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1. (WO1998000656) SYSTEME DE PIGNON DE CHAINE A ROULEAUX PRESENTANT DES CARACTERISTIQUES SONORES AMELIOREES
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

Having thus described the preferred embodiments, the invention is now claimed to be:

1. A roller chain sprocket comprising:
a plurality of sprocket teeth each having an engaging flank and a coast flank;
a first tooth engaging flank cooperating with a second tooth coast flank to define an asymmetrical tooth space for receiving a roller associated with a roller chain; and
a flank flat positioned within the asymmetrical tooth space to permit a staged impact between the roller and the sprocket, wherein the staged impact includes an initial tangential impact between the roller and the sprocket along the flank flat followed by a subsequent radial impact between the roller and the sprocket which occurs a predetermined time period after the initial tangential impact.

2. The sprocket of claim 1, wherein the roller chain has a chain pitch and the sprocket has a chordal pitch which is less than the chain pitch to facilitate the staged impact between the roller and the sprocket.

3. The sprocket of claim 1, wherein the asymmetrical tooth space incorporates an engaging flank pressure angle which is in the range of about -2.0° to about +5° to facilitate the staged impact between the roller and the sprocket.

4. The sprocket of claim 1, wherein the flank flat is tangent to an engaging flank radius at a radially outer end thereof, and tangent to a root radius at a radially inner end thereof.

5. The sprocket of claim 1, further including an inclined root surface positioned along the engaging flank to provide tooth space clearance, and a root surface having a radius tangent to the flank flat at one end thereof and tangent to the inclined root surface at the other end thereof.

6. The sprocket of claim 5, wherein the root surface radius is less that a roller radius.

7. The sprocket of claim l, further including an inclined root surface positioned along the coast flank to provide tooth space clearance.

8. The sprocket of claim 1, further including a first inclined root surface positioned along the engaging flank, and a second inclined root surface positioned along the coast flank which cooperates with the first inclined root surface to provide tooth space clearance.

9. A unidirectional roller chain drive system comprising:
a driving sprocket having a plurality of sprocket teeth with each tooth having an engaging flank and a coast flank, the engaging flanks cooperating with the coast flanks of adjacent teeth to define asymmetrical tooth spaces between the sprocket teeth;
a driven sprocket having a plurality of sprocket teeth with each tooth having an engaging flank and a coast flank, the engaging flanks cooperating with the coast flanks of adjacent teeth to define asymmetrical tooth spaces between the sprocket teeth;
a roller chain having rollers in engaging contact with the driving sprocket and the driven sprocket; and each of the driving and driven sprocket teeth having a flank flat positioned along the respective engaging flanks to permit staged impacts between the rollers and the sprockets, wherein the staged impacts include initial tangential impacts between the rollers and the sprockets along the flank flats followed by subsequent radial impacts between the rollers and the sprockets which occur a predetermined time period after the initial tangential impacts occur.

10. The chain drive system of claim 9, wherein the roller chain has a chain pitch and the sprockets have a chordal pitch which is less than the chain pitch to facilitate the staged impacts between the rollers and the sprockets.

11. The chain drive system of claim 9, wherein the asymmetrical tooth spaces incorporate engaging flank pressure angles which are in the range of about -2.0° to about +5° to facilitate the staged impacts between the rollers and the sprockets.

12. The chain drive system of claim 9, wherein the flank flats are each tangent to an engaging flank radius at a radially outer end thereof, and tangent to a root radius at a radially inner end thereof.

13. The chain drive system of claim 9, wherein each asymmetrical tooth space includes an inclined root surface to provide tooth space clearance, and a radial root surface tangent to the flank flat at one end thereof and tangent to the inclined root surface at the other end thereof.

14. The chain drive system of claim 13, wherein the root surface radius is less that a roller radius.

15. The chain drive system of claim 9, wherein each asymmetrical tooth space includes an inclined root surface positioned along the coast flank to provide tooth space clearance.

16. The chain drive system of claim 9, wherein each asymmetrical tooth space includes a first inclined root surface positioned along the engaging flank, and a second inclined root surface positioned along the coast flank to provide tooth space clearance.

17. The chain drive system of claim 9, wherein the initial tangential impact and the subsequent radial impact facilitate spreading impact energy over a predetermined period of time to reduce meshing noise levels.

18. A method of engaging a roller chain with a sprocket having a plurality of sprocket teeth including an engaging flank which cooperates with an adjacent tooth coast flank to define an asymmetrical tooth space for receiving a roller associated with the roller chain, and including a flank flat positioned within the asymmetrical tooth space, the method comprising:
rotating the sprocket in a first direction so that the roller tangentially impacts the engaging flank along the flank flat; and
continuing to rotate the sprocket in the first direction so that the roller radially impacts a root surface of the sprocket a predetermined time period after impacting the engaging flank to spread the impact energy over the predetermined time period and reduce meshing noise levels.

19. The method of claim 18, further including:
after radially impacting the root surface, continuing to rotate the sprocket in the first direction so that the roller advances over an inclined root surface which facilitates maintaining the roller in hard contact with the root surface.

20. The method of claim 19, wherein the root surface is tangent to the flank flat at one end thereof and tangent to the inclined root surface at the other end thereof, and a radius of the root surface is less that a roller radius.

21. The method of claim 18, wherein the roller chain has a chain pitch and the sprocket has a chordal pitch which is less than the chain pitch to facilitate a staged impact between the roller and the sprocket.

22. The method of claim 18, wherein the asymmetrical tooth space incorporates an engaging flank pressure angle in the range of about -2.0° to about +5° to facilitate a staged impact between the roller and the sprocket.