Unformatted text preview: e same direct ion o Co njugate gear toot h act io n: toot h pro files desig ned to pro duce a co nst ant angu lar velo cit y rat io n during meshing o Theoret ically, it sho u ld be able t o arbit rarily cho o se a toot h pro file fo r o ne gear and t hen find a profile for the mat ing gear that gives conjugate actio n. INVOLUTE PROFILE o Mo st co mmo n used t oot h pro file o Pro vid es t heoret ically per fect co njugate act io n even when shaft cent er dist ances are no t exact ly correct o Invo lut e is t he o nly geo metr ic pro file t hat satisfies t he law o f conjug ate gear tooth action while maintaining a constant pressure angle ( i.e. the line of action is a straight line) as gears rotate FUNDAMENTALS OF MESHING GEARS o P it ch line velo cit y V = r v p = rgv g , therefore, p C p o g = o v p rg æ d g N g m N g ö ÷ = ç = = = v g r p ç d p N p m N p ÷ è ø 1 (d p + d g ) = 1 (N p + N g )m = r p + r g 2 2 o Pressure line represent s t he d irect io n in which t he resu lt ant fo rce act s between gears dur ing toot h contact o o o Pressure ang le ( f ) usually has a value o f 20 fo r both SI and I mper ial syst ems, o r 25 fo r Imper ial sometimes. It is the angle between pressure line and common tangent ial line o f the two pitch circles.
o Dist ance o f cent ers is equal t o 4 MECH323 – 2007 GEARS____________________________ rb = r cos f o Fir st po int o f cont act is between meshing gears o ccurs where addendu m circle o f dr iven gear cro sses...
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- Fall '09
- gear, po int, pitch diameter, ang le, Pitch circle Pitch