Bicycle chainring and a bicycle comprising the bicycle chainring

Abstract

The present invention relates to a bicycle chainring (1) for engagement with a drive chain provided with rollers, the bicycle chainring (1) comprising: a plurality of teeth (2, 3) extending radially from a periphery of the chainring (1), wherein the plurality of teeth (2, 3) comprises a plurality of narrow teeth (3) and a plurality of wide teeth (2), wherein each tooth (2, 3) comprises a front flank (5) and a rear flank (6) with respect to a drive direction (DD) and two opposing side surfaces (9), wherein at least one side surface (9) of each wide tooth (2) comprises a protrusion (7) extending therefrom in an axial direction of the chainring (1), wherein each protrusion (7) comprises a respective groove (8) arranged halfway between a top land (10) of the respective wide tooth (2) and a root circle (11) of the respective wide tooth (2), wherein the groove (8) extends throughout the protrusion (7) in a direction substantially parallel to the top land (10). The invention further relates to a bicycle comprising the of the invention chainring (1).

Claims

1. A bicycle chainring for engagement with a drive chain provided with rollers, the bicycle chainring comprising: a plurality of teeth extending radially from a periphery of the chainring, wherein the plurality of teeth comprises a plurality of narrow teeth and a plurality of wide teeth, wherein each tooth comprises a front flank and a rear flank with respect to a drive direction and two opposing side surfaces, wherein at least one side surface of each wide tooth comprises a protrusion extending therefrom in an axial direction of the chainring, wherein each protrusion comprises a respective groove arranged halfway between a top land of the respective wide tooth and a root circle of the respective wide tooth, wherein the groove extends throughout the protrusion in a direction substantially parallel to the top land.

2. The bicycle chainring according to claim 1, wherein each side surface of each wide tooth comprises a respective protrusion.

3. The bicycle chainring according to claim 2, wherein the respective grooves in the opposing side surfaces of a wide tooth are equally sized.

4. The bicycle chainring according to claim 2, wherein the respective grooves in the opposing side surfaces of a wide tooth are differently sized.

5. The bicycle chainring according to claim 1, wherein the groove is shaped in a circular, an elliptical, a triangular, a trapezoidal or a rectangular form in cross-section, as seen in a tangential direction of the chainring, wherein the groove is preferably shaped in a triangular form.

6. The bicycle chainring according to claim 1, wherein the groove is defined by a radial width between two edges of the protrusion delimiting the groove in the radial direction and an axial depth in the axial direction at a deepest point of the groove, wherein the radial width is constant throughout the extension of the groove in the protrusion, and wherein preferably a ratio between the radial width of the groove and the axial depth of the groove is between 2 to 1 and 3 to 1.

7. The bicycle chainring according to claim 1, wherein the groove is defined by a radial width between two edges of the protrusion delimiting the groove in the radial direction and an axial depth in the axial direction at a deepest point of the groove, wherein the protrusion has an axial height at the edges of the protrusion delimiting the groove in the radial direction, and wherein the axial depth of the groove is from at least 30% of the axial height of the protrusion up to 70% of the axial height of the protrusion, preferably from about 40% of the axial height of the protrusion up to 70% of the axial height of the protrusion, and further preferably about 30% or 40% of the axial height of the protrusion, and wherein preferably the radial width is constant throughout the extension of the groove in the protrusion.

8. The bicycle chainring according to claim 1, wherein the groove is defined by a radial width between two edges of the protrusion delimiting the groove in the radial direction and an axial depth in the axial direction at a deepest point of the groove, wherein the two edges delimiting the groove are arranged symmetrically about a plane extending halfway between the top land of the respective wide tooth and the root circle of the respective wide tooth.

9. The bicycle chainring according to claim 1, wherein the plurality of teeth comprises an even number of teeth.

10. The bicycle chainring according to claim 1, wherein the plurality of wide teeth and the plurality of narrow teeth are arranged in an alternating manner, wherein preferably each wide tooth is followed by a narrow tooth and/or each narrow tooth is followed by a wide tooth.

11. The bicycle chainring according claim 1, wherein the plurality of wide teeth and the plurality of narrow teeth are arranged in an alternating manner, wherein each wide tooth is followed by three narrow teeth.

12. The bicycle chainring according to claim 1, wherein the chainring is circular or oval.

13. The bicycle chainring according to claim 1, wherein the chainring is planar or domed.

14. The bicycle chainring according to claim 1, wherein at least one protrusion comprises a chamfer facing the root circle.

15. A bicycle comprising a bicycle chainring according to claim 1.

Description

(1) FIG. 1 a perspective view of a first embodiment of the bicycle chainring;

(2) FIG. 2 a front view of the bicycle chainring of FIG. 1;

(3) FIG. 3 a side view of the bicycle chainring of FIG. 1;

(4) FIG. 4 a sectional view of the arrangement of FIG. 1 along the line IV-IV in FIG. 2;

(5) FIG. 5 an enlarged view of an upper part of FIG. 4;

(6) FIG. 6 a sectional view of the arrangement of FIG. 1 along the line VI-VI in FIG. 2;

(7) FIG. 7 an enlarged view of an upper part of FIG. 6;

(8) FIG. 8 an enlarged perspective view of the arrangement of FIG. 1 with particular emphasis on a wide tooth;

(9) FIG. 9 another enlarged perspective view of the arrangement of FIG. 1 with particular emphasis on a wide tooth;

(10) FIG. 10 a perspective view of a second embodiment of the bicycle chainring;

(11) FIG. 11 a front view of the bicycle chainring of FIG. 10;

(12) FIG. 12 a side view of the bicycle chainring of FIG. 10;

(13) FIG. 13 a sectional view of the arrangement of FIG. 10 along the line XIII-XIII in FIG. 12;

(14) FIG. 14 an enlarged view of an upper part of FIG. 13;

(15) FIG. 15 a sectional view of the arrangement of FIG. 10 along the line XV-XV in FIG. 11;

(16) FIG. 16 an enlarged view of an upper part of FIG. 15; and

(17) FIG. 17 an enlarged perspective view of the arrangement of FIG. 10 with particular emphasis on a wide tooth.

EMBODIMENTS OF THE INVENTION

(18) With reference to FIGS. 1 to 9, a first embodiment of a chainring 1 for a bicycle is described. As show, the bicycle chainring 1 is embodied as an oval chainring. However, as discussed above, the chainring can be embodied with a variety of shapes, including a circular shape, and the description below is applicable accordingly.

(19) The bicycle chainring 1 in this embodiment comprises a plurality of teeth 2, 3 and more specifically a plurality of wide teeth 2 and a plurality of narrow teeth 3. Each tooth of the plurality of wide teeth 2 comprises at least one and preferably two protrusions 7 extending respectively from both side surfaces 9 of the chainring 1, the extension being in an axial direction of the chainring 1. In this embodiment, the chainring 1 comprises an even number of teeth 2, 3 and an alternation between the teeth, wherein each wide tooth 2 is followed by a narrow tooth 3 and each narrow tooth 3 is followed by a wide tooth 2. The chainring 1 is preferably domed towards an Inboard side 16 of the chainring 1 as can be seen in FIGS. 3, 4 and 6. The outboard side Is indicated with reference numeral 15 in FIG. 4.

(20) With reference to FIGS. 5 and 8, in every protrusion 7, a groove 8 shaped in a triangular form in cross-section is provided, the groove 8 being arranged halfway between a top land 10 of the respective wide tooth 2 and a root circle 11 of the respective wide tooth 2. The term “arranged halfway between”, as above, designates a groove 8 extending throughout the protrusion 7, as shown particularly in FIGS. 5 and 8, such that the edges 7a of the protrusion 7 delimiting or adjacent to the groove 8 are located about a plane P extending halfway between the top land 10 of the respective wide tooth 2 and the root circle 11 of the respective wide tooth 2. Preferably, the edges 7a of the protrusion 8 delimiting the groove 8 are centered about said plane P.

(21) The groove 8 extends throughout the protrusion 7 in a direction substantially parallel to the top land 10. The grooves 8 in the protrusions 7 on the respective side surfaces 9 of a respective wide tooth 2 are preferably equally sized and positioned on the respective protrusions 7, as show in FIG. 5. The grooves 7 may also be symmetrical with respect to a not shown plane bisecting the wide tooth 2. Furthermore, all wide teeth 2 may preferably have an identical set of protrusions 7 with grooves 8 on the inboard side 15 and a mirrored identical set of protrusions 7 with grooves 8 on the outboard side 16. However, also not equally sized and positioned groves 7 may be provided.

(22) As shown in FIG. 8, the groove 8 is defined by a radial width RW between the two edges 7a of the protrusion 7 delimiting the groove 8 in the radial direction and an axial depth AD in the axial direction at a deepest point of the groove 8. In the embodiment shown, the radial width RW Is constant throughout the extension of the groove 7 in the protrusion 8. Nevertheless, the radial width RW may also be variable.

(23) The protrusion 7 has an axial height AH at the edges 7a of the protrusion 7 delimiting the groove 8 in the radial direction. The axial depth AD of the groove 8 is at least 30% of the axial height AH of the protrusion 7, preferably about 40% of the axial height AH of the protrusion 7. Further, the axial depth AD of the groove 8 may be up 70% of the axial height AH of the protrusion 7.

(24) A radial width RW of a respective groove 8 in this embodiment equals two times the size of the axial depth AD of the groove 8. The protrusion 7 of this embodiment further comprises a protrusion chamfer 7′ as can also be seen in FIG. 8.

(25) FIG. 6 and especially FIG. 7 show the narrow teeth 3 of this embodiment, the narrow teeth 3 not comprising any protrusions 7 or grooves 8.

(26) As is visible in FIGS. 1, 2, 8 and 9, each tooth of the plurality of teeth 2, 3 has a front flank 5 and a rear flank 6. The front and rear flanks 5, 6 are defined in respect to the drive direction DD of the chain ring 1. Between each front flank 5 of the plurality of teeth 2, 3 and the rear flank 6 of each respective adjacent tooth of the plurality of teeth 2, 3, a valley is 4 is provided.

(27) The root circle 11 is defined in respect to the lowest point of the valley 4 as seen in the radial direction.

(28) As known in the art, the root circle 11 describes a closed curve, in the shown embodiment a circle, around the chainring 1, in which the plurality of teeth 2, 3 is rooted in. The teeth 2, 3 extend outwardly from the root circle 11. Obviously, the root circle 11 follows the shape of the chainring 1, and in an elliptical chainring (not shown) the root circle 11 will have a matching elliptical outline.

(29) The root circle 11 of the first embodiment of FIGS. 1 to 9 is substantially tangent to the respective maximum depths of the valleys 4 between the teeth 2, 3 of the chainring 1. In the case of the circular chainring 1 shown in FIG. 2 the root circle 11 has substantially a circular shape while being substantially tangent to the respective maximum depths of the valleys 4 between the teeth 2, 3 of the chainring 1. In an elliptic chainring (not shown) the root circle 11 substantially follows the elliptical form of the chainring 1 while still being substantially tangent to the respective maximum depths of the valleys 4 between the teeth 2, 3 of the chainring 1.

(30) With further reference to FIGS. 1 to 9 it should be noted that the chainring 1 is domed at the inboard side 1. The chainring 1 includes a central mounting portion 12, a slanted section 13 and a planar section 14 in which the mounting portion 12 is provided. The domed configurations provide for advantages, as a spider for adjusting the chain line can be avoided as an additional part. FIG. 1 further indicates the top driving position TDP at which a not shown chain roller engages the chainring 1 and the bottom release position RBP, at which the not shown chain roller exists the chainring.

Second Embodiment

(31) With reference to FIGS. 10 to 17, a second embodiment of the inventive bicycle chainring 1 is described.

(32) The second embodiment is distinguished from the first embodiment in that the groove 8 is shaped with a curved cross section, in particular a semicircular circular cross-section as can be best seen in FIGS. 14 and 17. Further, the axial depth AD of the groove 8 is preferably about 40% of the axial height AH of the protrusion 7 or at least 40% up to 70% of an axial height AH of the protrusion 7.

(33) The invention as presently described is particularly advantageous in terms of its technical effects. In fact, as explained, due to the grooves provided in the protrusions of the wide teeth of the present Invention, the same scrape the dirt from the chain links or plates of the chain and hence improve functionality and durability. Field tests carried out on chainring with grooves on the protrusions of the wide teeth in muddy conditions showed that such chainrings dropped the chain only once in 10 consecutive tests, while chainrings without the grooves, as disclosed for instance in the above cited prior art, in the same conditions dropped 3 times. This was an improvement of 300%.

(34) The foregoing explanation of the embodiments describes the present invention exclusively in the context of examples. Of course, individual features of the embodiments can be freely combined with each other, provided that this is technically reasonable, without leaving the scope of the present invention.

LIST OF REFERENCE SIGNS

(35) 1 Chainring 2 Wide tooth 3 Narrow tooth 4 Recess 5 Front flank 6 Rear flank 7 Protrusion 7a Edge of the protrusion 7′ Protrusion chamfer 8 Groove 9 Side surface 10 Top land 11 Root circle 12 Central mounting portion 13 Slanted section 14 Planar section 15 Outboard side 16 Inboard side AD axial depth RW radial width DD Drive Direction TDP Top driving position BRP Bottom release position P Plane