GEAR CHANGE SYSTEM FOR CYCLE
The gear change system addresses chain flex and stress issues in bicycle gear-shifting by using a movable shaft and toothed discs with translationally movable arms and cams for smooth, torque-preserving gear transitions.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- SAVARD FRANCK
- Filing Date
- 2024-11-22
- Publication Date
- 2026-05-29
AI Technical Summary
Existing bicycle gear-shifting systems cause chain flex and stress during lateral movement, leading to creaking and destructive derailments, especially during gear changes under load.
A gear change system with a movable shaft and toothed discs that allow speed changes without lateral chain movement, using a displacement system with translationally movable gear-shifting arms and rotationally movable cams to move toothed angular sectors between rest and active positions, along with locking and guiding mechanisms to ensure smooth transitions.
The system prevents chain bending and maintains constant effort during gear changes, eliminating creaking and derailments by ensuring seamless transitions between toothed discs without interrupting torque.
Smart Images
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Abstract
Description
Title of the invention: SYSTEM OF GEAR CHANGE FOR CYCLE technical field
[0001] The present invention relates to a gear-changing system, in particular for a cycle, and to a cycle comprising such a gear-changing system. PRIOR TECHNOLOGY
[0002] A bicycle typically includes a chain mounted between a chainring at the front and a sprocket at the rear. To assist the cyclist, the bicycle typically includes a gear-shifting system with a rear derailleur and a front derailleur. Each derailleur allows the cyclist to select a chainring and a sprocket suited to the desired effort level.
[0003] To this end, the cycle comprises several chainrings (which, in the context of this document, are referred to as toothed discs) at the level of the crankset and sprockets at the level of the rear wheel, which are arranged coaxially next to each other. Each derailleur ensures the lateral movement of the chain from one chainring, or sprocket, to the adjacent chainring, or sprocket.
[0004] Even if such derailleurs perform satisfactorily, they generate chain flex during lateral movement, creating stress on the chain, which in turn causes creaking, or even unexpected and destructive derailments of the derailleur and chain. These problems occur particularly during gear changes under load (i.e., when force is applied to the crankset and chain during a gear change). Description of the invention
[0005] An object of the present invention is thus to propose a gear change system in particular for cycle without interruption of torque and without lateral movement of the chain.
[0006] To this end, a speed change system for a chain is proposed, said speed change system comprising:
[0007] - a movable shaft rotating around a pedaling axis,
[0008] - a first toothed disc inscribed in a working plane, integral with said shaft and designed to mesh with the chain,
[0009] - at least one other toothed disk divided into at least two toothed angular sectors, where each toothed angular sector is movable in translation between a rest position in which said toothed angular sector is offset relative to the working plane and an active position in which said toothed angular sector is in the working plane, and
[0010] - a displacement system arranged to move each toothed angular sector of from the resting position to the active position and vice versa.
[0011] Advantageously, for each other toothed disc, the displacement system comprises a translationally movable gear-shifting arm, a rotationally movable cam having a cam track where a proximal end of the gear-shifting arm is guided by the cam track, and each toothed angular sector of said other toothed disc comprises first actuation means which cooperate with a distal end of the gear-shifting arm to move said toothed angular sector from the rest position to the active position and second actuation means which cooperate with the distal end of the gear-shifting arm to move said toothed angular sector from the active position to the rest position.
[0012] Advantageously, for each toothed angular sector, the gear change system includes locking means arranged to lock said toothed angular sector alternately in the active position and the rest position.
[0013] Advantageously, the gear change system comprises a cage fixed to the shaft, divided into sectors in which toothed angular sectors are mounted, and for each sector, the cage comprises first guiding means cooperating with second guiding means of the toothed angular sectors to achieve a sliding connection.
[0014] Advantageously, for each toothed angular sector, the locking means consist of a ball mounted on a spring in a housing of the toothed angular sector and for each position, a recess in the cage into which the ball is inserted in the corresponding position.
[0015] Advantageously, the system includes a cam having an indexing notch and a groove serving as an extreme stop.
[0016] Advantageously, the system includes a third roller allowing a free zone for chain engagement to be opened, to allow a speed change in all situations.
[0017] Advantageously, the system includes ad hoc conjugate zones between the toothed angular sectors, allowing a force between the crank axle and the chain to be transmitted directly from one toothed disc to another.
[0018] The invention also proposes a cycle comprising a speed change system according to one of the preceding variants and a chain mounted in the worktable and meshing with the first toothed disc where the passage from the active position to the rest position and vice versa takes place in an angular sector delimited between two strands of the chain where the chain does not mesh with the first toothed disc.
[0019] Advantageously, the cycle includes a tensioning system arranged to put the chain under tension. Brief description of the drawings
[0020] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which:
[0021] [Fig-1] is a perspective view of a cycle drive system comprising a gear-changing system according to the invention,
[0022] [Fig.2] is a side view of the drive system of the [Fig.1] without the cover,
[0023] [Fig.3] is a perspective view of the gear-changing system according to the invention,
[0024] [Fig.4] is a perspective view of the gear-changing system according to the invention,
[0025] [Fig.5] is a perspective view of a detail of the gear shift system according to the invention,
[0026] [Fig.6] is a perspective view of the detail of [Fig.5] seen from another angle,
[0027] [Fig.7] is a perspective view of a toothed slide implemented in the gear change system according to the invention,
[0028] [Fig.8] is a perspective view of a detail of the gear-changing system according to the invention,
[0029] [Fig.9] is a side view of a first cam implemented in the system of speed change according to the invention,
[0030] [Fig. 10] is a side view of a second cam implemented in the gear-changing system according to the invention,
[0031] [Fig. 11] is a side view of a third cam implemented in the gear-changing system according to the invention,
[0032] [Fig. 12] is a side view of a fourth cam implemented in the gear-changing system according to the invention,
[0033] [Fig. 13] is a perspective view of a guidance system for a gear shift arm,
[0034] [Fig. 14] is a section by a plane perpendicular to a pedaling axis of the gear-changing system according to the invention,
[0035] [Fig. 15] is a perspective view of an embodiment of a gear change system.
[0036] DETAILED STATEMENT OF IMPROVEMENTS
[0037] Figure 1 shows a gear-changing system 100 according to the invention, implemented, for example, in a bicycle. Such a gear-changing system 100 can be implemented in all types of systems comprising gears driven in rotation by a driving force (engine, muscle) and driving a chain, or driven by a chain. The gear-changing system 100 is particularly suited to vehicles with internal combustion engines, electric motors, or muscle power, such as bicycles, electric bicycles, etc.
[0038] The invention will be described more particularly in the case of a cycle, but it applies in the same way to other systems where it can be implemented.
[0039] Figure 2 shows the gear-changing system 100 without a protective cover.
[0040] Conventionally, a bicycle comprises a frame on which a front wheel and a rear wheel are mounted as rotating parts. Arrow F indicates the direction of travel of the bicycle. The bicycle has a rear hub 12 in which a rear axle is mounted, which is integral with the rear wheel. The hub also carries a rear sprocket onto which a chain 10 meshes. In the embodiment of the invention presented here, the chain 10 is enclosed in a chain guard 14.
[0041] Similarly, the gear shifting system 100 includes a chassis 16 which is fixed to the frame of the cycle for example by screws and which here takes the form of a protective casing in which the mechanism of the gear shifting system 100 is enclosed.
[0042] The cycle includes a shaft 102 mounted to rotate freely on the frame around a pedaling axle X. The shaft 102 is equipped with two cranks 18, each equipped with a pedal 20. Conventionally, the actuation of the pedals 20 drives the cranks 18, which rotates the shaft 102. The shaft 102 can also be the shaft of a motor, for example an electric motor.
[0043] In the embodiment of the invention presented here, the gear-shifting system 100 is installed at the chainrings 104 and 106a-d, but it can also be installed at the sprockets, either as a complement or as a replacement. Thus, according to a particular arrangement, the gear-shifting system 11 can be installed at the sprockets using an additional system for synchronizing gear changes at the crankset with another gear shift located on an intermediate shaft or on a rear wheel axle.
[0044] In the following description, a chainring, whether sectored or not, is called a "toothed disc" when it is at the level of the pedals, or a sprocket when it is at the rear or when it is coupled to a secondary shaft in a box interposed between the crankset and the rear wheel.
[0045] Figs. 3 and 4 show the gear change system 100 at two opposite angles.
[0046] The gear change system 100 thus comprises the shaft 102 and a first toothed disc 104. The first toothed disc 104 is inscribed in a working plane P which is perpendicular to the pedaling axis X. The working plane P is the plane in which the chain 10 moves.
[0047] The first toothed disc 104 is fixed to the shaft 102 and meshes with the chain 10. Thus, the rotation of the shaft 102 causes the chain to move, which in turn drives the rotating sprocket and, consequently, the rear wheel. According to a particular arrangement, the sprocket has a freewheel mechanism.
[0048] The gear-changing system 100 also includes at least one other toothed disc 106a-d, here four in number, for a five-platter cycle. Each other toothed disc 106a-d has a diameter greater than the diameter of the first toothed disc 104, and the diameters of the other toothed discs 106a-d are all different so that toothed discs 104 and 106a-d are arranged one inside the other in a nested arrangement.
[0049] Each other toothed disc 106a-d is divided into at least two toothed angular sectors 108a-e, here five in number. Each toothed angular sector 108a-e has teeth 109 on its periphery which cooperate with the chain 10. Preferably, all the toothed angular sectors 108a-e have the same angular extent, here 72°, and the same number of teeth.
[0050] Each toothed angular sector 108a-e is centered on the pedaling axis X and is linked to the shaft 102 so as to rotate with it. There are thus n*N toothed angular sectors 108a-e, where n is the number of toothed angular sectors 108a-e per other toothed disk 106a-d and N is the number of other toothed disks 106a-d. Preferably, there is the same number of toothed angular sectors 108a-e for each other toothed disk 106a-d, and the toothed angular sectors 108a-e are aligned concentrically around the pedaling axis X (except during the lateral movement of each angular sector).
[0051] Each toothed angular sector 108a-e is movable in translation between a rest position in which the toothed angular sector 108a-e is offset from the working plane P and an active position (106c, [Fig. 5]) in which the toothed angular sector 108a-e is in the working plane P. The displacement from the rest position to the active position is shown here by the arrows D in Figs. 3 and 4. The direction of the translation is parallel to the pedaling axis X.
[0052] In the rest position, the toothed angular sector 108a-e is off the working plane P and the teeth 109 do not mesh with the chain 10. In the active position, the toothed angular sector 108a-e is in the working plane P and the teeth 109 mesh with the chain 10.
[0053] The gear change system 100 also includes a displacement system 150 which moves each toothed angular sector 108a-e from the rest position to the active position and vice versa. Upon reaching the active position, the toothed angular sector 108a-e will then mesh (in its rotation) with the chain 10. To facilitate the entry of the chain 10 onto the toothed angular sector 108a-e, at least the first tooth of said toothed angular sector 108a-e may have a different profile (more pointed or more rounded or beveled or concave, for example).
[0054] Thus, when the cycle operator wants to change toothed discs 104, 106a-d, i.e., speed, they actuate the displacement system 150, which will successively move, within the gap between the chain, each toothed angular sector 108a-e of the toothed disc 106a-d to be moved. Depending on the case, these toothed angular sectors 108a-e will move from the rest position to the active position or vice versa. The operator will actuate the displacement system 150 as many times as necessary in one direction or the other to place the desired toothed disc 104, 106a-d in the meshing position with the chain 10.
[0055] Starting from the first toothed disc 104, the displacement system 150 gradually moves the other toothed discs 106a-d from the rest position to the active position by moving from the smallest diameters to the largest diameters, and vice versa for the passage from the active position to the rest position.
[0056] As the gear change takes place at the level of the plane of the chain 10, the latter is not bent and the disadvantages of the prior art are avoided and the efforts provided by the driver are constant.
[0057] The actuation of the movement system 150 is carried out for example from the handlebar by actuation of a rotating handle or others through cables 22a-b which join the movement system 150. According to other arrangements, the movement system 150 can also be operated electrically by an automated system or by a user.
[0058] Figs. 7 to 14 show a particular embodiment of the displacement system 150.
[0059] Here there is an upward cable 22a which ensures the passage from the rest position to the active position and a downward cable 22b which ensures the passage from the active position to the rest position.
[0060] For each other toothed disc 106a-d, the displacement system 150 includes a gear-shifting arm 152. Each gear-shifting arm 152 is mounted to move in translation, here parallel to the pedaling axis X. To this end, Each gear shift arm 152 is mounted to slide in a fixed tunnel 17 and integrated here into the chassis 16.
[0061] For each other toothed disc 106a-d, the displacement system 150 also includes a cam 154 which is mounted to rotate freely about an actuation axis X' which is here perpendicular to the pedaling axis X. The cams 154 are mounted fixed and coaxially on a shaft 153 which is mounted on the frame 16 and which is rotatable about the actuation axis X'.
[0062] The cables 22a-b are fixed to the shaft 153 in such a way that the pulling of one cable 22a causes the shaft 153 to rotate in a first direction corresponding to the passage from the rest position to the active position, and in such a way that the pulling of the other cable 22b causes the shaft 153 to rotate in a second direction corresponding to the passage from the active position to the rest position.
[0063] Each cam 154 has a cam track 154a. In the embodiment of the invention presented here, there is the same cam 154 for two of the other toothed discs 106a-d, and a cam track 154a is formed on each face of said same cam 154. According to an embodiment not shown, the cam 154 may be provided with notches allowing precise indexing of each speed. Said notches then cooperate with an indexing finger actuated by a spring.
[0064] Each gear shift arm 152 has a proximal end and a distal end. The proximal end of the gear shift arm 152 is guided by the cam track 154a and here takes the form of a movable bearing rotating about an axis parallel to the actuation axis X'.
[0065] Each toothed angular sector 108a-e of each other toothed disc 106a-d has on a cylindrical face coaxial with the pedaling axis X, first actuation means 156a and second actuation means 156b. Here, the actuation means 156a-b take the form of a boss on said toothed angular sector 108a-e.
[0066] The distal end of the gear-shifting arm 152 cooperates with the actuation means 156a-b to move the relevant toothed angular sector 108a-e, where the first actuation means 156a ensure the transition from the rest position to the active position and the second actuation means 156b ensure the transition from the active position to the rest position. The distal end also takes the form of a movable bearing rotating about an axis parallel to the actuation axis X'.
[0067] Thus, when the cam track 154a moves the proximal end (arrow +, [Fig. 8], corresponding to arrow D), the distal end moves and as the toothed angular sector 108a-e rotates, the first actuating means 156a meet the distal end and the shape of the first actuating means 156a causes the displacement of the angular sector 108a-e towards the active position. Conversely, when the cam path 154a moves the proximal end (arrow -, [Fig.8]), the distal end moves and as the toothed angular sector 108a-e rotates, the second actuating means 156b meet the distal end and the shape of the second actuating means 156b causes the angular sector 108a-e to move towards the rest position.
[0068] As shown in Figs. 9 to 12, each cam track 154a is different so as to trigger the movement of the different gearshift levers 152 in a synchronized manner. The movement of the gearshift arm 152 occurs at the point where the orientation of the cam track 154a changes. The outer circular portion 153a and the inner circular portion 153b correspond to a non-movement of the gearshift arm 152. The intermediate portion 153c between the outer circular portion 153a and the inner circular portion 153b corresponds to the portion of the cam track 154a that moves the gearshift arm 152 in one direction or the other depending on the direction of rotation of the cam 154.
[0069] In the embodiment of the invention shown in [Fig. 8], when the gear shift arm 152 is moved in the + direction, the distal end rolls against the track 156c until the first actuation means 156a arrive, which moves the toothed angular sector 108a-e. By successive passage of the different toothed angular sectors 108a-e constituting another toothed disc 106a-d, said toothed angular sectors 108a-e will position themselves one after the other in the active position or in the rest position.
[0070] Each actuation means 156a-b here takes the form of a ramp.
[0071] To ensure locking in the rest position and in the active position, for each toothed angular sector 108a-e, the gear change system 100 includes locking means 170. These locking means 170 are arranged so as to lock the toothed angular sector 108a-e alternately in the active position and the rest position while allowing the release of the toothed angular sector 108a-e when reverse movement is desired.
[0072] To ensure proper guidance and alignment of the toothed angular sectors 108a-e, the gear change system 100 includes a cage 160 which is fixed to the shaft 102. The cage 160 is divided into sectors 160a-e, and in each sector 160a-e, the toothed angular sectors 108a-e of the same rank of the other toothed discs 106a-d are mounted to slide. Thus, in each sector 160a-e, a toothed angular sector 108a-e of each of the other toothed discs 106a-d is arranged, and since the cage 160 is fixed to the shaft 102, the rotation of the latter causes the rotation of the toothed angular sectors 108a-e.
[0073] For each sector 160a-e, the cage 160 comprises, for each toothed angular sector 108a-e arranged in said sector 160a-e, first guiding means 162 which cooperate with second guiding means 164 which said toothed angular sectors 108a-e comprise to achieve a sliding connection between the guiding means 162 and 164.
[0074] The first guiding means 162 here take the form of ribs and the second guiding means 164 here take the form of grooves in each of which a rib is mounted to slide.
[0075] According to a particular embodiment shown in [Fig. 14], the locking means 170 consist of a ball 170a which is movably mounted in a housing 170d of the toothed angular sector 108a-e considered. The housing 170d is blind and designed to lock the ball 170a so that it cannot exit the housing 170d, for example by fitting a collar with a diameter smaller than the diameter of the ball 170a at the opening of the housing 170d.
[0076] The locking means 170 also include a spring 170b on which the ball 170a is mounted and which ensures the push of the ball 170a towards the opening of the housing 170d i.e. towards an exit of the ball 170a from the housing 170d.
[0077] For each position, i.e. for the active position and the rest position, the locking means 170 include a recess 170c which is formed on the cage 160 where the recess 170c is arranged so that the ball 170a is inserted into it when the corresponding position is reached by the corresponding toothed angular sector 108a-e.
[0078] To prevent the toothed angular sectors 108a-e from pushing or pulling on the chain 10 during gear changes, the transition from the active position to the rest position and vice versa takes place in an angular sector 180 around the pedaling axis X which is delimited between the two strands of the chain 10 on the side where the chain 10 does not mesh with the first toothed disc 104 or the other toothed discs 106a-d, i.e. outside the winding zone of the chain 10 (i.e. the chain gap).
[0079] To ensure good tension of the chain 10 when it changes toothed disc 104, 106a-d, the cycle includes a tensioning system 190 which is arranged to put the chain 10 under tension.
[0080] In the embodiment of the invention presented in particular in Figs. 3 and 4, the tensioning system 190 comprises a swing arm 192 which is here fixed to the chassis 16 by means of a screw 194.
[0081] The oscillating arm l92 is mounted to rotate freely around a tilting axis X' ' perpendicular to the working plane P.
[0082] Each end of the swing arm 192 is equipped with a toothed roller 196a-b movable in rotation around an axis parallel to the tilting axis X”, where the chain 10 passes between the toothed rollers 196a-b and meshes with each of them.
[0083] The tensioning system 190 also includes a return element 198, here a torsion spring, which forces the lever 192 to rotate so as to tension the chain 10.
[0084] According to a particular arrangement, a third roller 196c allows a free engagement zone of the chain 10 to be opened to allow a change of speed in all situations.
[0085] According to another particular arrangement shown in [Fig. 15], the system includes a cam 154 having indexing notches 300 and a groove 310 serving as an extreme stop by cooperating with a stop screw.
[0086] According to another particular arrangement, the system includes ad hoc conjugate zones 108f between the toothed angular sectors 108a-e, allowing a force between the bottom bracket axle 102 and the chain 10 to be transmitted directly from one toothed disc to another. In other words, according to this arrangement, the transmission of force occurs radially from the outside to the inside without the forces being transmitted to the chainring arms.
Claims
Demands
1. A gear-shifting system (100) for a chain (10) or a belt, said gear-shifting system (100) comprising: - a shaft (102) rotatable about a pedal axis (X), - a first toothed disc (104) inscribed in a working plane (P), integral with said shaft (102) and intended to mesh with the chain (10), - at least one other toothed disc (106a-d) divided into at least two toothed angular sectors (108a-e), wherein each toothed angular sector (108a-e) is movable in translation between a rest position in which said toothed angular sector (108a-e) is offset from the working plane (P) and an active position in which said toothed angular sector (108a-e) is in the working plane (P), and - a displacement system (150) arranged to move each angular sector toothed (108a-e) from the rest position to the active position and vice versa.
2. A gear shifting system (100) according to claim 1, characterized in that for each other toothed disc (106a-d), the shifting system (150) comprises a gear shifting arm (152) movable in translation, a cam (154) movable in rotation and having a cam track (154a) where a proximal end of the gear shifting arm (152) is guided by the cam track (154a), and in that each toothed angular sector (108a-e) of said other toothed disc (106a-d) comprises first actuating means (156a) which cooperate with a distal end of the gear shifting arm (152) to move said toothed angular sector (108a-e) from the rest position to the active position and second actuating means (156b) which cooperate with the distal end of the gear shifting arm (152) to move said toothed angular sector (108a-e) from active position to rest position.
3. Gear change system (100) according to any one of claims 1 or 2, characterized in that, for each toothed angular sector (108a-e), the gear change system (100) comprises locking means (170) arranged to lock said toothed angular sector (108a-e) alternately in the active position and the rest position.
4. Gear change system (100) according to any one of claims 1 to 3, characterized in that it comprises a cage (160) integral with the shaft (102), divided into sectors (160a-e) in which toothed angular sectors (108a-e) are mounted, and in that for each sector (160a-e), the cage (160) comprises first guiding means (162) cooperating with second guiding means (164) of the toothed angular sectors (108a-e) to achieve a sliding connection.
5. Gear change system (100) according to claim 4 when it depends on claim 3, characterized in that for each toothed angular sector (108a-e), the locking means (170) consist of a ball (170a) mounted on a spring (170b) in a housing (170d) of the toothed angular sector (108a-e) and for each position, a recess (170c) of the cage (160) into which the ball (170a) is inserted in the corresponding position.
6. Gear change system (100) according to any one of the preceding claims, comprising a cam (154) having an indexing notch (300) and a groove (310) serving as an extreme stop.
7. Gear change system (100) according to any one of the preceding claims, a third roller 196c allowing a free engagement zone of the chain 10 to be opened, to allow a gear change in all situations.
8. Gear shifting system (100) according to any one of the preceding claims, comprising ad hoc conjugate zones (108f) between the toothed angular sectors (108a-e), allowing a force between the bottom bracket axle (102) and the chain (10) to be transmitted directly from one toothed disc to another.
9. Cycle comprising a speed change system (100) according to any one of claims 1 to 8 and a chain (10) mounted in the work plane (P) and meshing with the first toothed disc (104) where the passage from the active position to the rest position and vice versa takes place in an angular sector (180) delimited between two strands of the chain (10) where the chain (10) does not mesh with the first toothed disc (104).
10. Cycle according to claim 9, characterized in that it comprises a tensioning system (190) arranged to put the chain (10) under tension.