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1、BRITISH STANDARD BS 1726-3:2002 Cylindrical helical springs made from round wire and bar Guide to methods of specifying, tolerances and testing Part 3: Torsion springs ICS 21.160 - BS 1726-3:2002 This British Standard, having been prepared under the direction of the Engineering Sector Policy and Str
2、ategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 25 September 2002 BSI 25 September 2002 The following BSI references relate to the work on this British Standard: Committee reference GME/15 Draft for comment 02/702406 DC ISBN 0 580 39721 1 Committe
3、es responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee GME/15, Mechanical springs, upon which the following bodies were represented: British Impact Treatment Association Institute of Spring Technology Amendments issued since publication
4、 Amd. No.DateComments - BS 1726-3:2002 BSI 25 September 2002 i Contents Page Committees responsible Inside front cover Forewordii 1Scope1 2Normative references1 3Terms, definitions and symbols1 4Specifying springs for general purposes2 5Tolerances11 6Methods of testing14 Figure 1 Data sheet 13 Figur
5、e 2 Form of legs4 Figure 3 Direction of coiling5 Figure 4 Conventions for describing relative leg orientation6 Figure 5 Data sheet 29 Figure 6 Example torque testing layout11 Table 1 Calculated free relative leg orientation tolerance ( degrees)12 - BS 1726-3:2002 ii BSI 25 September 2002 Foreword BS
6、 1726-3 was first published in 1951 and revised in 1964 to incorporate much of the essential information from ADE Design Data Sheets, which were no longer available from HM Stationery Office and for which copyright permission to republish was obtained. The standard was revised in 1987 take account o
7、f current manufacturing processes. BS EN 13906-3 was published in 2001 and under the rules of CEN the UK is obliged to withdraw conflicting standards. This edition of BS 1726-3 includes those provisions of the previous edition not included in the EN standard. Together with BS 8726-2:2002 and BS EN 1
8、3906-3:2001, this edition of BS 1726-3 supersedes BS 1726-3:1988, which is withdrawn. BS 1726 is published in three parts: Part 1: Compression springs; Part 2: Extension springs; Part 3: Torsion springs. BS 8726-2:2002 contains the provisions for design of compression springs made from square and re
9、ctangular material previously contained in BS 1726-3. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal
10、obligations. Summary of pages This document consists of a front cover, an inside front cover, pages i and ii, pages 1 to 15 and a back cover. The BSI copyright displayed in this document indicates when the document was last issued. - BS 1726-3:2002 BSI 25 September 2002 1 1 Scope This Part of BS 172
11、6 provides guidance on the specification, tolerancing and testing of parallel sided helical torsion springs manufactured from round wire and bar. It applies to springs which may or may not be stress relieved after forming (hereinafter referred to as group A springs) and to springs the material of wh
12、ich has undergone a structural change by heat treatment after forming (hereinafter referred to as group B springs). This standard gives two methods of specifying springs for general purposes and one method of testing springs. NOTEIt is not recommended that torsion springs be loaded in the opposite d
13、irection to that of coiling. If this is necessary then discussions should take place between purchaser and supplier. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this British Standard. For dated references
14、, subsequent amendments to, or revisions of, any of these publications do not apply. For undated references, the latest edition of the publication referred to applies. BS 887, Specification for precision vernier callipers. BS 969, Specification for limits and tolerances on plain limit gauges. BS EN
15、ISO 7500-1, Tension/compression testing machines Verification and calibration of the force measuring system. BS 1726-1, Cylindrical helical springs made from round wire and bar Guide to methods of specifying, tolerances and testing Part 1: Compression springs. BS EN 13906-3, Cylindrical helical spri
16、ngs made from round wire and bar Calculation and design Part 3: Torsion springs. 3 Terms, definitions and symbols 3.1 Terms and definitions For the purposes of this Part of BS 1726 the definitions given in BS 1726-1 apply. 3.2 Symbols SymbolTermUnit cspring indexmm Dmean coil diametermm Dchange in m
17、ean coil diametermm Dooutside diametermm Dtol.mean coil diameter tolerancemm dmaterial diameter mm dmax.maximum diameter of circular section material allowing for material size tolerance Hz etolerance on size of material cross-sectionmm Emodulus of elasticity N/mm2 FTtolerance factor for torque Kost
18、ress correction factor for circular section wire lcombined effective length of legsmm Lofree body length of springmm Lo, tol.tolerance on free body lengthmm Ltloaded body length of springmm mshape factormm - BS 1726-3:2002 2 BSI 25 September 2002 4 Specifying springs for general purposes 4.1 General
19、 There are two methods by which a customer may specify a spring. In the first method the customer presents the supplier with a complete design and indicates what manufacturing processes, such as stress relieving, prestressing and shot peening, should be carried out. In this case the information shou
20、ld be supplied on Data Sheet 1 (Figure 1). When the customer does not have the information to complete Data Sheet 1, the customer should complete Data Sheet 2 (Figure 5). This is an application for a spring design in which the customer should specify the requirements from an operational point of vie
21、w, giving such information as dimensional constraints, forcelength parameters, fatigue life, resistance to corrosion, in order that the supplier can produce a spring design to meet these requirements. When the spring supplier has prepared a design from the information on Data Sheet 2, the supplier w
22、ill complete Data Sheet 1 and submit it to the customer for approval. 4.2 Method one (customer design) 4.2.1 Use of Data Sheet 1 Details of the required spring should be supplied on Data Sheet 1 (Figure 1) using standard nomenclature. Only the essential dimensions and properties, for which the sprin
23、g is to be inspected, should be toleranced, although other features may be included for information. nnumber of active coils in spring nchange in number of active coils during loading Ntotal number of coils in spring ppitchmm Rmin.minimum allowable inside radius of any bendmm Snominal torsional rate
24、N mm/degree tthickness of any surface coatingmm Ttorque at any angleN mm Ttol.tolerance on torqueN mm Tchange in torqueN mm relative leg orientation under torquedegrees o relative leg orientation in free statedegrees tol. tolerance on relative leg orientationdegrees angular rotation of springdegrees
25、 Bending stress in spring N/mm2 SymbolTermUnit - BS 1726-3:2002 BSI 25 September 2002 3 SPECIFICATION FOR HELICAL TORSION SPRINGS BS 1726-3:2002DATA SHEET 1 Part Serial No. This form should be completed with reference to BS 1726-3:2002 Clause 4.2 Torque test layout if required5Thermal treatment (a)S
26、tress relieving (group A) NoYes If yes Time minTemperatureC (b)Heat treatment and hardness (group B) 6Maximum deflection Maximum deflectionRevdegree 7Dimensional tolerances Outside diameter, mm Free body length, mm Leg length: 1 mm2 mm Free relative leg orientation, mm 1Material8To be completed only
27、 if torque testing is a requirement Specification No. 8.1Rate Diameter mm SN mm/degree; 2Direction of coiling8.2Torque Right Hand Left Hand at Test position 1 (TP1) N mm at Test position 2 (TP2) N mm 3Form and length of legs8.3Property tolerances (Select only 2) Leg 1Leg 2 Rate, N mm/degree Axial Fr
28、ee relative leg orientation, degree Tangential Torque at TP1 N mm Radial Over-centre Torque at TP2 N mm Radial Over-centre9 Surface coating Lengths mm mm10 Identification 4Nominal dimensions11Special requirements Outside diameter Do mm Mandrel diameter (max.) mm Free body length, Lo mm Number of coi
29、ls, N Free relative leg orientation, o mm Sheet 1 of Serial/design/Part No. Figure 1 Data sheet 1 - BS 1726-3:2002 4 BSI 25 September 2002 A detailed drawing is not necessary where the required spring conforms to the standard types, as shown in Figure 2. Only for those springs that require special l
30、eg geometry is a detailed drawing necessary. Figure 2 Form of legs - BS 1726-3:2002 BSI 25 September 2002 5 Before completing Data Sheet 1, the designer should determine whether torque testing is a requirement. This decision affects tolerances for certain parameters (see 5.2 and 5.3), which boxes ar
31、e to be completed, and the need or otherwise for a torque testing layout. If torque testing is a requirement then a test layout should be presented either on, or as a supplement to, Data Sheet 1. Complete the data sheet in accordance with 4.2.9.1. The designer should be fully aware of the aforementi
32、oned guidelines and comply with the following. a) Specify only those particulars which are of functional importance by marking the appropriate squares and/or by entering the relevant values in each box. NOTEBox 8 is only to be completed if torque testing is required. b) Avoid redundant dimensioning.
33、 c) Refer to BS EN 13906-3 for the methods of calculation used to determine values for rate, torque, stress, etc. d) If space is insufficient in any box, details should be entered on a supplementary sheet and attention drawn to this fact in the appropriate box. 4.2.2 Material Complete box 1, by givi
34、ng the material type and specification code quoting the relevant British Standard wherever possible. In cases where torsion springs are produced from annealed material or are manufactured by a hot coiling method, they may require subsequent heat treatment (group B). If this is the case, specify the
35、final hardness required and the process to be used, e.g. austemper, harden and temper. 4.2.3 Direction of coiling The action of the spring is dependent on the direction of coiling. Enter the direction of coiling in box 2. Figure 3 shows the convention for defining direction of coiling. 4.2.4 Form an
36、d lengths of legs Where the legs are of a standard form (see Figure 4), indicate the form in box 3 together with the appropriate lengths. Alternatively, provide a detailed drawing on Data Sheet 1 or attach a supplementary drawing sheet. A fully dimensional drawing showing clearly the shape of the le
37、gs with their relationship to the body should be provided and attached to Data Sheet 1 or 2. In view of the wide variety of leg forms it is impractical to give tolerances for these dimensions in this standard, but some guidelines are suggested in Clause 6. Figure 3 Direction of coiling - BS 1726-3:2
38、002 6 BSI 25 September 2002 4.2.5 Nominal dimensions The dimensions to be entered in box 4 are for information only unless a corresponding tolerance is to be applied in box 7 and, in the case of relative leg orientation when torque testing is required, when entries should be made in box 8. 4.2.5.1 O
39、utside diameter, Do Enter the outside diameter of the coil. 4.2.5.2 Mandrel diameter Enter the maximum diameter over which the spring is to operate. This is also the size of mandrel that will be used for testing the spring if torque testing is a requirement. Due allowance should be made for a reduct
40、ion in inside diameter during loading. 4.2.5.3 Free body length, Lo Enter the free body length. Group B springs cannot generally be produced with completely closed coils and account of this should be taken when stating free body length. 4.2.5.4 Number of coils, N Only enter the number of full coils.
41、 NOTEA fully dimensioned drawing showing clearly the shape of the legs with their relationship to the body should be provided and attached to data sheet 1 or 2. In view of the wide variety of leg forms it is impractical to give tolerances for these dimensions in this standard, but some guidelines ar
42、e suggested in Clause 5 Figure 4 Conventions for describing relative leg orientation - BS 1726-3:2002 BSI 25 September 2002 7 4.2.5.5 Relative leg orientation, o The convention for the description of relative leg orientation is directly related to the number of part coils in the spring. Examples of
43、this are shown in Figure 4. 4.2.6 Thermal treatment 4.2.6.1 If stress relieving is required for group A springs, the duration and temperature should be given in box 5(a). 4.2.6.2 Heat treatment and hardness requirements for group B springs should be given in box 5(b). 4.2.7 Maximum deflection Indica
44、te in box 6 the maximum elastic deflection, in revolutions and degrees, through which the legs have to move relative to each other. A degree of prestressing is automatically present in a cold coiled torsion spring as a result of winding the coils. Consequently, it is rarely necessary to carry out a
45、secondary prestressing operation. Springs that are hot coiled or hardened and tempered after coiling do not contain an element of prestress. If prestressing is required this should be stated in box 11. 4.2.8 Dimensional tolerances The tolerances to be entered in box 7 will depend on whether torque t
46、esting is a requirement. 4.2.8.1 Outside diameter Refer to either 5.2.2 or 5.3.1 for the appropriate tolerance. 4.2.8.2 Free body length Refer to 5.2.3 for tolerance on free body length. This tolerance is only to be stated if torque testing is not required. 4.2.8.3 Leg length Refer to 5.4.4 for leg
47、length tolerances. 4.2.8.4 Relative leg orientation Refer to 5.2.4 or 5.3.3 for the relative leg orientation tolerance. This is only to be entered if torque testing is not required. 4.2.9 Properties 4.2.9.1 Torque testing Only complete box 8 if torque testing is required. However, to avoid over-dimensioning the spring it is necessary to be aware that no more than two parameters are needed to define torque performance. In addition to the details in box 8 a torque testing layout should also be prov