FR2496587A1 - Speed-change mechanism for multi-sprocket bicycle gearing - uses cam to actuate movable member of changeover frame to shift chain between sprockets - Google Patents

Abstract

A fitting (7) is secured to the frame of a bicycle. A parallel linkage has an outside link (16) and an inside link (9) whose one ends are pivotally connected (17,12) to the fitting. A movable member (25) pivotally connected to the opposite ends of the links has a changeover frame (33) rotatably secured to it. The changeover frame carries a guide wheel and a chain tension wheel. A cam engages the movable member to change the position of the changeover frame and shift the chain to the desired step of a multi-step sprocket assembly. The spring-biased cam (18) is mounted on a shaft (17) connecting the outside link to the bicycle fitting, and rotates together with a wire-operated reel coaxially mounted on the shaft. Rotation of the cam actuates the parallel linkage through a lever (11) pivotally carried by a shaft (12) connecting the inside link to the fitting.

Description

 The present invention relates to a gear change intended to be mounted on a bicycle fitted with a pinion with several teeth, this gear change makes it possible to pass the chain of the bicycle over the selected teeth of the pinion.

 The inventors described a gear change intended to be mounted on a bicycle in the Japanese patent application No. 90 492/75 which was put to public inspection under No. 15 033/77. The gear change described in this application has drawbacks in that, in addition to the axes used to maintain a system of parallel links, a separate axis is fixed on a mounting member to keep a gear change control cam in rotation, a reel connected to a control cable and a spring, so that this gear change is of complicated and comparatively heavy construction and further comprises an adjustment screw projecting towards the outside of the bicycle so that it risks injuring a person in the immediate vicinity and therefore constitutes a danger.

 Ea consequence, an object of the present invention is to eliminate the drawbacks associated with the prior art. The present invention makes it possible to simplify the construction of a gear change intended to be mounted on a bicycle and to reduce the weight of the latter, by mounting a gear change control cam, a reel connected to a control cable and elastic means on pivoting axes of a system C parallel rods.

 Another object of the present invention is to improve the safety of bicycles provided with a gear change mounted protruding thereon, by enclosing the elements, exposed in the devices of the prior art, namely the change control cam gears, springs, adjustment screws, a movable member and the like, in an envelope and an external link in order to eliminate the projections extending towards the outside of the bicycle.

An embodiment of the present invention is described below by way of example, with reference to the accompanying drawings in which
- Figure 1 is a schematic side view of a gear change according to the present invention, mounted on the axis of the rear hub of the bicycle;
- Figure 2 is a schematic front view of the gear change of Figure 1
- Figure 3 is a schematic sectional view along substantially line III-III of Figure 1, showing the internal mechanism thereof;
- Figure 4 is a schematic sectional view along substantially the line IV-TV of Figure 2, the cap being spread to show the inner mechanism;
- Figure 5 is an exploded perspective view of the essential elements of the gear change according to the present invention;
- Figure 6 is a diagram illustrating the outline of a speed change control cam used in the device of the invention; and
- Figures 7 to 9 are sectional views similar to that of Figure 3, showing different operating states of the gear change according to the invention.

 In the various figures of the drawings, 1 is a bicycle frame, 2 is the axis of the rear hub, 3 is a pinion with several teeth, 4 is a chain, 5 is a mounting plate; 6 is a nut, 7 is a metal part, 7 'is a cap, 8 is a bolt, 9 is an internal link, 10, 19, 28 and 35 are coil springs, it is an L-shaped lever, 12 is a mounting rod for the inner link, 13 is an adjusting screw, 14, 26 and 27 are pins, 15 is a follower roller, 16 is an outer link, 17 is a mounting pin for the outer link, 18 is a shift control cam, 20 is a reel, 21 is a stop ring, 22 is a locking pin, 23 is a cable adjuster, 24 is a cable clamp screw, 25 is a movable member, 29 is a guide roller, 30 and 32 are axes, 31 is a tension roller, 33 is a change plate, 34 is a rod, 36 is a stop ring and 37 is a stop pin.

 Referring to Figure 1, there is shown a bicycle frame 1 provided with a rear hub axle 2 carrying a pinion with several teeth 3 with which the chain 4 cooperates selectively. A mounting plate 5 is fixed to this axis 2 by a nut 6 screwed onto a threaded end of the axis.

 In the illustrated embodiment, a metal piece 7 is fixed to the mounting plate 5 by a bolt 8, as seen in Figure 3 and Figure 4. This metal piece 7 is U-shaped and has opposite side walls 7a, 7b and a connecting part 7c situated between them, this connecting part 7c serving to mount the part 7 on the mounting plate 5. The side walls 7a and 7b are pierced with four pin mounting holes, namely two aligned holes 7d intended to receive a pin 12 for mounting an inner link and two aligned holes 7e intended to receive a pin 17 for mounting an outer link. The axis 12 crosses the two holes 7d of the opposite side walls 7a and 7b so as to pivotani the boss 9a of an inner link 9, a helical spring 10 and the boss ila tu'un lever in L it disposed between the side walls of the metal part 7. The inner link 9 comprises, at its upper end, a folded part 9b, an adjusting screw 13 engaging in a tapped hole in the folded part 9b. A locking nut 13a makes it possible to block the adjusting screw 13 with respect to the folded part 9b of the internal link 9. The lower end of the internal link 9 has a channel-shaped part and two aligned holes 9c are provided in the side walls of the channel part for pivoting between these side walls, one side of a movable member 25 by means of a pin 26 passing through the holes 9c, this movable member 25 will be described below. The lever 11 in L comprises, at one end, a folded part 11b, with which the adjusting screw 13 comes into contact.

The opposite end of the lever Il in L carries a follower roller 15 fixed in rotation by a pin 14: The helical spring 10 biases the internal link 9 in a clockwise direction while urging the lever 11 in L in the direction reverse of the watch hands, as seen in FIG. 3. A cap 7 ′ is removably mounted on the metal part 7 so as to close the open outer side of the metal part 7.

 An external link 16 having the shape of a curved channel cooperates with the internal link 9 to produce the system in parallelogram. The outer link 16 comprises side walls 16a and 16b, two aligned holes 16c drilled in the upper end parts of the side walls and intended to receive in rotation the mounting axis 17 of the outer link, two aligned holes 16d drilled in the lower end portions of the side walls and intended to receive a pin 27 supporting the movable member 25 by its side opposite to that carried by the pin 26, and a notch 16e. The axis 17 crosses the aligned holes 7e of the metal part 7 and the holes 16c of the outer link 16, a gear change control cam 18 and a helical spring 18 being rotatably carried by the axis 17 in the space between the side walls 16a, 16b of the outer link 16.

One end of the axis 17 exceeds the metal part 17 and a drum 20 is mounted on this projecting part of the axis 17, as can be seen in FIG. 4 and FIG. 5. With reference to FIG. 5, a stop ring 21 is mounted in an annular groove 17a formed in the projecting end part of the axis 17 to prevent the reel from disengaging from the axis 17.

 As seen in Figure 6, the shift control cam 18 includes portions ai, a2, a3, a4 and a5, separated by portions bl, b2, b3, b4, and b5, the number of the first portions being the same as the number of teeth carried by the pinion 3. The speed change control cam 18 is pierced with a hole 18a and one end of a stop pin 22, integral with the drum 20, s' engages in the hole 18 to secure the cam 18 of the reel 20. One end 19 a of the helical spring 19 is in contact with a pin 18b projecting from the cam 18, as seen in FIGS. 3 and 4, while the the opposite end 19b of the helical spring 19 is in contact with the metal part 7, so that the cam 18 is biased in the direction of the arrow shown in FIG. 3. The notch 16e of the outer link 16, shown in FIG. 5 serves to stop the rotation of the stop pin 22.

 In Figures 1 and 4, there is shown a device 23 for adjusting a cable (not shown) fixed to the metal part 7 and an inner cable (not shown) of a gear change control device (not shown) is wound on the reel 20, one end of this cable being tightened by a screw 24 mounted in a hole 20a of the reel 20.

 As seen in Figures 3, 4, 7 and 8, the upper end of the movable member 25, in the form of a box and surrounded by the outer link 16, is connected to the inner link 9 by the pin 26 passing through the holes 9c of the lower end of the inner link 9. The lower end of the movable member 25 is connected to the outer link 16 by the pin 27 passing through the holes 16d provided at the lower end of the outer link 16 A helicolZdal spring 28 is fitted on the pin 26 to apply a force in the direction of arrow B in FIG. 3 to normally urge the movable member 25 clockwise relative to the internal link 9.

 Referring to Figures 1 and 2, a roller 29 for guiding the chain 4 is pivoted by the change plate 33 via a pin 30 while a tensioner roller 31 for the chain 4 is pivoted by the plate 33 via a pin 32. One end of a rod 34 is fixed to an intermediate portion of the plate 33 and the opposite end of the rod 34 is rotated by a vertical wall 25a of l movable member 25. A helical spring 35 is mounted on the rod 34 between the plate 33 and the vertical wall 25a of the movable member 25. A stop ring 36 is in contact with the end of the rod 34 which protrudes the movable member 25 to prevent the rod from separating therefrom.

A counter plate 33 'is fixed on the change plate 33, at a certain distance from the latter, for carrying the rollers 29 and 31 to rotate between the plate 33 and the counter plate 33'. The helidoldal spring 35 has an extended end 35a which comes into contact with a stop pin 37 fixed on the change plate 33, so that it is biased in the direction of arrow C around the rod 34, as seen in Figure 1.

 We will now describe the operation of the gear change made in accordance with the invention.

When the movable member 25 occupies the position shown in FIG. 2, position corresponding to the highest development, and when a lever (not shown) is acted on to allow the plate 33 to be changed, if traction is exerted on the inner cable of a cable transmission system (not shown) using a control mechanism (not shown), this traction exerted on this screen (not shown) results in the rotation of the reel 20 and the cam 18 over a certain angular distance in the direction of the arrow D in FIG. 3. As a result, the lever 11, in contact with the cam 18, rotates in the direction of the arrow in the figure. The lever 11 can rotate in the direction of the arrow
E relative to the inner link 9 against the elasticity of the spring 10, the latter can only be compressed by a force greater than that necessary to allow the chain 4 to be moved from one to another of the teeth pinion 3. Consequently, as long as the movable member 25 remains movable, the spring 10 will not be compressed. Because the movable member 25 and the change plate 33 are then assumed to be movable, the inner link 9 rotates jointly with the lever 11 from the position shown in Figure 3 to that shown in Figure 7. D, ns this case, the spring 28 is compressed and the outer link 16 rotates with the inner link 9, as seen in the figure 7, so that the movable member 25 moves to a position corresponding to a lower development and the chain is moved to a toothing of the pinion 3 which allows a lower development depending on the angle of rotation of the cam 18 Figure 7 shows the state according to which the chain 4 is moved over the teeth corresponding to the lowest development of the pinion 3.

When the movable member 25 occupies its position corresponding to the lowest development, position shown in FIG. 7, and the lever (not shown) is actuated to move the change plate 33, if the cable transmission system (not shown) is released by the control mechanism (not shown), the reel 20 is rotated by the helical spring 19 to wind the inner cable (not shown). At the same time, the cam 18 rotates over a certain angular distance in the direction of arrow A in figure 7
This rotation of the cam 18 in the direction of the arrow A moves the movable member 25 in a state ready to move and the elasticity of the spring 28 tends to rotate the inner link 9 towards the position corresponding to a higher development and the lever 11 is biased in the direction of the arrow F by the elasticity of the spring 10. Thus, as the cam 18 rotates over a certain angular distance in the direction of the arrow 18 the lever It rotates in the direction of the arrow F of an angular distance which corresponds to the number of differential ranges corresponding to the angle of rotation of the cam 18. It follows that the inner link 9 and the outer link 16 simultaneously leave the position shown in FIG. 7 and move towards the position of FIG. 3. As a result of which the movable member 25 moves towards a position corresponding to a higher development and the chain 4 is moved towards the corresponding toothing of the pinion 3 which allows a develop ement higher than previously by a number of differential ranges corresponding to the angle of rotation of the cam 18.

 By cons, if the lever is in the rest position, the movement of the chain between the teeth adjacent to the pinion 3 is not possible, so that the movable member 25 can not move under these conditions.

Thus, when the movable member occupies a position corresponding to the highest development, position represented in FIG. 3, and the lever (not shown) is in the rest position to prevent the displacement of the movable member 25, if the cable inside of the cable transmission system (not shown) is pulled by the control mechanism (not shown) the reel 20 and the cam 18 are driven simultaneously in rotation in the direction of the arrow D in FIG. 8. that the movable member cannot move, neither the inner link 9 nor the outer link 16 can rotate. The lever 11, however, rotates relative to the inner link 9, following the direction of the arrow
E of the figure against the elasticity of the spring 10, and the follower roller 15 of lever 11 is in contact with the portion of the cam 18 which comes into contact with the follower roller 15 during the rotation of the cam 18 Consequently, the folded part 11b of the lever II serving as a stop moves away from the adjustment screw 13 and occupies a position at a certain distance from it, as can be seen in FIG. 8. Thus, a tensile force rotating the inner link 9 and the outer link 16 to a position corresponding to a lower development is stored by the spring 10. If the lever (not shown) is actuated when this force is stored by the spring 10, the member mobile 25 is allowed to move and the force stored by the spring 10 exceeds that of the spring 28 and forces the inner link 9 and the outer link 16 to rotate until the adjustment screw 13 abuts against the folded part Lever lever 11, as seen in FIG. 9. Consequently, the movable member 25 is moved to a position corresponding to a lower development, and the chalne 4 is moved towards the toothing of the pinion 3 ensuring a lower development than previously a number of differential ranges corresponding to the angle of rotation of the cam 18.

 When the movable member 25 occupies the position shown in FIG. 7 corresponding to the lowest development and the lever (not shown) occupies its rest position preventing the displacement of the movable member 25, if the cable transmission means (not shown) are released by the control mechanism (not shown) the reel 20 winds the inner cable (not shown) thanks to the elasticity of the spring 19 and the cam 18 rotates a certain angular distance in the direction of the arrow Due to the figure. Because the movable member 25 cannot move, neither the internal link 9 nor the external link 16 can rotate. On the other hand, the cam 18 rotates from the position of FIG. 7 to the position of FIG. 9, according to arrow À, and a difference s1 establishes between the cam 18 and the follower roller 15 located at one end of the lever 3t, as shown in FIG. 9 this difference corresponding to the number of differential ranges corresponding to 11 angle of rotation of the cam 18.

 Provided that there is such a gap between the follower roller 15 and the cam 18, if the lever is actuated (not shown) to allow movement of the movable member 25, the elasticity of the spring 28 normally stressing the inner link 9 and the outer link 16 to a position corresponding to a higher development means that the inner link 9, the outer link 16 and the lever II rotate until the follower roller 15 carried by one end of the lever 11 abuts against a portions of the cam 18. As a result, the movable member 25 moves to a position relating to a higher development, as shown in FIG. 3, and the chain 4 is moved towards the teeth of the pinion 3 corresponding to a more higher than previously the number of differential ranges corresponding to the angle of rotation of the cam 18.

 The advantages provided by the present invention will now be described. In gear changes of this type of the prior art, an axis separated from the mounting axes of a system of parallel links is fixed on a metal piece to support a gear change control cam, a reel connected to cable control means and elastic means. Therefore, the shifting of the prior art is complicated in construction and is comparatively heavy. In addition, the prior art shifting includes an adjusting screw or the like which projects outwardly from a bicycle equipped with such a shifting, and this projecting screw or the like is dangerous because on the other hand, the gear change of the present invention uses the axis 17 of the outer link 16 of the parallel link system to carry the shift control cam 18, the reel 20 connected to the cable control system and a helical spring 19, which allows a simplification of the gear change and a reduction in its weight.

Furthermore, in accordance with the present invention, the elements which are exposed in the gearshifts of the prior art, namely the gearshift control cam 18, the helical spring 19, the adjustment screw 13 and movable member 25 are protected by the cap 7 ′ of the metal part 7 and by the external link 16, so that there are no projections towards the outside of the bicycle. This results in better safety with regard to the bicycle, and the dimensions of the gear change mounted on the bicycle are smaller while providing it with a pleasant appearance.

 It goes without saying that many modifications can be made to the device described and shown without departing from the scope of the invention.

Claims (3)

 1. gear change for a bicycle comprising a pinion with several teeth cooperating with a chain, characterized in that it further comprises a mounting member fixed to the frame of a bicycle; a parallel link system comprising an inner link (9), one end of which is rotatably connected to the mounting member (5) by an axis for mounting the inner link (9) and an outer link (16), one end of which is rotatably connected to the mounting member by a mounting pin of the outer link; a movable member (25) connected to opposite ends of the inner link (9) and the outer link (16); a change plate (33) carrying a guide roller (29) and a tension roller (31) of the chain (4), this change plate (33) being rotatably mounted on the movable member (25); a gear change control cam (18) and a spring (19) urging this cam in a direction of rotation, the cam (they) and the urging spring (19) being carried by the connecting rod mounting axis outer (16), part of the outer link covering the gear change control cam (18), the biasing spring and the outside of the movable member (25); an L-shaped lever (11) pivotally mounted on the mounting axis of the inner link (16) and a lever control spring (10), this lever having one end urged against the gear change control cam (18 ) by this lever control spring (10) while the opposite end can selectively come into contact with the inner link (9), a part of the inner link enclosing the lever in L the lever control spring; a cap (7 ') intended to cover the outer surfaces of the inner link (9) and of the outer link (16), this cap being able to be fixed on the mounting member (5); and a reel (20) fixed on the part of the mounting axis of the outer rod which exceeds the mounting assembly, an inner cable of a cable control system being fixed on this reel (20) which is furthermore arranged to turn with the gear change control cam (18).  2. Gear change according to claim 1-, characterized in that the movable member (25) is able to move in response to a change in the angular position of the gear change control cam (18) by the intermediate of the inner link (9), so as to move the change plate (33) from a position corresponding to one speed to a position corresponding to another speed.  3. Gear change according to claim 2, characterized in that the change plate is able to move the path of the chain (4) as a function of the angular position of the speed change control cam (18), so as to change the development by moving the chain (4) from one toothing on another toothing of the pinion (3).