Bicycle cassette with increased tooth ratio

A bicycle cassette with increased tooth ratio includes a driver body connected to a bicycle rear hub, and multiple cogs which are sequentially mounted to the driver body with equal spacing. An additional cog is mounted to the driver body and located opposite to the rear hub. The additional cog has 8-10 teeth. The tooth ratio is increased by the additional cog and the chainring to break through the limitation of tooth ratio of existing bicycle cassettes, and to increase the number of the gears of the bicycle cassette.

BACKGROUND OF THE INVENTION

1. Field of the Invention

2. Description of the Related Art

The conventional bicycle rear cassette generally includes a driver body which is integrally formed with the rear hub, and multiple cogs mounted to the driver body with a spacer located between each two adjacent cogs so that theses cogs are evenly spaced from each other. These cogs are mounted to the driver body in tooth-number sequence. The inner periphery of the driver body is coupled with the axle of the rear hub and the bearings, so that the minimum diameter and the maximum diameter of the driver body has to be maintained. The shape and size of the cogs of the cassette have a specific regulation. The inner diameter of the cassette is limited by the minimum diameter of the driver body, so that the smallest cog of the cassette is restricted as well. In the current bicycle industry, the minimum number of the teeth of the cogs is 11 which becomes the extreme number of the teeth for the cassette.

Take the road bicycles with an eighteen-gear derailleur system as an example, the system includes a 50/34 T compact crankset, and the rear cassette has 11-23 teeth. The tooth ratio is illustrated as follows:

The tooth ratio is related with the revolutions per minute of the pedal that the user operates. A larger tooth ratio can drive the bicycle at a higher speed for the same number of revolutions per minute of the pedal that the user operates. With a larger tooth ratio, the user needs to have stronger muscles, and has less cardiopulmonary burden. On the contrary, a smaller tooth ratio requires a higher number of revolutions per minute of the pedal that the user operates. With a smaller tooth ratio, the user does not require as strong muscles and, however, has more cardiopulmonary burden.

If the tooth ratio is to be changed, the change of the chainring is related to Bolt Circle Diameter (BCD). The crank may need to be replaced if the BCD does not fit, and this leads to higher expenses. The mainstream of the popular chainrings is 50/34 T or 52/36 T, while 53/39 T is barely used.

US2017/0369124A1 (US124 hereinafter) discloses a bicycle rear sprocket assembly with a wide range tooth ratio.FIGS.1to3are used to disclose the second sprocket, the first sprocket and the lock member.

The specific characters of the US124 are:

(1) The bicycle rear sprocket assembly1000includes the first sprocket1200and the lock member2600. The first sprocket1200includes the first opening2400, and the first torque-transmitting structure1800. The first opening2400has the first diameter D100that is smaller than the radially outer diameter D000of the sprocket support portion400. The first torque-transmitting structure1800is provided to the first bicycle inbound facing surface1400and configured to transmit pedaling torque to the second sprocket3800. It is possible to mount the first sprocket1200, which is a radially small sprocket having less than or equal to ten teeth, to the bicycle rear hub assembly with the lock member2600. Therefore, a bicycle to which the bicycle rear sprocket assembly1000is mounted can have a wide range of gear ratio.

(2) The first sprocket1200has the first total tooth number that is equal to or smaller than ten.

(3) The second sprocket3800includes the second bicycle inbound facing surface4000, the second torque-transmitting structure4400, and the third torque-transmitting structure4600. The second torque-transmitting structure4400is provided to the second bicycle inbound facing surface4000. The third torque-transmitting structure4600is configured to engage with the first torque-transmitting structure1800in the state where the bicycle rear sprocket assembly1000is mounted to the bicycle rear hub assembly.

(4) The second sprocket3800has the second total tooth number that is larger than the first total tooth number. Specifically, the first total tooth number is equal to or smaller than ten and the second total tooth number is eleven or more than eleven.

(5) The second torque-transmitting structure4400is configured to engage with the torque-transmitting structure400sprovided to the sprocket support portion400of the bicycle rear hub assembly1000in the state where the bicycle rear sprocket assembly1000is mounted to the bicycle rear hub assembly1000.

(6) The second torque-transmitting structure4400includes a plurality of second splines4400s.

The shortcomings of the second sprocket3800of the US124 are:

A separation ring3801is located between the second torque-transmitting structure4400and the third torque-transmitting structure4600. The separation ring3801includes an opening3802which has a diameter D400. The diameter D400is equal to the diameter D100of the first opening2400of the first sprocket1200. The second torque-transmitting structure4400is engaged with the torque-transmitting structure400sof the sprocket support portion400. The third torque-transmitting structure4600is configured to engage with the first torque-transmitting structure1800. The separation ring3801is located between the first torque-transmitting structure1800and the sprocket support portion400. Obviously, the separation ring3801occupies the connection area between the second torque-transmitting structure4400and the torque-transmitting structure400s. The separation ring3801also occupies the connection area between the third torque-transmitting structure4600and the first torque-transmitting structure1800. This results in unstable connection between the second sprocket3800, the sprocket support portion400and the first sprocket1200.

US124 adopts the following three options to improve the unstable connection problem and to meet the regulation regarding the gap between sprockets.

(1) The second sprocket3800includes a protrusion5000to increase the connection area between the second torque-transmitting structure4400and the torque-transmitting structure400s.

(2) The third sprocket5200includes a stepped recess5400formed to the surface5800of the third sprocket5200. The recess5400accommodates the protrusion5000.

(3) The depth of the third torque-transmitting structure4600is increased to increase the connection area between the third torque-transmitting structure4600and the first torque-transmitting structure1800.

However, the above mentioned options increase the manufacturing cost due to difficult machining the metal-made torque-transmitting structures4400,4600s.

The present invention is intended to change the minimum number of teeth of the smallest cog so as to increase the tooth ratio and keeping it compatible with the existing chainrings.

SUMMARY OF THE INVENTION

The present invention relates to a bicycle derailleur cassette with increased tooth ratio, which comprises a driver body connected to a rear hub. Multiple cogs are sequentially mounted to the driver body with equal spacing. The least number of the teeth among the cassette is eleven. An additional cog is mounted to the driver body and located opposite to the rear hub. The additional cog has 8-10 teeth.

The functions of the technical character of the present invention are that:

The advantages of the present invention are that the present invention adds an additional cog to the existing bicycle cassette and the added cog has a teeth number less than eleven, preferably 10. The tooth ratio is increased by the additional cog and the chainring to break through the limitation of tooth ratio of existing bicycle and to increase the gears of the bicycle cassette.

The additional cog is compatible with the existing driver body so that no change is needed of the existing driver body.

The additional cog is connected to the driver body and spaced from the next cog so that the chain is able to smoothly switch between the cogs.

The second technical characters of the present invention are that:

A bicycle derailleur cassette with increased tooth ratio comprises a driver body connected to a rear hub of a bicycle. A plurality of cogs are sequentially mounted to the driver body with equal spacing. The plurality of cogs include a second cog. The driver body has a first end and a second end opposite to the first end. The first end of the driver body is connected to the rear hub. A first cog is mounted to the second end of the driver body. A threaded ring is located in the second end of the driver body. An additional cog has at least one tooth less than the number of teeth of the first cog. The additional cog has an annular lip extending axially from the rear end thereof. Multiple second protrusions and multiple second recesses are axially and alternatively formed in the annular lip. A ring-shaped cap has a tubular portion extending axially therefrom. The tubular portion extends through the additional cog and is fixed to the threaded ring. The ring-shaped cap is located at one side of the additional cog. The first cog includes:

multiple cog teeth, a sprocket, a flange, multiple engaging portions, multiple first protrusions and multiple first recesses.

The total number of the multiple cog teeth is eleven or more than eleven.

The sprocket includes an inside that faces the axial center axis of rear hub, and an outside is located opposite to the inside. The inside of the sprocket forms the flange in the axial direction. The flange forms the multiple engaging portions facing the driver body. The outside of the sprocket forms the first protrusions and the first recesses facing the driver body.

The engaging portions include a first axial length formed axially of the engaging portion. The engaging portions are connected to multiple keys of the driver body.

The first protrusions and the first recesses include a second axial length formed axially thereof. The second axial length is equal to a difference of the axial length of sprocket and the first axial length. The multiple first protrusions and the first recesses are engaged with the second recesses and the second protrusions of the additional cog.

The functions of the second technical characters of the present invention are that:

The axial length of the sprocket is fully used for the connection between the driver body and the additional cog. Under the restrictions of the sprocket pitch and the thickness of the cogs, the present invention provides the maximum connection area between the first cog and the driver body and the additional cog.

The third technical characters of the present invention are that:

The axial length of the flange is equal to the sprocket pitch between the first cog and the second cog. The flange contacts the second cog.

The functions of the third technical characters of the present invention are that:

When the first cog is engaged with the driver body, the sprocket pitch between the first cog and the second cog meets the regulation.

The fourth technical characters of the present invention are that:

The first cog includes a contact face. The contact face is located at a conjunction area between the engaging portions and the first recesses and the first protrusions. The contact face contacts the second end of the driver body.

The functions of the fourth technical characters of the present invention are that:

The center axis of the first cog is perpendicular to the axis of the sprocket assembly.

The fifth technical characters of the present invention are that:

The second protrusions of the additional cog contact the end face of the threaded ring.

The functions of the fifth technical characters of the present invention are that:

The center axis of the additional cog is perpendicular to the axis of the sprocket assembly. The sprocket pitch between the additional cog and the first cog meets the regulation.

The present invention will become more obvious from the following description when taken in conjunction with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIGS.4and5, the bicycle cassette of the present invention comprises a driver body10having a first end11and a second end12located opposite to the first end11. The first end11of the driver body10is connected to the rear hub (not shown). An additional cog40having ten teeth is connected to the second end12of the driver body10. Multiple cogs13-18(i.e.13,14,15,16,17and18) are sequentially mounted to the driver body10with equal spacing in order of increasing number of teeth from the second end12towards the first end11. The inside of the driver body10is well known in the art and will not be described here.

The bicycle cassette of the present invention achieves an increased tooth ratio compared to conventional bicycle cassette.

The driver body10comprises a first threaded portion121defined in the inner periphery of the second end12of the driver body10.

A threaded ring30has a second threaded portion31defined in the outer periphery thereof, and the first threaded portion121is threadedly connected to the second threaded portion31of the threaded ring30to connect the threaded ring30to the inner periphery of the second end12of the driver body10. The threaded ring30includes a third threaded portion32defined in the inner periphery thereof. The threaded ring30is used to reduce the inner diameter of the driver body10.

As shown inFIGS.6and7, a first cog20has eleven or more than eleven teeth and includes an annular flange21extending from the rear end thereof. The flange21includes an engaging portion22in the form of ridge-recess defined in the inner periphery thereof so as to be engaged with the outer periphery of the driver body10. The flange21is connected to the outer periphery of the second end12of the driver body10. Multiple first protrusions23and multiple first recesses24are radially and alternatively formed in the inner periphery of the first cog20. The first protrusions23contact the second end12of the driver boy10and the outer face of the threaded ring30.

As shown inFIGS.8and9, the additional cog40has at least one tooth less than the number of teeth of the first cog20. Preferably, the additional cog40has 8 to 10 teeth. The additional cog40has an annular lip41extending axially from the rear end thereof, and multiple second protrusions42and multiple second recesses43are axially and alternatively formed in the annular lip41. The second protrusions42of the additional cog40are engaged with the first recesses24of the first cog20, and the first protrusions23of the first cog20are engaged with the second recesses43of the additional cog40, such that the additional cog40is engaged with the first cog20and located outside of the second end12of the driver body10. By the annular lip41, the additional cog40is spaced from the first cog20properly to meet the needs for switching of the chain.

As shown inFIGS.10to13, a cap50is a ring-shaped cap and has a tubular portion51extending axially from the rear end thereof. The tubular portion51extends through the additional cog40and includes a fourth threaded portion52defined in the outer periphery thereof. The fourth threaded portion52is located close to the distal end of the tubular portion51. The fourth threaded portion52of the tubular portion51is threadedly connected to the third threaded portion32of the threaded ring30. The cap50is located at one side of the additional cog40to position all of the cogs13-18to the driver body10. The additional cog40includes a first anti-slip terrain44formed on one side thereof, and the cap50includes a second anti-slip terrain54formed on one side thereof. The first anti-slip terrain44and the second anti-slip terrain54are engaged with each other.

As shown inFIGS.10to13, the present invention adds the additional cog40which has less than 11 teeth (preferably ten teeth) to the driver body10of the existing bicycle cassette to increase the tooth ratio to break through the limitation of tooth ratio of existing bicycle cassettes. The number of teeth of the additional cog40depends on the number of teeth of the first cog20, preferably, one or two teeth less than the number of teeth of the first cog20. In this embodiment the smallest cog of the cassette has 11 teeth, so that the additional cog40has 10 teeth.

Take the road bicycles with an eighteen-gear derailleur system as an example, the system includes a 50/34 T compact crankset. After the additional cog40is added, the tooth ratio is increased and the derailleur system becomes a twenty-gear derailleur system. The tooth ratio is illustrated as follows:

The technical characters are revealed to the first cog20.

As shown inFIGS.6and7, the first cog20includes multiple cog teeth201, a sprocket25, a flange21, multiple engaging portions22, multiple first protrusions23and multiple first recesses24.

The total number of the multiple cog teeth201is eleven or more than eleven.

As shown inFIGS.12to16, the sprocket25including an inside251that faces the axial center axis of rear hub CL, and an outside252located opposite to the inside251and located at the axial direction Da. The inside251of the sprocket25forms the flange21in the axial direction Da. The flange21forms the multiple engaging portions22facing the driver body10. The outside252of the sprocket25forming the first protrusions23and the first recesses24in the axial direction Da. The axial length of the flange21in the axial direction Da is equal to the sprocket pitch P1between the first cog20and the second cog18. The sprocket pitch P1between the first cog20and the second cog18meets the regulation.

The engaging portions22are connected to multiple keys101of the driver body10.

As shown inFIGS.16and20, the engaging portions33includes a first axial length L1in the axial direction Da. The first axial length L1is greater than the sprocket pitch P1. That is to say, when the first cog20is engaged with the driver body10, the first axial length L1of the multiple engaging portions22and the driver body10is greater than the sprocket pitch P1. Under the restriction of the sprocket pitch P1, the connection area between the first cog20and the driver body10is increased.

As shown inFIGS.12to18, the first protrusions12and the first recesses24are engaged with the second recesses43and the second protrusions42of the additional cog40. The first protrusions23and the first recesses24include a second axial length L2in the axial direction Da. The second axial length L2is equal to a difference of the axial length of sprocket L and the first axial length L1in the axial direction Da. In other words, L2=L−L1, that is to say, L=L1+L2. The sum of the first axial length L1and the second axial length L2is equal to the axial length of sprocket L in the axial direction Da. That is to say, the axial length of sprocket L in the axial direction Da is fully used to the connection between the driver body10and the additional cog40, and creates a maximum connection area.

As shown inFIGS.16,19and20, the first cog20includes a contact face27, and the contact face27is located at a conjunction area between the engaging portions22and the first recesses24and the first protrusions23. The first cog20is engaged with the driver body10by the multiple engaging portions22. The contact face27contacts the second end12of the driver body10so as to define that the center axis of first cog CL2is perpendicular to the axis of sprocket assembly Ax. The first cog20is engaged with the driver body10, and the flange21contacts the second cog18. Therefore, the sprocket pitch P1between the first cog20and the second cog18meets the regulation. The second recesses43and the second protrusions42of the additional cog40are engaged with the first protrusions23and the first recesses24of the first cog20. The second protrusions42of the additional cog40contact the end face of the threaded ring30. Therefore, the center axis of additional cog CL3is perpendicular to the axis of sprocket assembly Ax, and the sprocket pitch P2between the additional cog40and the first cog20meets the regulation.