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इंटरनेट मानक Disclosure to Promote the Right To Information Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. “जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ” Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru “The Right to Information, The Right to Live” “Step Out From the Old to the New” IS 2458 (2001): Vocabulary of Gear Terms - Definitions Related to Geometry [PGD 30: Transmission Devices] “!ान $ एक न’ भारत का +नम-ण” Satyanarayan Gangaram Pitroda ““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee”” “!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै” Bhartṛhari—Nītiśatakam “Knowledge is such a treasure which cannot be stolen” ~pD IS 2458:2001 ISO 1122-1:1998 ( ~y7awT) Wa7 Indian Standard VOCABULARY OF GEAR TERMS — DEFINITIONS RELATED TO GEOMETRY ( First Revision) ICS 21.200; 01.040.2 @ BIS 2001 BUREAU OF INDIAN STAN DARDSO MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DE LHI 110002 December 2001 Price Group 11 ) Gears Sectional Committee, BP 13 NATIONAL FOREWORD This Indian Standard ( First Revision ) which is identical with ISO 1122-1 :1998 ‘Vocabulary of gear terms — Part 1: Definitions related to geometry’ issued bythe International Organization for Standardization ( ISO )was adopted by the Bureau of Indian Standards on the recommendation of the Gears Sectional Committee and approval of the Basic and Production Engineering Division Council. This standard was originally published in 1965. This revision of the standard has been made by adoption of ISO 1122-1 : 1998 under dual numbering system. This standard covers the Vocabulary of Gears which devoted solely to geometrical definitions including Bevel and Hypoid Gears, The Bevel and Hypoid Gears were earlier covered in IS 2458 ( Part 2 ) :1984 ‘Glossary of terms for toothed gearing: Part 2 Bevel and hypoid gears’. As such IS 2458 ( Part 2 ) :1984 now merged with this revision and stands withdrawn after publication of this standard. The text of ISO Standard has been approved as suitable for publication as an Indian Standard without deviations. Inthe adopted standard, certain conventions are not identical to those used in Indian Standard. Attention is especially drawn to the following: a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’. b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a full point (.) as the decimal marker. Technical Corrigendum 1to the above International Standard has been incorporated. Only the English language text in the International Standard has been retained while adopting it in this Indian Standard. “. IS 2458:2001 j ISO 1122-1:1998 ‘; ,:} Indian Standard 4 1 VOCABULARY OF GEAR TERMS — DEFINITIONS RELATED TO GEOMETRY ( First Revision) Scope 1.1.1.3 train of gears This part of ISO 1122 concerns the part of the international vocabulary of gears which isdevoted any combination of gear pairs solely to geometrical definitions. Itgives, for each ofthe geometrical terms relative to gears, a standard definition which will be valid internationally, the corresponding term in each language being chosen as far as possible insuch a way as to directly reflect the meaning of the definition. NOTE — Since the choice of corresponding terms can only bepartially fulfilled inany particular language, due to thenecessity ofrespecting certain established conventions, itisadvisable, asfarastranslation intoother languages is concerned, torefer always tothe meaning ofthe definition 1.1.1.4 itself,ratherthantoasimpletransposition oftheoriginalterm. parallel gears 1 General definitions gear pair whose axes are parallel 1.1 Kinematic definitions 1.1.1 Relative position of axis 1.1.1.1 . toothed gear toothed member designed to transmit motion to, or receive motion from, another toothed member, -/ by means of successively en gaging teeth 1.1.1.5 bevel gears gear pair whose axes intersect ‘\ \ \ 1.1.1.2 gear pair ,/ A : mechanism consisting of two gears rotatable around axes relative positions of which are fixed % and one gear turns the other by the action of 1.1.1.6 teeth successively in contact crossed gears gear pair having skewed axes !/” —.— . . @ 1’ 1 ./=i-\ IS 2458:2001 ISO 1122-1:1998 1.1.1.7 centre distance o shortest distance between the axes of a gear pair —. -c “–”+”–”} “\ ~ /’ \ + /“ 1 1.1.1.8 shaft angle smallest angle through which one of the axes must be rotated in order to bring the axes into coincidence (bevel gear pair), or must beswivelled so that the axes are parallel ( crossed gear pair )and their directions of rotation are opposite 1.1.2 Mating gears 1.1.1.9 epicyclic gear 1.1.2.1 epicyclic gear train mating gears planetary gear planetary gear train either one of the two gears of a pair, considered in relation to the other combination of coaxial elements, of which one or more are annulus gears ( 1.1.2.8 )and one or 1.1.2.2 more are planet carriers ( 1.1.2.10 ) which turn pinion around the common axes and support one or that gear of a pair which has the smaller number more planet gears ( 1.1.2.9 ) which mesh with of teeth the annulus gears and one or more sun gears (1.1.2.7) 1.1.2.3 wheel ,,. gear that gear of a pair, which has the larger number A; Sun gear of teeth B: Annulus gear NOTE —Wheel or gear isasimplification of“conjugate D c: Planet gear(s) gear wheel of pinion”, when the term is clearly used in opposition to“pinion”, D: Planet carriers 1.1.2.4 driving gear that gear of a pair which turns the other 2 IS 2458:2001 ISO 1122-1:1998 1.1.2.5 gear divided by the angular speed of last driven driven gear gear of a gear train that gear of a pair which is turned by the other NOTE —When necessary, aplus sign should be added tothe transmission ratio when the rotation directions are 1.1.2.6 thesame andaminus sign added when they areopposite. idler gear with external teeth 1.1.3.3 gear that meshes with two other gears and which speed reducing gears is driven by one and drives the other pair or train of gears, ofwhich the angular velocity 1.1.2.7 of the last driven gear is less than that of the sun gear with external teeth first driving gear ( epicyclic train ) innermost gear with external 1.1.3.4 teeth speed increasing gears 1.1.2.8 pair or train of gears, of which the angular velocity annulus gear of the last driven gear is greater than that of the first driving gear ( epicyclic train ) outermost gear with internal teeth 1.1.3.5 1.1.2.9 speed reducing ratio planet gear transmission ratio of speed reducing gears (epicyclic train) one of the idler gears mounted in a planet carrier 1.1.3.6 speed increasing ratio 1.1.2.10 planet carrier inverse ofthe transmission ratio of speed reducing gears (epicyclic train) coaxial member which supports one or more planet gears 1.1.4Pitch and reference surfaces n 1.1.2.11 1.1.4.1 gear segment pitch surface gear with teeth covering less then 360° in a given gear pair, the geometrical surface described by the instantaneous axis of relative 1.1.2.12 movement of the mating gear, in relation to the number of teeth gear under consideration number of the full complement of teeth of a gear NOTE — The pitch surfaces of parallel and bevel gear pairs roll together without slip. Pitch surfaces ofcrossed 1.1.2.13 ( cylindrical and hypoid ) gear pairs have a sliding sector of a gear component along their tooth flanks. part of a gear with teeth 1.1.4.2 reference surface 1.1.3 Relative speeds imaginary conventional surface relative to which 1,1.3.1 the dimensions of the teeth of a gear are defined gear ratio quotient of the number of teeth of the wheel divided &’”’” by the number of teeth of the pinion 1.1.3.2 transmission ratio quotient of the angular speed of the first driving 3 IS 2458:2001 ISO 1122-1:1998 1.1.4.3 1.2.1.6 reference ...........’) diametral pitch qualification applicable to terms defined in relation quotient of n divided by the pitch at the reference to the reference surface of a gear surface, expressed in inches 1.1.4.4 1.2.1.7 1) operating ........... unity value of dimension qualification applicable to terms defined in relation quotient of the dimension under consideration, to the pitch surface of a gear expressed in millimetres, divided by the module 1.1.4.5 NOTE —When the dimension under consideration isthe profile shift, the value iscalled “coefficient”. pitch plane 1.2.1.8 pitch surface of a rack or crown wheel, also any effective facewidth plane tangent to the pitch surface of an individual gear that part of the facewidth deemed to be bearing NOTE—The pitch plane ofagear pair isatangent plane load through the line or, point of contact between their pitch surfaces, 1.2.2 Tip and root surfaces 1.2 Tooth characteristics 1.2.2.1 tip surface 1.2.1 Dimensions and coefficients coaxial surface of revolution bounding the outer 1.2.1.1 extremities of external gear teeth or the inner gear tooth extremities of internal gear teeth each of those elements of a gear which enter ,,—. 1.221 —....,, spaces between the corresponding elements of a mating gear and which, by virtue of their shape, ensure that one gear turns the other m ‘m” 1.2.1.2 = tooth space space between two adjacent teeth of a gear 1,2.2.2 addendum 1.2.1.3 toothing part of agear tooth between the reference surface and the tip surface complete set of teeth of a toothed component 1.2.2.3 1.2.1.4 top land pitch portion of the tip surface between opposite flanks dimension defining the uniform spacing, in any of a tooth specified direction, of adjacent corresponding tooth profiles --–1.2.2.3 1,2.21— ---” — : — 1.2.2,2 1.2.1.5 &-- — Y :;l, module /,, ‘? > P,””’ quotient of the pitch at the reference surface, \>\_ ,,‘,2 expressed in millimetres, divided by n * ~~ IJByconvention,thequalification“reference”maybe implied, 1.2.2.4 unlessacleardistinction between“reference”and“operating” ISnecessary, Usethe qualification “tooth reference’’ when root surface there may otherwise be arisk ofconfusion with specially machined datum surfaces whicharealsotermed “referen ce coaxial surface of revolution bounding the inner surfaces”. extremities of external gear tooth spaces or the 4 IS 2458:2001 ISO 1122-1:1998 outer extremities of internal gear tooth spaces &,.*.*.& ‘“’”’”2=: 1.2.2.5 1.2.2.9 dedendum external gear pair part of agear tooth between the reference surface gear pair in which both gears are external gears and the root surface 1.2.2.6 bottom land I!3 part of the root surface between the fillets 1.2.2.7 external gear gear of which the tip surface is external to the root surface NOTES 1 Inorder to avoid any ambiguity, especially inthe case of bevel gears, consider the section of both surfaces by aplane perpendicular to the axis ofthe gears. 1.2.2.10 2 Arack (2.1.7.1 )isconsidered to beanexternal gear. internal gear pair ..--- ., gear pair in which one of the gears is an internal gear 1.2.2.8 internal gear gear of which the tip surface is internal to the root surface 5