Crank assembly for a bicycle bottom bracket assembly, shaft and crank arm thereof

Abstract

A crank assembly for a bicycle's bottom bracket assembly comprises a shaft extending along a longitudinal axis, at least one crank arm associated with at least one free end of said shaft, first front coupling means formed on said shaft and second front coupling means formed on said at least one crank arm, said first and second front coupling means being coupled together. In particular, the aforementioned first and second front coupling means comprise respective front toothings. The front coupling is located in an end zone, or on the outside, of a bottom bracket assembly's shaft's housing box formed in the bicycle's frame. The front coupling introduces a structural discontinuity between crank arm and shaft, for which reason the bending load exerted on the crank arm during pedaling is transmitted to the shaft to a small degree. Such a structural discontinuity is located at the shaft/crank arm interface

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention shall become clearer from the following detailed description of some preferred embodiments thereof, made with reference to the attached drawings. In such drawings:

FIG. 1 is a schematic view of a longitudinal section of a first embodiment of a bottom bracket assembly comprising a first embodiment of a crank assembly in accordance with the present invention;

FIG. 2 is a view identical to that of FIG. 1 wherein the shaft and the corresponding coupling portion of the crank arm are represented not in section;

FIG. 3 is an enlarged side schematic view of the shaft-crank arm coupling zone of the crank assembly illustrated in FIG. 1;

FIG. 3A is a second enlarged side schematic view of the shaft-crank arm coupling zone of the crank assembly illustrated in FIG. 1;

FIG. 4 is a schematic view of a cross section of the shaft-crank arm coupling zone of FIG. 3 taken along the lines III-III;

FIG. 5 is a schematic perspective view of the right crank arm of the crank assembly illustrated in FIG. 1;

FIG. 6 is a schematic view of a longitudinal section of a second embodiment of a bottom bracket assembly comprising the crank assembly illustrated in FIG. 1;

FIG. 7 is a schematic view of a longitudinal section of a bottom bracket assembly comprising an alternative embodiment of a crank assembly in accordance with the present invention;

FIG. 8 is a schematic view of a longitudinal section of an end portion of a bottom bracket assembly comprising a further embodiment of a crank assembly in accordance with the present invention;

FIG. 9 is a schematic perspective view of the right crank arm of the crank assembly illustrated in FIG. 8;

FIG. 10 is a schematic view, partially in longitudinal section, of a further embodiment of a bottom bracket assembly comprising the crank assembly illustrated in FIG. 1;

FIG. 11 shows a detail of the crank arm of FIG. 5;

FIG. 12 shows a racing bicycle that comprises the bottom bracket assembly of FIG. 1; and

FIG. 13 is a view identical to that of FIG. 1 wherein the shaft and the corresponding coupling portion of the crank arm are represented not in section.

Claims

1. Crank assembly for a bicycle bottom bracket assembly, comprising: a shaft extending along a longitudinal axis;at least one crank arm associated with at least one free end of said shaft;coupling means between said shaft and said at least one crank arm;wherein said coupling means comprise first front coupling means formed on said at least one free end of said shaft and second front coupling means formed on said at least one crank arm said first and second front coupling means being coupled together.

2. Crank assembly according to claim 1, wherein said first front coupling means comprise first rotation-driving means and said second front coupling means comprise second rotation-driving means.

3. Crank assembly according to claim 2, wherein said first rotation-driving means comprise a first front toothing extending circumferentially on a front end surface of said shaft and said second rotation-driving means comprise a second front toothing extending circumferentially on a front end surface of a coupling portion of said crank arm with said shaft.

4. Crank assembly according to claim 1, further comprising centering means of said at least one crank arm with respect to said shaft.

5. Crank assembly according to claim 3, further comprising centering means of said at least one crank arm with respect to said shaft, wherein said centering means are defined by said first and second front toothings.

6. Crank assembly according to claim 3, wherein said first and second front toothings comprise a plurality of identical and symmetrical teeth, each tooth of said plurality of teeth comprising a pair of side surfaces inclined, along a direction parallel to said longitudinal axis, so as to form an angle α between them having a first predetermined value.

7. Crank assembly according to claim 6, wherein said first value is between 14° and 40°.

8. Crank assembly according to claim 7, wherein said first value is equal to 27°.

9. Crank assembly according to claim 6, wherein said side surfaces of said tooth are inclined with respect to a radial plane containing said longitudinal axis, so as to form an angle β between them having a second predetermined value.

10. Crank assembly according to claim 6, wherein said first and second front toothings comprise a plurality of throats, wherein each throat is defined between two adjacent teeth and has a curved base surface joined to said side surfaces of said teeth.

11. Crank assembly according to claim 1, wherein said at least one crank arm comprises a seat for housing a bearing adapted to allow the rotation of the bottom bracket assembly with respect to a housing box of said shaft formed in a frame of a bicycle.

12. Crank assembly according to claim 11, wherein said first rotation-driving means comprise a first front toothing extending circumferentially on a front end surface of said shaft and said second rotation-driving means comprise a second front toothing extending circumferentially on a front end surface of a coupling portion of said crank arm with said shaft, wherein said seat is defined by an outer surface of said coupling portion of said at least one crank arm.

13. Crank assembly according to claim 11, wherein said first rotation-driving means comprise a first front toothing extending circumferentially on a front end surface of said shaft and said second rotation-driving means comprise a second front toothing extending circumferentially on a front end surface of a coupling portion of said crank arm with said shaft, wherein said at least one crank arm comprises a substantially annular crank arm body portion radially outside with respect to said coupling portion and wherein said seat is defined by an inner surface of said substantially annular crank arm body portion.

14. Crank assembly according to claim 11, further comprising a rolling bearing associated with said at least one crank arm at said seat.

15. Crank assembly according to claim 1, wherein said at least one crank arm is a right crank arm.

16. Crank assembly according to claim 1, wherein said at least one crank arm is a left crank arm.

17. Crank assembly according to claim 1, wherein said shaft comprises a central portion and opposite end portions and wherein said central portion has a diameter greater than that of said opposite end portions.

18. Bottom bracket assembly of a bicycle, comprising a crank assembly according to claim 1.

19. Bottom bracket assembly according to claim 18, wherein the shaft of said crank assembly is made in a single piece with a crank arm opposite the crank arm of said crank assembly.

20. Bottom bracket assembly according to claim 18, wherein the shaft of said crank assembly is made in two separate pieces coupled together through second coupling means.

21. Bottom bracket assembly according to claim 20, wherein said second coupling means are front coupling means.

22. Bottom bracket assembly according to claim 18, wherein the crank arm of said crank assembly is a right crank arm or a left crank arm and wherein the other crank arm is coupled with said shaft through a threaded coupling.

23. Shaft for a bicycle bottom bracket assembly, comprising a body extending along a longitudinal axis, said body comprising, at least one free end thereof, coupling means with at least one crank arm wherein said coupling means comprise front coupling means.

24. Shaft according to claim 23, wherein said front coupling means comprise rotation-driving means of said at least one crank arm.

25. Shaft according to claim 23, further comprising centering means of said at least one crank arm with respect to said shaft.

26. Shaft according to claim 24, wherein said rotation-driving means comprises a front toothing extending circumferentially on a front end surface of said body.

27. Shaft according to claim 26, wherein said front toothing comprises a plurality of identical and symmetrical teeth, each tooth of said plurality of teeth comprising a pair of side surfaces inclined, along a direction parallel to said longitudinal axis, so as to form an angle α between them having a first predetermined value.

28. Shaft according to claim 27, wherein said first value is between 14° and 40°.

29. Shaft according to claim 28, wherein said first value is equal to 27°.

30. Shaft according to claim 27, wherein said side surfaces of said tooth are inclined with respect to a radial plane containing said longitudinal axis, so as to form an angle β between them having a second predetermined value.

31. Shaft according to claim 27, wherein said front toothing comprises a plurality of throats, wherein each throat is defined between two adjacent teeth and has a curved base surface joined to said side surfaces of said teeth.

32. Shaft according to claim 23, comprising, at an end portion thereof, an outer threading.

33. Shaft according to claim 23, wherein said body comprises a central portion and opposite end portions, wherein said central portion has a diameter greater than that of said end portions.

34. Shaft according to claim 23, wherein said body is made in a single piece.

35. Shaft according to claim 23, wherein said body is made in two separate pieces coupled together through second coupling means.

36. Shaft according to claim 35, wherein said second coupling means are front coupling means.

37. Crank arm of a bicycle, comprising a body having a coupling portion with a shaft of a bottom bracket assembly of a bicycle, said coupling portion extending along an axis and comprising, at a free end thereof, coupling means with said shaft, wherein said coupling means comprise front coupling means.

38. Crank arm according to claim 37, wherein said front coupling means comprise rotation-driving means of said shaft.

39. Crank arm according to claim 37, further comprising centering means of said shaft with respect to said crank arm.

40. Crank arm according to claim 38, wherein said rotation-driving means comprise a front toothing extending circumferentially on a front surface of said coupling portion of said crank arm body.

41. Crank arm according to claim 40, wherein said front toothing comprises a plurality of identical and symmetrical teeth, each tooth of said plurality of teeth comprising a pair of side surfaces inclined, along a direction parallel to said longitudinal axis, so as to form an angle α between them having a first predetermined value.

42. Crank arm according to claim 41, wherein said first value is between 14° and 40°.

43. Crank arm according to claim 42, wherein said first value is equal to 27°.

44. Crank arm according to claim 41, wherein said side surfaces of said tooth are inclined with respect to a radial plane containing said longitudinal axis, so as to form an angle β between them having a second predetermined value.

45. Crank arm according to claim 41, wherein said front toothing comprises a plurality of throats, wherein each throat is defined between two adjacent teeth and has a curved base surface joined to said side surfaces of said teeth.

46. Crank arm according to claim 37, comprising a seat for housing a bearing adapted to allow the rotation of said crank arm when associated with said shaft, with respect to a housing box of said shaft formed in a frame of a bicycle.

47. Crank arm according to claim 46, wherein said seat is defined by an outer surface of said coupling portion of said crank arm body.

48. Crank arm according to claim 46, comprising a substantially annular crank arm body portion radially outside with respect to said coupling portion, said seat being defined by an inner surface of said substantially annular crank arm body portion.

49. Crank arm according to claim 37, wherein said crank arm is a right crank arm.

50. Bicycle, comprising a frame provided with a housing box of a shaft of a bottom bracket assembly, said shaft extending along a longitudinal axis, said bottom bracket assembly also comprising a pair of crank arms at least one crank arm of said pair of crank arms being associated with at least one free end of said shaft, and coupling means between said shaft and said at least one crank arm; wherein said coupling means comprise first front coupling means formed on said shaft and second front coupling means formed on said at least one crank arm said first and second front coupling means being coupled together.

51. Bicycle according to claim 50, wherein said first and second front coupling means are arranged at an end zone of said box.

52. Bicycle according to claim 50, wherein said first and second front coupling means are arranged outside said box.

53. Bicycle according to claim 50, also comprising a pair of bearings suitable for allowing the rolling of said bottom bracket assembly in said box, wherein at least one bearing of said pair of bearings is arranged outside said box and at a seat defined on said at least one crank arm of said pair of crank arms.

54. Crank assembly for a bicycle bottom bracket assembly, comprising: a shaft extending along a longitudinal axis;at least one crank arm associated with at least one free end of said shaft; anda coupling between said shaft and said at least one crank arm;wherein said coupling comprises first front couples formed on said at least one free end of said shaft and second front couples formed on said at least one crank arm said first and second front couples being coupled together.

55. Crank assembly for a bicycle bottom bracket assembly, comprising: a shaft extending along a longitudinal axis;at least one crank arm associated with at least one free end of said shaft; anda Hirth coupling between said shaft and said at least one crank arm.

56. A crank arm of a bicycle, comprising a body having a coupling portion with a shaft of a bottom bracket assembly of a bicycle, said coupling portion extending along an axis and comprising, at a free end thereof, a coupling with said shaft, wherein said coupling comprises front coupling, wherein said front coupling comprises a front toothing that rotationally drives said shaft, andwherein said front toothing extends circumferentially on a front surface of said coupling portion.

57. Crank arm according to claim 56, wherein said front toothing comprises a plurality of identical and symmetrical teeth, each tooth of said plurality of teeth comprising a pair of side surfaces inclined, along a direction parallel to said longitudinal axis, so as to form an angle α between them having a first predetermined value.

58. Crank arm according to claim 57, wherein said side surfaces of said teeth are inclined with respect to a radial plane containing said longitudinal axis, so as to form an angle β between them having a second predetermined value.

59. Crank assembly for a bicycle bottom bracket assembly, comprising a first crank arm comprising a Hirth coupling to a second crank arm with a mating Hirth coupling, wherein the mated Hirth couplings are located equidistant from each of the first and second crank arm.

60. Crank assembly for a bicycle bottom bracket assembly, comprising a first crank arm having a Hirth coupling to a second crank arm, wherein the Hirth coupling, when coupled, is located closer to one of the first or second crank arm.