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1、S T D - A L M A Lb-A-ENGL 1797 m b87575 0005332 b87 m ANSIIAGMA 1006-A97 AMERICAN NATIONAL STANDARD Tooth Proportions for Plastic Gears AGMA STANDARD Tooth Proportions for Plastic Gears American ANSI/AGMA 1006-A97 Standard National Approval of an American National Standard requires verification by A
2、NSI that the require- ments for due process, consensus, and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests
3、. Substantial agreement means much more than a simple majority, but not necessarily una- nimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. The use of American National Standards is completely voluntary; their existenc
4、e does not in any respect preclude anyone, whether he has approved the standards or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standards. The American National Standards Institute does not develop standards and will in no circums
5、tances give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Requests for interpre- tation of this standard should be addres
6、sed to the American Gear Manufacturers Association. CAUTION NOTICE: AGMA technical publications are subject to constant improvement, revision, or withdrawal as dictated by experience. Any person who refers to any AGMA Technical Publication should be sure that the publication is the latest available
7、from the Association on the subject matter. Fables or other self-supporting sections may be quoted or extracted. Credit lines should read: Extracted from ANSVAGMA 1006-A97, Tooth Proportions for Plastic Gears, with the permission of the publisher, the American Gear Manufacturers Association, 1500 Ki
8、ng Street, Suite 201, Alexandria, Virginia 22314.1 Approved August 7,1997 ABSTRACT This standard presents a new basic rack, AGMA PT, which, with its full round fillet, may be preferred in many applications of gears made from plastic materials. It also explains and illustrates the general concept of
9、the basic rack. It contains adescription, with equations and sample calculations, of how the proportions of a spur or helical gear may be derived from the design tooth thickness and the basic rack data. These equations and calculations use traditional AGMA symbols and inch units. In several annexes,
10、 there are discussions of pos- sible variations from this basic rack and also a procedure for defining tooth proportions without using the basic rack concept. Published by American Gear Manufacturers Association 1500 King Street, Suite 201, Alexandria, Virginia 22314 Copyright O 1997 by American Gea
11、r Manufacturers Association All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States of America II AMERICAN NATIONAL STANDARD ANSI/AGMA 1006-A97 Cont
12、ents Page Foreword . iv 1 1 Scope . 2 Definitions and symbols 1 Tooth proportions and basic rack 3 Standard basic rack for plastic gears . 3 Gear tooth proportions from basic rack data 8 3 4 5 Tables 1 2 Nomenclature: symbols and terms 1 Standard basic racks (based on unit pitch) 4 1 2 3 AGMA PT bas
13、ic rack (for pd or P d = 1) . 3 Example of AGMA PT basic rack modified with tip relief 5 Comparison of calculated bending stresses at fillets from AGMA Fine-Pitch and AGMA PT basic racks . 6 4(a) Effect of fillet shape on mold flow 7 location) . 7 4(c) Effect of fillet shape on fillet surface temper
14、ature during fteezing . 7 4(b) Effect of fillet shape on fiber orientation close to surface (at mid-facewidth 4(d) Comparison of shrinkage effect in undercut pinion with sharp and rounded 5 fillets 8 Tooth outline features introduced by tip rounding on external gears 11 Annexes A Basic rack descript
15、ion and application 13 Experimental basic racks for plastic gears . 21 Gear tip relief from a modified basic rack 27 E Alternate practices for defining tooth proportions . 31 Generating spur gear geometry without racks 37 G Sample calculations 43 6 C D Determination of tooth thickness and other desi
16、gn variables 23 F Bibliography . 47 . I l l ANWAGMA 1006-A97 AMERICAN NATIONAL STANDARD Foreword r h e foreword, footnotes, and annexes are provided for informational purposes only and should not be construed as a part of ANSVAGMA 1006497, Tooth Proportions for Plastic Gears. AGMA has issued standar
17、ds for gear tooth proportions over a period of many years. The most recent versions have been AGMA 201 .O2 (withdrawn 1995), Tooth Proportions for Coarse-Pitch Involute Spur Gears, and ANWAGMA 1003-G93, Tooth Proportions for Fine-Pitch Involute Spur and Helical Gears. These standards and their prede
18、cessors were prepared in response to the need to standardize gear generating cutting tools such as hobs and shaper cutters. Without such standards, the variety of tools needed by gear shops would have become unlimited. The manufacture of gears by the molding process is not subject to the same practi
19、cal constraints as manufacture by the gear cutting process. Every mold is inherently “non-standard“. The geometry of the mold cavity cannot follow a standard because of varying allowances for shrinkage. Furthermore, there are some methods for manufacturing the mold cavity which do not depend on cutt
20、ing tools and, even for those that do, special tools are generally required. Thus, tooth proportions for molded plastic gears need not follow those established for machined gears. Some of the special properties of plastic materials influence the selection of gear tooth proportions as the two followi
21、ng examples illustrate: - The structure and orientation of plastic molecules, regardless of processing method, makes the strengths of the materials particularly sensitive to sharp internal corners. A substantially stronger tooth will result if sharp fillets at the base of the tooth are avoided. The
22、tooth proportions for gears made according to the AGMA fine-pitch standard noted above generally result in relatively sharp fillets. - In certain applications, the higher expansion properties of plastic materials may create the need for a greater depth of engagement between mating gears than permitt
23、ed by the other standard tooth forms. As a result of this preference for a different tooth form, members of the plastic gear molding industry have adopted their own individual sets of tooth proportions. One set that has gained wide usage by plastic gear designers, and is often specified in place of
24、the AGMA Fine-Pitch Standard, has been developed by William McKinley i. Because these tooth forms contain the preferential features for molded plastic gears and because they are already well recognized in the industry, they were used, with some changes, as models in the preparation of this standard.
25、 The first of the four variations in this set has a depth of engagement, or working depth, that is the same as in the above mentioned AGMA standards. The other three have increased depths of engagement in varying degrees. This standard has selected only the first variation, which is the one in wides
26、t use, as the model for the new tooth proportions. However, data similarly based on the other three variations are included in annex B. The tooth forms in this standard are defined with the use of the basic rack concept. For those that might be unfamiliar with this concept, a detailed description of
27、 the basic rack is included as annex A. Suggestions for improvement of this standard will be welcome. They should be sent to the American Gear Manufacturers Association, 1500 King Street, Suite 201, Alexandria, Virginia 22314. iv STD-AGHA LOOb-A-ENGL 1777 = Ob87575 0005325 37b H AMERICAN NATIONAL ST
28、ANDARD PERSONNEL of the AGMA Plastics Gearing Committee Chairman: I. Laskin . Irving Laskin, P.E. Vice Chairman: H. Yelle Ecole Polytechnique de Montral ACTIVE MEMBERS M.A. Bennick . RTP Company R. Casavant GW Plastics, Inc. D. Castor . Eastman Kodak Company C.M. Denny . Consultant D.S. Ellis . ABA-
29、PGT, Inc. K. Gitchel Universal Tech. Systems, Inc. J.W. Kelley . Shell Chemical Company R. Kleiss . Kleiss Engineering S. Legault Seitz Corporation A. Milano . Seitz Corporation ASSOCIATE MEMBERS J. Ambrosina . M.K. Anwar . D. Bailey . R.E. Bergmann F. Boss . K. Buyukataman . A. Conrad P. Danish . P
30、. Davoli . W.T. Derry E. Dornan L. Faure C. Fleenor M. Fletcher . D. Fritzinger R.J. Galipeau . T. Grula P.M. Hughes S LeGault IDEO Product Development Allied Devices Corporation Rochester Gear, Inc. Gear Research Institute DSM Engineering Plastics UTC Pratt inside tip land Normal tooth thickness at
31、 standard pitch diameter Normal tooth thickness at inside diameter of helical internal gear; normal inside tip land Normal tooth thickness at outside diameter of helical external gear; normal top land Effective normal top land with tip rounding Remaining normal top land with tip rounding Tooth thick
32、ness at outside diameter of spur external gear; top land Effective top land with tip rounding Remaining top land with tip rounding Transverse tooth thickness at inside diameter of internal helical gear Transverse tooth thickness at outside diameter of external helical gear Rack shift Helix angle at
33、standard pitch diameter Helix angle at inside diameter of internal helical gear Helix angle at outside diameter of external helical gear Profile angle of basic rack; pressure angle at standard pitch diameter of spur gear; normal pressure angle at standard pitch diameter of helical gear Pressure angl
34、e at inside diameter of spur internal gear Normal pressure angle at outside diameter of helical external gear Pressure angle at outside diameter o f spur gear Transverse pressure angle at standard pitch diameter of helical gear Transverse pressure angle at inside diameter of internal helical gear Tr
35、ansverse pressure angle at outside diameter of external helical gear First Used Figure 1 Figure 1 Eq 1 Eq 5 Eq 6 Eq 9 Eq 3 Eq 29 Eq 4 Figure 1 Figure 1 5.1 Figure 1 CIS 5 CIS 5 Figure 2 Figure 1 Eq 28 Figure 1 5.1 Figure 1 Eq 12 5.4 Eq 27 Eq 23 Eq 34 Eq 32 Eq 8 Eq 30 f q 28 Eq 25 Eq 21 Eq 2 5.4 Iq 2
36、6 -igure 1 -q 22 -. : q 11 -9 31 I q 7 Eq 17 Eq 24 - Eq 20 S T D - A G H A LOOb-A-ENGL 2777 b87575 0005327 T32 AMERICAN NATIONAL STANDARD ANSIIAGMA 1006-A97 3 Tooth proportions and basic rack experimental basic racks with greater working depths are defined in annex B.) It is general practice to esta
37、blish a system of tooth proportions by defining a basic rack. The actual tooth outline for a gear with a specified number of teeth and value of tooth thickness will be generally determined by the generating action o f this rack- shaped outline. (Some features of the tooth outline may be determined b
38、y additional considerations. See 5.8.1, 5.8.2 and 5.8.3.) A description of this basic rack concept and how it is applied to various NOTE: This basic rack is an optional alternative to other AGMA basic racks. It will often be preferred for those applications in which tooth bending strength is a major
39、 factor in the design of plastic gears. See 4.4. 4.1 Designations This basic rack is designated as: AGMA Plastic Gearing Toothform, abbreviated as: AGMA PT. types of gears is given in annex A. 4.2 Proportions 4 Standard basic rack for plastic gears The basic rack is shown in figure 1. The figure ide
40、ntifies all the features described in A.2. Values of the dimensional features are listed in table 2 along with comparative values for the AGMA fine-pitch standard and the IS0 mostly coarse-pitch standard. All of these values are referenced to unit pitch. Actual values are found by dividing the table
41、 values A standard basic rack is established in this AGMA standard. Plastic gears with tooth forms defined by this basic rack will mesh properly with both AGMA fine-pitch and IS0 coarse-pitch gears. (Three by the diametral pitch. Dimensional features: a g = addendum is the tooth thickness of the bas
42、ic rack; I R Almost all of the features defining a spur gear can be derived from the standard basic rack for the specified diametral pitch, Pd, and a few items of primary gear data. This is also true for a helical gear, with the specified diametral pitch of the basic rack becoming the normal diametr
43、al pitch, Pd, of the gear and the profile angle of the basic rack becoming the normal profile angle, , of the gear. Sample calculations illustrating the use of the equations in this section are supplied in annex G. is the profile angle of the basic rack; pres- sure angle at the standard pitch diamet
44、er of a spur gear; normal pressure angle at the standard pitch diameter of a helical gear. Outside diameter of the external gear, 6, is: 6 = d + 2y + BR where UBR is addendum of basic rack. 5.2.2 Root diameter . . . (3) 5.1 Primary gear data for spur gears The root diameter of the gear, Rack shift,
45、y. See A.7.1 and figures A.7 and A.8. - BR y = 2tm .( 2) where 8 where bFBR iS form dedendum Of basic rack (distance from pitch line to start of fillet radius). NOTE: This equation applies only for gears that are not undercut. The condition of no undercut is met if the term in brackets is equal to o
46、r greater than zero. The analybcal method for finding the form diameter for undercut gears is beyond the scope of this document. STD-AGUA ZOOb-A-ENGL 1997 Db87575 0005325 235 W - AMERICAN NATIONAL STANDARD ANSIIAGMA 1006-A97 5.2.4 Top land exact form can be found by graphically reproducing the gener
47、ating action. This form can often be closely approximated by a single circular arc. The ana,ytica, methods for finding the exact form and its The involute pressure angle at the outside diameter of a spur gear, h, is: approximation are beyond the scope of this 5m4 o = cos-1 - . . . (7) document. du T
48、he tooth thickness at the outside diameter of a spur external gear, or top land, r , is: gear data for helical gears - number of teeth, N; d - + inv - inv .( 8) - normal tooth thickness, t,; - helix angle, 9. 01 to = *; 5.2.5 Fillet form The form of the fillet can be found by graphically reproducing
49、 the generating action of the basic rack. The analytical method is beyond the scope of this document. See 2, 3, 4 and 5 in the Bibliography. 5.3 Derived gear data for internal spur gears 5.5 Derived gear data for external helical gears 5.5.1 Outside diameter Also see 5.8.1.1. The standard pitch diameter of the gear, d, is: . . . (1 3) N d = 5.3.1 Inside diameter P w dl = d -5 -.QR NOTE: The inside diameter should not be smaller than the base circle diameter. .( 9) is helix angle at the standard pitch diameter. Rack shift, y. 5.3.
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