should be smooth with no visible scratches or dents. For other materials, the selection should be agreed upon by both parties.

5.3 Process

High-volume produced circular springs, with the inner and outer rings made from forged blanks, then rolled into finished shape and size using a transfer ring mill, followed by heat treatment after inspection for quality.

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, with the roughness of the conical surfaces of the inner and outer rings generally being 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, deformation, burrs, or fractures.

5.5 Internal Quality

The inner and outer rings of the annular spring should not have cracks and blow holes, or other 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, ensuring it meets the smoothness of motion of the entire cache system and adapts 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 annular spring is guided by the inner guide rod, and the gap between the annular spring and the guide rod should be left with a single side not exceeding D1 × 2%; the annular spring is guided by the outer guide tube, and the gap between the annular 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 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 a significant hysteresis characteristic; 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 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 annular 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 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

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

5.6.10 Workload

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

5.6.11 Tensile Elongation

The fit rate between the inner and outer rings of the circular 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

Except as otherwise specified, the following conditions shall apply:

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

b) Outdoor Inspection: When using equipment, it must meet the environmental requirements permitted by the equipment.

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 specifications in Table 4.

6.2.2 The inspected samples for the first article inspection should not be less than two pieces.

6.2.3 If all inspected samples and items in the initial inspection meet the requirements of this specification, the initial inspection is deemed to pass; if any inspected sample or inspection item in the initial inspection does not meet the requirements of this specification, the initial 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 should consist of inner and outer rings made from the same specification and brand of steel, produced under the same processing conditions. The batch size of the inspection batch shall be as specified by the product drawing or contract.

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　Criteria for Conformity

If all items in Group A inspection meet the requirements of this specification, Group A inspection is deemed to pass; if any inspection item in Group A does not meet the requirements of this specification, Group A inspection is deemed to fail.

Disqualified items from Group A inspection can be re-inspected after repair and should be removed from the batch.

If a single ring part breaks during the high-pressure treatment inspection and the number does not exceed 3% of the inspected batch of single ring parts, it may be replaced with a high-pressure treated inner or outer ring and re-inspected; if the number of broken single ring parts exceeds the above limit, the batch should be re-inspected with double the time. If another single ring part breaks during the re-inspection, the batch is deemed to fail the A-group inspection.

If one sample from Group B 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 for Group B inspection.

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

If any sample in Group C 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 Group C inspection.

6.4 Inspection Methods

6.4.1 Size

Inspection using general or interchangeable measuring tools that have been calibrated and verified; the measuring tools for inner or outer diameter should have a minimum graduation value of 0.05mm.

6.4.2 Appearance Quality, Surface Treatment

Inspect the appearance quality and surface treatment by visual inspection, tactile feel, or reference to standard samples. A 5x magnifying glass can be used for inspection in case of disputes.

6.4.3 Internal Quality

Inspection conducted in accordance with the provisions of GJB 2028.

6.4.4 Inner and outer ring hardness

Inspect according to the GB/T 230.1 specifications.

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 touch without significant gaps, or to the specified height for the corresponding product, or to the load specified for the corresponding product, while maintaining the specified duration of action. After the high-pressure treatment, the appearance quality is inspected visually.

6.4.6 Lubrication and磨合处理

The磨合processing is conducted after the strong pressure processing is qualified.

On the磨合试验机, keep the annular spring in a compressed state and operate it back and forth between H1 and H2, as specified in 3.9.2. The entire process should not be interrupted and should be completed in one continuous operation.

6.4.7 Workload

The measurement of workload should be conducted after the磨合 treatment is qualified.

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

If 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 provisions of the product technical requirements.

6.4.8 Adhesion Rate

Tested using the coal smoke method.

6.4.9 Life Span

Conduct fatigue tests on the annular spring, ensuring the stroke aligns with the actual working stroke, the reciprocation frequency matches the working frequency, and the operating cycles are no fewer 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 relevant 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 legibly placed in a prominent position 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 passing the factory inspection should have a certificate of compliance or a compliance 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 transportation labels should meet the customer's requirements.

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

7.2.3 The packaging box should have labels indicating the product name, quantity, and protective measures.

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

7.2.5 The packaging box should be accompanied by a product certification and a product manual.

7.3 Transportation and Storage

7.3.1 During transportation and storage, the packaging box of the annular spring should be kept upright, not lying flat, and there should be no damage to the packaging.

7.3.2 Circular springs should be handled with care to avoid impacts during transportation and storage. They should be kept away from acids, alkalis, salts, oils, water, soot, and other organic solvents. It is recommended to maintain a safe distance from heat sources.

Section A.1 lists the standard series of circular spring dimensions in Table A.1.

Table A.1

B.1 Ring Spring Design Parameters Selection

(1) Conical Surface Angle: When the conical surface angle 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 greater, which reduces the shock-absorbing capacity of the annular spring. During design, β can be selected between 12° to 20°. When the conical surface machining accuracy is high, β can be 12°; when the machining accuracy is average, β is often 14.04°. In poor lubrication conditions with a higher friction coefficient, β should be larger to prevent self-locking.

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

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

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