GEARWHEEL FOR MOTION TRANSMISSION SYSTEMS ONTO CYCLES

Abstract

The gearwheel for motion transmission systems onto cycles is rotatable with respect to its center of rotation and comprises two gearwheel halves centrally symmetrical with respect to the center of rotation and both having a dragging profile adapted to enter at least partially in contact with a flexible element closed in a loop for the driving in motion of a cycle, with the dragging profile which comprises at least five sections having different curvatures between them and comprises a larger diameter and a smaller diameter whose ratio has a value between 1.31 and 1.39.

Claims

1. A gearwheel for motion transmission systems onto cycles which is rotatable with respect to its center of rotation and which comprises two gearwheel halves centrally symmetrical with respect to said center of rotation and both having a dragging profile adapted to enter at least partially in contact with a flexible element closed in a loop for the driving in motion of a cycle, wherein said dragging profile comprises at least five sections having different curvatures between them and comprises a larger diameter and a smaller diameter whose ratio has a value between 1.31 and 1.39.

2. The gearwheel according to claim 1, wherein said sections are defined by respective planar curves expressible in the plane by means of sixth-degree polynomials.

3. The gearwheel according to claim 1, wherein said sections comprise a first section defined by the curve: $y=\left(0\right).Math.x^6+\left(0\right).Math.x^5+\left(0\right).Math.x^4+\left(0\right).Math.x^3+\left(0\right).Math.x^2+\left(2.43685974131053.Math.*{10}^1\right).Math.x+\left(2.43685974131053.Math.*{10}^3\right)$ with x that belongs to the range of values comprised between (x.sub.0=100, x.sub.1=99.9).

4. The gearwheel according to claim 1, wherein said sections comprise a second section defined by the curve: $y=\left(-2.0484351380734.Math.*{10}^{-4}\right).Math.x^6+\left(-1.13122348471926.Math.*{10}^{-1}\right).Math.x^5+\left(-2.60131220581469.Math.*{10}^2\right).Math.x^4+\left(-3.18832920426384.Math.*{10}^3\right).Math.x^3+\left(-2.19676520438293.Math.*{10}^5\right).Math.x^2+\left(-8.06733158945192.Math.*{10}^6\right).Math.x+\left(-1.23364921739830.Math.*{10}^8\right)$ with x that belongs to the range of values comprised between (x.sub.1=99.9, x.sub.2=9.250048793*10.sup.1).

5. The gearwheel according to claim 1, wherein said sections comprise a third section defined by the curve: $y=\left(-1.7981184603777.Math.*{10}^{-8}\right).Math.x^6+\left(-6.82076299614828.Math.*{10}^{-6}\right).Math.x^5+\left(-1.06839175019891.Math.*{10}^{-3}\right).Math.x^4+\left(-8.823457473461434.Math.*{10}^{-2}\right).Math.x^3+\left(-4.06099748597368.Math.*1\right).Math.x^2+\left(-9.85445852908518.Math.*{10}^1\right).Math.x+\left(-8.49774277311171.Math.*{10}^2\right)$ with x that belongs to the range of values comprised between (x.sub.2=9.250048793*10.sup.1, x.sub.3=5.73195646810042*10.sup.1).

6. The gearwheel according to claim 1, wherein said sections comprise a fourth section defined by the curve: $y=\left(-1.09748855402908.Math.*{10}^{-10}\right).Math.x^6+\left(-1.43258624805134.Math.*{10}^{-9}\right).Math.x^5+\left(-1.07209710609252.Math.*{10}^{-6}\right).Math.x^4+\left(1.20396736523094.Math.*{10}^{-4}\right).Math.x^3+\left(-1.31217653209468.Math.*{10}^{-3}\right).Math.x^2+\left(-1.10301356697461.Math.*{10}^{-1}\right).Math.x+\left(1.34734234936338.Math.*{10}^2\right)$ with x that belongs to the range of values comprised between (x.sub.3=5.73195646810042*10.sup.1, x.sub.4=1).

7. The gearwheel according to claim 1, wherein said sections comprise a fifth section defined by the curve: $y=\left(0\right).Math.x^6+\left(0\right).Math.x^5+\left(0\right).Math.x^4+\left(0\right).Math.x^3+\left(0\right).Math.x^2+\left(-1.28328322234779.Math.*{10}^{-1}\right).Math.x+\left(1.3471477647095200.Math.*{10}^2\right)$ with x that belongs to the range of values comprised between (x.sub.4=1, x.sub.5=0).

8. The gearwheel according to claim 1, wherein said sections comprise a sixth section defined by the curve: $y=\left(1.06497537351313.Math.*{10}^{-10}\right).Math.x^6+\left(-1.75920494838167.Math.*{10}^{-8}\right).Math.x^5+\left(1.17118126041760.Math.*{10}^{-6}\right).Math.x^4+\left(-4.38563686202542.Math.*{10}^{-5}\right).Math.x^3+\left(-6.33628200012026.Math.*{10}^{-3}\right).Math.x^2+\left(-1.11203241802286.Math.*{10}^{-1}\right).Math.x+\left(1.34714776470952.Math.*{10}^2\right)$ with x that belongs to the range of values comprised between (x.sub.5=0, x.sub.6=5.74149838911238*10.sup.1).

9. The gearwheel according to claim 1, wherein said sections comprise a seventh section defined by the curve: $y=\left(-5.33273355491498.Math.*{10}^{-9}\right).Math.x^6+\left(2.25619449828721.Math.*{10}^{-5}\right).Math.x^5+\left(-3.95657580445826.Math.*{10}^{-3}\right).Math.x^4+\left(3.67739637477149.Math.*{10}^{-1}\right).Math.x^3+\left(-1.91001216673726.Math.*{10}^1\right).Math.x^2+\left(5.24683293546421.Math.*{10}^2\right).Math.x+\left(-5.82912465746677.Math.*{10}^3\right)$ with x that belongs to the range of values comprised between (x.sub.6=5.74149838911238*10.sup.1, x.sub.7=9.828620998080150*10.sup.1).

10. The gearwheel according to claim 1, wherein said sections comprise an eighth section defined by the curve: $y=\left(0\right).Math.x^6+\left(0\right).Math.x^5+\left(-3.64332093039957.Math.*1\right).Math.x^4+\left(1.43647113232435.Math.*{10}^3\right).Math.x^3+\left(-2.1238365829683.Math.*{10}^5\right).Math.x^2+\left(+1.39558401341522.Math.*{10}^7\right).Math.x+\left(-3.43886467319037.Math.*{10}^8\right)$ with x that belongs to the range of values comprised between (x.sub.7=9.828620998080150*10.sup.1, x.sub.8=99.99).

11. The gearwheel according to claim 1, wherein said sections comprise a ninth section defined by the curve: $y=\left(0\right).Math.x^6+\left(0\right).Math.x^5.Math..Math.\left(0\right).Math.x^4+\left(0\right).Math.x^3+\left(0\right).Math.x^2+\left(-2.821570196154020.Math.*{10}^2\right).Math.x+\left(2.821570196154020.Math.*{10}^4\right)$ with x that belongs to the range of values comprised between (x.sub.8=99.9, x.sub.9=+100).

12. The gearwheel according to claim 1, wherein each of said gearwheel halves comprises a toothed peripheral edge having a plurality of projecting elements spaced the one from the other by portions of said dragging profile.

13. The gearwheel according to claim 12, wherein said projecting elements comprise at least a first type of teeth of pointed shape adapted to guide said flexible element in a phase of decreasing thrust, and at least a second type of teeth of rounded shape adapted to guide said flexible element in a phase of increasing thrust.

14. The gearwheel according to claim 1, wherein said gearwheel comprises a larger diameter and a smaller diameter whose ratio is equal to 1.3574.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other characteristics and advantages of the present invention will appear better evident from the description of two preferred, but not exclusive, embodiments of a gearwheel for motion transmission systems onto cycles, illustrated by way of an indicative, but non-limiting, example in the accompanying drawings, wherein:

[0034] FIG. 1 is an axonometric view of the gearwheel according to the invention;

[0035] FIG. 2 is a plan view of a first embodiment of the gearwheel according to the invention;

[0036] FIG. 3 is a plan view of a second embodiment of the gearwheel according to the invention;

[0037] FIG. 4 is a schematic view of a detail of the gearwheel according to the invention.

EMBODIMENTS OF THE INVENTION

[0038] With particular reference to such figures, reference number 1 globally designates a gearwheel for motion transmission onto cycles.

[0039] The gearwheel 1 is rotatable with respect to its center of rotation C and can be split into two gearwheel halves 2 centrally symmetrical with respect to the center of rotation itself.

[0040] Conveniently, each of the gearwheel halves 2 comprises a toothed peripheral edge having a plurality of projecting elements 5, commonly called teeth.

[0041] There are regularly spaced the one from the other by portions of the dragging profile 3.

[0042] In particular, such teeth 5 define concavities wherein a flexible element closed in a loop, or commonly called chain, is intended to rest, for the dragging in motion of a cycle.

[0043] The projecting part of the tooth 5 is adapted to drag the flexible element in motion for a certain part of the pedaling.

[0044] Both gearwheel halves 2, in fact, have a dragging profile 3 adapted to enter at least partially in contact with the chain for the dragging in motion of a cycle.

[0045] The dragging profile 3 therefore coincides with the primitive profile of the toothed gearwheel halves 2.

[0046] According to the invention, the dragging profile 3 comprises at least five sections having different curvatures between them.

[0047] The aforementioned profile also comprises a larger diameter and a smaller diameter whose ratio has a value between 1.31 and 1.39.

[0048] Advantageously, the above value is equal to 1.3574.

[0049] In the present embodiment, the profile has a first section 11, a second section 12, a third section 13, a fourth section 14, a fifth section 15, a sixth section 16, a seventh section 17, an eight section 18 and a ninth section 19 connected to one another in sequence, having different curves and defined by respective planar curves expressible in the plane by means of sixth-degree polynomials.

[0050] In particular, these curves fall into the category of sestic curves and are curves of the following type:

y=a.sub.1x.sup.6+a.sub.2x.sup.5+a.sub.3x.sup.4+a.sub.4x.sup.3+a.sub.5x.sup.2+a.sub.6x+a.sub.7

[0051] where a.sub.n with n=1, 2, 3, 4, 5, 6, 7 are known terms and x, y the variables chosen for the graphic representation of such curves in the plane.

[0052] In this regard it is specified that, in the present treatise, the sestic curves defining the dragging profile 3 are defined with respect to the Cartesian reference system x, y, the origin of which coincides with the center of rotation C and to the minimum radius of the gearwheel half an arbitrary scale value of 100 has been given.

[0053] More in particular, the interception point of the curve for both x=100 and for x=100 is equal to y=0.

[0054] The first section 11 is defined by the curve

[00001]$y=\left(0\right).Math.x^6+\left(0\right).Math.x^5+\left(0\right).Math.x^4+\left(0\right).Math.x_3+\left(0\right).Math.x^2+\left(2.43685974131053.Math.*{10}^1\right).Math.x+\left(2.43685974131053.Math.*{10}^3\right)$

[0055] with x that belongs to the range of values comprised between (x.sub.0=100, x.sub.1=99.9).

[0056] The second section 12 is defined by the curve

[00002]$y=\left(-2.0484351380734.Math.*{10}^{-4}\right).Math.x^6+\left(-1.13122348471926.Math.*{10}^{-1}\right).Math.x^5+\left(-2.60131220581469.Math.*{10}^1\right).Math.x^4+\left(-3.18832920426384.Math.*{10}^3\right).Math.x^3+\left(-2.19676520438293.Math.*{10}^5\right).Math.x^2+\left(-8.06733158945192.Math.*{10}^6\right).Math.x+\left(-1.23364921739830.Math.*{10}^8\right)$

[0057] with x that belongs to the range of values comprised between (x.sub.1=99.9, x.sub.2=9.250048793*10.sup.1).

[0058] The third section 13 is defined by the curve

[00003]$y=\left(-1.7981184603777.Math.*{10}^{-8}\right).Math.x^6+\left(-6.82076299614828.Math.*{10}^{-6}\right).Math.x^5+\left(-1.06839175019891.Math.*{10}^{-3}\right).Math.x^4+\left(-8.82345747346134.Math.*{10}^{-2}\right).Math.x^3+\left(-4.06099748597368.Math.*1\right).Math.x^2+\left(-9.85445852908518.Math.*{10}^1\right).Math.x+\left(-8.49774277311171.Math.*{10}^2\right)$

[0059] with x that belongs to the range of values comprised between (x.sub.2=9.250048793*10.sup.1, x.sub.3=5.73195646810042*10.sup.1)

[0060] The fourth section 14 is defined by the curve

[00004]$y=\left(-1.09748855402908.Math.*{10}^{-10}\right).Math.x^6+\left(-1.43258624805134.Math.*{10}^{-9}\right).Math.x^5+\left(-1.07209710609252.Math.*{10}^{-6}\right).Math.x^4+\left(1.20396736523094.Math.*{10}^{-4}\right).Math.x^3+\left(-1.31217653209468.Math.*{10}^{-3}\right).Math.x^2+\left(-1.10301356697461.Math.*{10}^{-1}\right).Math.x+\left(1.34734234936338.Math.*{10}^2\right)$

[0061] with x that belongs to the range of values comprised between (x.sub.3=5.73195646810042*10.sup.1, x.sub.4=1).

[0062] The fifth section 15 is defined by the curve

[00005]$y=\left(0\right).Math.x^6+\left(0\right).Math.x^5+\left(0\right).Math.x^4+\left(0\right).Math.x^3+\left(0\right).Math.x^2+\left(-1.28328322234779.Math.*{10}^{-1}\right).Math.x+\left(1.3471477647095200.Math.*{10}^2\right)$

[0063] with x that belongs to the range of values comprised between (x.sub.4=1, x.sub.5=0).

[0064] The sixth section 16 is defined by the curve

[00006]$y=\left(1.06497537351313.Math.*{10}^{-10}\right).Math.x^6+\left(-1.75920494838167.Math.*{10}^{-8}\right).Math.x^5+\left(1.17118126041760.Math.*{10}^{-6}\right).Math.x^4+\left(-4.38563686202542.Math.*{10}^{-5}\right).Math.x^3+\left(-6.33628200012026.Math.*{10}^{-3}\right).Math.x^2+\left(-1.11203241802286.Math.*{10}^{-1}\right).Math.x+\left(1.34714776470952.Math.*{10}^2\right)$

[0065] with x that belongs to the range of values comprised between (x.sub.5=0, x.sub.6=5.74149838911238*10.sup.1).

[0066] The seventh section 17 is defined by the curve

[00007]$y=\left(-5.33273355491498.Math.*{10}^{-9}\right).Math.x^6+\left(2.25619449828721.Math.*{10}^{-5}\right).Math.x^5+\left(-3.95657580445826.Math.*{10}^{-3}\right).Math.x^4+\left(3.67739637477149.Math.*{10}^{-1}\right).Math.x^3+\left(-1.91001216673726.Math.*{10}^1\right).Math.x^2+\left(5.24683293546421.Math.*{10}^2\right).Math.x+\left(-5.82912465746677.Math.*{10}^3\right)$

[0067] with x that belongs to the range of values comprised between (x.sub.6=5.74149838911238*10.sup.1, x.sub.7=9.828620998080150*10.sup.1).

[0068] The eighth section 18 is defined by the curve

[00008]$y=\left(0\right).Math.x^6+\left(0\right).Math.x^5+\left(-3.64332093039957.Math.*1\right).Math.x^4+\left(1.43647113232435.Math.*{10}^3\right).Math.x^3+\left(-2.1238365829683.Math.*{10}^5\right).Math.x^2+\left(+1.39558401341522.Math.*{10}^7\right).Math.x+\left(-3.43886467319037.Math.*{10}^8\right)$

[0069] with x that belongs to the range of values comprised between (x.sub.7=9.828620998080150*10.sup.1, x.sub.8=99.99).

[0070] The ninth section 19 is defined by the curve

[00009]$y=\left(0\right).Math.x^6+\left(0\right).Math.x^5.Math..Math.\left(0\right).Math.x^4+\left(0\right).Math.x^3+\left(0\right).Math.x^2+\left(-2.821570196154020.Math.*{10}^2\right).Math.x+\left(2.821570196154020.Math.*{10}^4\right)$

[0071] with x that belongs to the range of values comprised between (x.sub.8=99.9, x.sub.9=+100).

[0072] Solutions cannot be ruled out which envisage the use of different curves, not necessarily sestic, having a geometrically similar pattern in the x, y plane.

[0073] In particular, all the curves are included having the same shape of the curves mentioned above and represented in scale with respect to these.

[0074] The dragging profile 3 so defined allows adapting the radius of the gearwheel, and therefore the resistance to motion provided by the vehicle, with respect to the thrust produced by the user on the basis of biomechanics of the leg.

[0075] Advantageously, the projecting elements 5 comprise a first type of teeth 6 and a second type of teeth 7.

[0076] The first type of teeth 6 is of pointed shape and is adapted to better guide the flexible elements mainly during the phase of decreasing thrust, i.e. during the phase in which the variable radius of the gearwheel tends to decrease upon rotating of same.

[0077] The second type of teeth 7 is of more rounded shape and is adapted to drag the flexible element in the remaining phases, i.e. when the variable radius of the gearwheel tends to increase and therefore during the phase of increasing thrust.

[0078] Both types have the same width at the contact portion 3.

[0079] The first type of teeth 6, furthermore, are higher than those of the second type 7 and permit better ensuring the guidance of the chain in the phases in which the falling off of the chain is more frequent, i.e., in the phases wherein the contact force between the chain and the gearwheel tends to decrease (phase of decreasing thrust).

[0080] In a first embodiment, shown in FIG. 2, the gearwheel 1 has forty-six projecting elements 5.

[0081] In a second embodiment, shown in FIG. 3, the gearwheel 1 has forty-eight projecting elements 5.

[0082] Different solutions cannot however be ruled out wherein the number of projecting elements is in a range between 28 and 54 projecting elements 5.

[0083] In any case, the gearwheel 1, rotating around the center of rotation C, causes a change in the radius according to the dragging profile 3, adapting itself, therefore, to the biomechanics of the joint.

[0084] The projecting elements 5, on the other hand, are arranged along the peripheral edge of the gearwheel 1 in such a way that the first type 6 comes into operation once it has crossed the larger radius and until it more or less reaches the smaller radius.

[0085] This way the possibility is minimized of the chain falling off precisely at the points where this occurs most frequently.

[0086] In practice it has been ascertained that the described invention achieves the intended objects and in particular the fact is underlined that the gearwheel for motion transmission onto cycles permits adapting the resistance to motion of the vehicle to the power developed by the user's leg.

[0087] The particular dragging profile, in fact, allows, during pedaling, a variation of the radius of the gearwheel proportional to the variation of the thrust which the leg is able to exert on the crankset.

[0088] The result is smoother and more regular pedaling, with the user able to adapt easily, without compromising his/her muscles or leg joints.