WO2000051880A1

WO2000051880A1 - Drive system for bicycles

Info

Publication number: WO2000051880A1
Application number: PCT/KR1999/000214
Authority: WO
Inventors: Young-Woo Lee; Doo-Kyung Jung; Sung-Cheon Lee
Original assignee: Lee Young Woo; Jung Doo Kyung; Lee Sung Cheon
Priority date: 1999-03-02
Filing date: 1999-05-03
Publication date: 2000-09-08
Also published as: AU3444599A

Abstract

A drive system for bicycles is disclosed. In the drive system, a crank plate or a cam plate is rotated around two bearings of linearly integrated slide pipes in accordance with a rotating action of a pedal around the drive shaft, thus allowing the integrated slide pipes to slidably move over a crank shaft in opposite directions and to repeatedly and alternately accomplish a fully extended position and a fully retracted position. When the pedal is rotated downwardly at the front section of the drive sprocket during a rotating action of two pedals, the integrated slide pipes fully extend from the crank shaft, thus accomplishing the fully extended position. On the other hand, when the pedal is rotated upwardly at the rear section of the drive sprocket, the integrated slide pipes fully retract over the crank shaft, thus accomplishing the fully retracted position. When a user continuously rotates two pedals while riding a bicycle, each drive system, mounted to each end of the drive shaft, repeatedly and alternately accomplishes the fully extended position and the fully retracted position, thus generating a maximum driving force using a minimum pedaling force.

Description

DRIVE SYSTEM FOR BICYCLES

Technical Field

The present invention relates, in general, to drive systems installed in bicycles in order to rotate the wheels of a bicycle and, more particularly, to a drive system designed to allow the length of crankshafts to be variable in accordance with a rotating action of pedals, thus generating a maximum driving force using a minimum pedaling force of a user while riding a bicycle, the drive system being also designed to be easily and simply used with the drive shaft of a drive sprocket of a conventional bicycle without changing the construction of the bicycle.

Background Art

As well known to those skilled in the art, a known drive system for bicycles comprises a drive sprocket rotatable held on a hub of a bicycle's frame. The drive sprocket is connected to a driven sprocket of a rear wheel through a chain, thus rotating the rear wheel using a pedaling force of a user. That is, two crankshafts are fixedly mounted to the center of the drive sprocket at both sides of the drive sprocket, and radially extend from the center of the drive sprocket to a length in opposite directions and individually have a pedal at the outside end thereof. In such a case, a pedal is rotatably bolted to the outside end of each crankshaft. When a user, sitting on a saddle, pedals the bicycle, the two pedals are rotated with a limited radius of gyration. The pedaling force is transmitted to the driven sprocket of the rear wheel through the chain transmission mechanism, thus rotating the rear wheel and allowing the bicycle to go forward. Such a drive system is a so- called fixed system since the length of each crankshaft is fixed and this limits the radius of gyration of the pedals.

However, such a fixed drive system is problematic in that the radius of gyration of the two pedals is limited due to the fixed length of the crankshafts, and so the pedals merely generate a limited rotating force. Such fixed drive systems thus fail to effectively and optimally drive the bicycles, and force the users to exert their physical energy to pedal the bicycles while riding the bicycles .

In an effort to overcome this problem, a variable drive system for bicycles is proposed as disclosed in Korean Patent Appln. No. 97-58,360. The above Korean variable drive system is designed to be variable in the length of each crankshaft within a limited range in accordance with a rotating position of each pedal. In a detailed description, the above variable drive system comprises two power transmission units 30 and 30' as shown in Fig. 8. The two transmission units 30 and 30' are respectively mounted to both ends of a drive shaft 31 rotatably fitted in the hub 32 of a bicycle's frame. A rotatable lever 33, 33' is mounted to each end of the hub 32 and has a mount shaft 34, 34'. A slide pipe 35, 35' is mounted to the above mount shaft 34, 34' of each rotatable lever 33, 33'. A pedal 36, 36' is attached to the outside end of each . slide pipe 35, 35'. A crank shaft 37, 37' is mounted to a rotating shaft 38, 38' of each power transmission unit 30, 30' and is brought into slidable engagement with a slide hole 39, 39' of each slide pipe 35, 35'. The above rotating shaft 38, 38' of each crank shaft 37, 37' is assembled with an associated power transmission unit 30, 30' so as to be operated in conjunction with the drive shaft 10. In addition, the rotating shaft 38' of the second power transmission unit 30' is also designed to be operated in conjunction with the drive sprocket 40. The above drive sprocket 40 is connected to a driven sprocket (not shown) of a rear wheel through a chain (not shown) .

The above variable drive system is operated as follows. That is, when a pedal 36, 36' is rotated downwardly in the front section of the drive sprocket 40 during a rotating action of the two pedals 36 and 36', the crank shaft 37, 37' associated with the pedal fully extends from the slide pipe 35, 35', thus accomplishing a fully extended position. On the other hand, when the pedal 36, 36' is rotated upwardly in the rear section of the drive sprocket 40, the crank shaft 37, 37' fully retracts into the slide pipe 35, 35', thus accomplishing a fully retracted position. When the user continuously pedals the bicycle, each of the two crank shafts 37 and 37' repeatedly and alternately accomplishes such a fully extended position and such a fully retracted position, thus continuously generating a maximum driving force using a minimum pedaling force of the user.

However, the above variable drive system is problematic in that it is produced as an assembly with one power transmission unit 30, 30', one rotatable lever 33, 33', one slide pipe 35, 35', and one crank shaft 37, 37' being mounted to each end of the hub 32 integrated with a specifically designed drive sprocket 40. Therefore, the variable drive system has so large a volume and so complicated a construction as to reduce both work efficiency and productivity while manufacturing the drive system. This increases the production cost of the drive system for bicycles. Another problem of the above variable drive system resides in that it is designed to be only used with a specifically designed bicycle, thus being not used with an existing bicycle of a user. This reduces compatibility of the drive system and forces a user to purchase a new bicycle, thus being restricted from being more widely used.

Disclosure of the Invention

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a drive system for bicycles, which rotates a crank plate or a cam plate in accordance with a rotating action of a pedal, thus slidably moving linearly integrated slide pipes relative to a crank shaft between a fully extended position and a fully retracted position in a way such that the slide pipes fully extend from the crank shaft and accomplish the fully extended position with the pedal being rotated downwardly at the front section of a drive sprocket, but fully retract over the crank shaft and accomplish the fully retracted position with the pedal being rotated upwardly at the rear section of the drive sprocket, and which thus generates a maximum driving force using a minimum pedaling force of a user in accordance with a leverage of the drive system, and which has a simple construction suitable for simplifying the construction of the drive system for bicycles.

Another object of the present invention is to provide a drive system for bicycles, of which the crank shaft has a rectangular cross-section and is slidably received in the linearly integrated slide pipes, having a rectangular cross-section, in a way such that the crank shaft is only longitudinally slidable in the slide pipes without being rotatable in the slide pipes, and which is easily installed on the drive shaft of a drive sprocket of a conventional bicycle without changing the construction of the bicycle, and which thus has an improved compatibility.

A further object of the present invention is to provide a drive system for bicycles, of which a connection rod, used for connecting the crank shaft to the crank plate or a slide cam case of the cam plate, is divided into two parts that are coupled to each other into a single structure by a length adjustable turnbuckle, thus allowing a user to selectively change the initial length- of the drive system in accordance with his body size. In order to accomplish the above objects, the present invention provides a drive system mounted to each end of a drive shaft of a drive sprocket in bicycles and used for transmitting a rotating force of a pedal to the drive sprocket, comprising: upper and lower slide pipes respectively having a rectangular cross-section and linearly integrated into a single structure using locking means, with two bearings being fixedly set in two bearing seats formed on opposite side walls of the two slide pipes at a junction between the two slide pipes, and an interference-preventing opening being formed from front to back wall of the two slide pipes at the junction of the two slide pipes; a crank shaft axially and movably received into the linearly integrated slide pipes from a free end of the upper slide pipe, thus allowing the integrated slide pipes to be axially movable relative to the crank shaft in opposite directions, the crank shaft normally projecting from the upper slide pipe to an initial length and having a fitting hole at one end thereof, and being fixedly mounted to the drive shaft of the drive sprocket at the fitting hole; a serrated pedal shaft fixedly fitted into a serrated center hole of the pedal, thus being integrated with the pedal, the pedal shaft being coupled to the crank shaft at an inside end thereof, the pedal shaft being rotatable around the drive shaft along with the pedal while generating the rotating force; and a length adjusting and coupling unit used for coupling the pedal shaft to the crank shaft in a way such that the unit transmits the rotating force of the pedal shaft to the drive shaft through both the crank shaft and the integrated slide pipes while automatically changing a position of the integrated slide pipes relative to the crank shaft between a fully extended position and a fully retracted position in accordance with a rotating position of the pedal shaft during a rotating action of the pedal around the drive shaft.

Brief Description of the Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a side view of a bicycle provided with a drive system in accordance with the present invention;

Fig. 2 is an exploded perspective view, showing the construction of a drive system for bicycles in accordance with the primary embodiment of the present invention;

Figs. 3a and 3b are sectional views, showing the operation of the drive system of Fig. 2;

Figs. 4a and 4b are sectional views, showing the operation of a drive system for bicycles in accordance with the second embodiment of this invention;

Fig. 5 is an exploded perspective view, showing the construction of a drive system for bicycles in accordance with the third embodiment of this invention;

Figs. 6a and 6b are sectional views, showing the operation of the drive system of Fig. 5;

Figs. 7a and 7b are sectional views, showing the operation of a drive system for bicycles in accordance with the fourth embodiment of this invention; and

Fig. 8 is an exploded perspective view, showing the construction of a variable drive system for bicycles in accordance with the prior art.

Best Mode for Carrying Out the Invention

Fig. 1 is a side view of a bicycle provided with a drive system in accordance with the present invention. Fig. 2 is an exploded perspective view, showing the construction of a drive system for bicycles in accordance with the primary embodiment of the present invention. Figs. 3a and 3b are sectional views, showing the operation of the drive system of Fig. 2.

As shown in the drawings, the drive system 1 of this invention is mounted to each end of the drive shaft 52 of a drive sprocket 51. The drive system 1 comprises upper and lower slide pipes 2 and 2', which have a rectangular cross-section and are linearly assembled into a single structure using a locking means or a plurality of set screws 3. The above screws 3 longitudinally pass through the lower pipe 2' at corners prior to being longitudinally threaded into the upper pipe 2. The two slide pipes 2 and 2 ' individually have two semicircular bearing seats 4, 4' on opposite side walls thereof at the junction between them. The two pipes 2 and 2' are linearly assembled to each other, with two bearings 5 and 5' being respectively set in two circular bearing seats defined at the junction by the semicircular bearing seats 4 and 4' of the two slide pipes 2 and 2'. In addition, an opening 6, 6' is formed from the front to the back wall at the junction of the two slide pipes 2 and 2' and is used for preventing any interference of a yoke, comprising two parallel crank plates 9 and 9', with the slide pipes 2 and 2' during a rotating action of the yoke inside the pipes 2 and 2' as will be described later herein.

A crank shaft 7 is axially and movably received into the linearly assembled slide pipes 2 and 2' from the free end of the upper slide pipe 2, thus being longitudinally slidable in the pipes 2 and 2'. A first end of the crank shaft 7 has a fitting hole 8 through which the crank shaft 7 is fixedly coupled to one end of the drive shaft 52 of the drive sprocket 51.

In such a case, it is necessary for the fitting hole 8 to have a polygonal configuration, such as a rectangular configuration, so as to prevent the drive shaft 52 from rotating idle in the hole 8.

In order to automatically change the movable position of the integrated slide pipes 2 and 2' between a fully extended position and a fully retracted position over the crank shaft 7 in accordance with a rotating position of an associated pedal 16 during a pedaling action of two pedals 16, the drive system 1 has a length adjusting and coupling unit. In the primary embodiment, the length adjusting and coupling unit comprises two parallel crank plates 9 and 9' which are connected to a second end of the crank shaft 7 through a connection rod 13. The two crank plates 9 and 9' are integrated into a yoke at first end portions thereof by a hinge shaft 10. A rotating shaft 11 is externally formed on a second end portion of the first crank plate 9, while a pedal shaft hole 12 is formed on a second end portion of the second crank plate 9'. In addition, the connection rod 13 is divided into two parts that are coupled to each other using a turnbuckle 14. A first end of the connection rod 13 is hinged to the second end of the crank shaft 7, while a second end of the connection rod 13 is hinged to the hinge shaft 10 of the yoke. The rotating shaft 11 of the first crank plate 9 is rotatably fitted into the first bearing 5 which is fixedly seated in the first bearing seat 4 formed at the junction of the two slide pipes 2 and 2'. On the other hand, the pedal shaft hole 12 of the second plate 9' receives the inside end of a serrated pedal shaft 15 with the second bearing 5' being fitted over the pedal shaft 15 in the second bearing seat 4' of the two slide pipes 2 and 2'. Therefore, the yoke, comprising the two crank plates 9 and 9', is rotatable around the two bearings 5 and 5' in accordance with a rotating action of the pedal shaft 15 around the drive shaft 52 of the drive sprocket 51. This will be described in detail later herein.

In the present invention, it is necessary to design the pedal shaft 15 to be prevented from rotating idle in the pedal shaft hole 12 of the second crank plate 9'. In order to accomplish the above object, the pedal shaft 15 may be welded to the pedal shaft hole 12. Alternatively, both the inside end of the shaft 15 and the hole 12 may be designed to have a polygonal cross-section suitable for preventing any idle rotating action of the pedal shaft 15 in the shaft hole 12. In addition, it is preferable to form a scale 20 along one longitudinal surface of the crank shaft 7, thus allowing a user to adjust the initial length of the crank shaft 7 normally projecting from the slide pipes 2 and 2' in accordance with his body size. A pedal 16 is fitted over the pedal shaft 15. In such a case, the center hole 17 of the pedal 16 is serrated in order to meet the serrations of the pedal shaft 15, thus preventing the pedal 16 from rotating idle around the pedal shaft 15. The outside end of the pedal shaft 15 is tightened by a bolt 19 with a washer 18.

Figs. 4a and 4b are sectional views, showing a drive system for bicycles in accordance with the second embodiment of this invention. In the second embodiment, the general shape of the drive system 1 remains the same as that described for the primary embodiment, but the length adjusting and coupling unit is altered as follows. In the following description, the elements common to both the primary and second embodiments will carry the same reference numerals as that of the primary embodiment. In the drive system 1 of the second embodiment, upper and lower slide pipes 2 and 2 ' , individually having a rectangular cross-section, are linearly assembled into a single structure using a plurality of set screws 3 in the same manner as that described for the primary embodiment. The two slide pipes 2 and 2' individually have two semicircular bearing seats 4, 4' on opposite side walls at the junction between them. Therefore, when the two pipes 2 and 2 ' are linearly integrated into a single body, two bearings 5 and 5' are respectively set in two circular bearing seats defined at the junction by the semicircular bearing seats 4 and ' of the two slide pipes 2 and 2 ' .

A crank shaft 7 is axially and movably received into the linearly assembled slide pipes 2 and 2' from the free end of the upper slide pipe 2, thus being slidable in the pipes 2 and 2' in a longitudinal direction. A first end of the crank shaft 7 has a fitting hole 8 through which the crank shaft 7 is fixedly mounted to one end of the drive shaft 52 of the drive sprocket 51. In the second embodiment, the inside end of the serrated pedal shaft 15 extends longer than that of the primary embodiment and fully passes through the two bearings 5 and 5'. Of course, a pedal 16 is fitted over the pedal shaft 15, with the center hole 17 of the pedal 16 being serrated in order to meet the serrations of the pedal shaft 15 and preventing the pedal 16 from rotating idle around the pedal shaft 15. The outside end of the pedal shaft 15 is tightened by a bolt 19 with a washer 18. Different from the primary embodiment, the length adjusting and coupling unit comprises a single crank plate 9 in place of the two crank plates 9 and 9' of the primary embodiment. One end portion of the single crank plate 9 is fixed to the inside end of the pedal shaft 15 at a position outside the first bearing 5 of the two slide pipes 2 and 2'. In such a case, the integration of the pedal shaft 15 with the crank plate 9 is preferably accomplished through a welding process. The above crank plate 9 is also coupled to the first end portion of the crank shaft 7 using a connection rod 13 parallely and externally extending along the integrated slide pipes 2 and 2 ' . In the same manner as that described for the primary embodiment, the above connection rod 13 is divided into two parts that are coupled to each other using a turnbuckle 14. Both ends of the connection rod 13 are hinged to the first end portion of the crank shaft 7 and the other end portion of the crank plate 9, respectively. Therefore, the crank plate 9 is rotatable around the two bearings 5 and 5' in accordance with a rotating action of the pedal shaft 15 around the drive shaft 52. This will be described in detail later herein.

In addition, it is preferable to form a scale 20 along one longitudinal surface of the crank shaft 7, thus allowing a user to adjust the initial length of the crank shaft 7 normally projecting from the integrated slide pipes 2 and 2' in accordance with his body size.

Figs. 5, 6a and 6b are views, showing a drive system for bicycles in accordance with the third embodiment of this invention. In the third embodiment, the general shape of the drive system 1 remains the same as that described for the primary embodiment, but the two parallel crank plates 9 and 9' of the length adjusting and coupling unit are substituted with a circular cam plate 10a, which internally and rotatably engages with an annular slide cam case 12a and is positioned inside the integrated slide pipes 2 and 2 ' . In the following description, those elements common to both the primary and third embodiments will carry the same reference- numerals as that of the primary embodiment and further explanation is not deemed necessary.

In the third embodiment, the second end of the crank shaft 7, longitudinally and slidably received in the integrated slide pipes 2 and 2 ' , is connected to the slide cam case 12a, rotatably fitted over the cam plate 10a, through a connection rod 13. The above connection rod 13 comprises two parts which are coupled to each other into a single body through a turnbuckle 14 in the same manner as that described for the primary embodiment. The above cam plate 10a has a pedal shaft hole 11a at an eccentric position. The inside end of the serrated pedal shaft 15 extends longer than that of the primary embodiment and fully passes through the two bearings 5 and 5' of the two slide pipes 2 and 2' while passing through the pedal shaft hole 11a of the cam plate 10a at a position between the two bearings 5 and 5'. In this embodiment, the inside end of the pedal shaft 15 is fixed to the pedal shaft hole 11a, thus being prevented from rotating idle in the pedal shaft hole 11a. In order to accomplish the above object, the pedal shaft 15 may be welded to the pedal shaft hole 11a. Alternatively, both the end of the shaft 15 and the hole 11a may be designed to have a polygonal cross-section suitable for preventing any idle rotating action of the pedal shaft 15 in the shaft hole 11a. In the third embodiment, the above cam plate 10a is eccentrically rotatable around the two bearings 5 and 5' in accordance with a rotating action of the pedal shaft 15 around the drive shaft 52. This will be described in detail later herein.

Figs. 7a and 7b are sectional views, showing a drive system for bicycles in accordance with the fourth embodiment of this invention. In the fourth embodiment, the general shape of the drive system 1 remains the same as that described for the second embodiment, but the single crank plate 9 of the length adjusting and coupling unit is substituted with a circular cam plate 10a, which internally and rotatably engages with an annular slide cam case 12a and is positioned outside the integrated slide pipes ^"2 and 2'. In the following description, the elements common to both the second and fourth embodiments will carry the same reference numerals as that of the second embodiment and further explanation is not deemed necessary.

In the fourth embodiment, the inside end of the serrated pedal shaft 15 fully passes through the two bearings 5 and 5' of the integrated slide pipes 2 and 2'. One the other hand, the first end portion of the crank shaft 7, axially and slidably received into the integrated slide pipes 2 and 2', is connected to the slide cam case 12a, which is rotatably fitted over the cam plate 10a and is positioned outside the two slide pipes 2 and 2', through a connection rod 13 externally and parallely extending along the slide pipes 2 and 2 ' . The above connection rod 13 comprises two parts coupled to each other through a turnbuckle 14. The above cam plate 10a has a pedal shaft hole 11a at an eccentric position. The inside end of the serrated pedal shaft 15, fully passing through the two bearings 5 and 5 ' of the integrated slide pipes 2 and 2', is fixed to the pedal shaft hole 11a of the cam plate 10a at a position outside the bearing 5. In this embodiment, it is necessary to fixedly mount the inside end of the pedal shaft 15 to the pedal shaft hole 11a of the cam plate 10a so as to prevent the pedal shaft 15 from rotating idle in the pedal shaft hole 11a. In order to accomplish the above object, the pedal shaft 15 may be welded to the pedal shaft hole 11a. Alternatively, both the inside end of shaft 15 and the hole 11a may be designed to have a polygonal cross- section suitable for preventing any idle rotating action of the pedal shaft 15 in the shaft hole 11a. In the fourth embodiment, the above cam plate 10a is eccentrically rotatable around the two bearings 5 and 5' in accordance with a rotating action of the pedal shaft 15 around the drive shaft 52. This will be described in detail later herein. In the drawings, the reference numeral 50 denotes a frame of a bicycle having a drive system 1 of this invention.

The operational effect of a drive system 1 of this invention will be described hereinbelow. In the case of the drive system 1 according to the primary embodiment, two drive systems 1 are fixedly mounted to both ends of the drive shaft 52 of the drive sprocket 51 while radially extending from the shaft 52 in opposite directions. In such a case, each drive shaft 52 is fixedly fitted into the fitting hole 8 of the crank shaft 7 of each system 1, thus being prevented from rotating idle relative to the fitting hole 8. When a user, riding on the saddle of the bicycle, rotates the two pedals 16 forwardly so as to allow the bicycle to go forward, the linearly integrated slide pipes 2 and 2' of a downwardly rotated drive system 1 at the front section of the drive sprocket 51 fully extend from the crank shaft 7, thus reaching a fully extended position. In such a case, the slide pipes 2 and 2' of an upwardly rotated drive system 1 at the rear section of the drive sprocket 51 fully retracts over the crank shaft 7, thus reaching a fully retracted position. Therefore, the two drive systems 1 generate a maximum driving force using a minimum pedaling force of a user while riding a bicycle. That is, when the user pedals the bicycle, one pedal, or a first pedal 16, is rotated downwardly at the front section of the drive sprocket 51 as shown in Fig. 3a, thus rotating the pedal shaft 15 around the drive shaft 52 in the same direction. Therefore, the yoke, comprising two parallel crank plates 9 and 9', is rotated around the center of the bearings 5 and 5' in the same direction.

When the yoke, comprising the two crank plates 9 and 9', is rotated as described above, the linearly integrated slide pipes 2 and 2' fully extend from the crank shaft 7 so as to reach the fully extended position. In such a fully extended position, the drive system 1 generates the maximum driving force using the minimum pedaling force of the user. In such a case, the connection rod 13, hinged to both the hinge shaft 10 of the two crank plates 9 and 9' and the second end of the crank shaft 7 at both ends thereof, effectively transmits the rotating force of the pedal 16 to the crank shaft 7 while converting the rotating action of the pedal 16 around the drive shaft 52 into a linear moving action of the crank shaft 7 in the integrated slide pipes 2 and 2'.

When it is necessary for a user to adjust the initial length of the drive system 1 in accordance with his body size, the initial length of the crank shaft 7 normally projecting from the integrated slide pipes 2 and 2' is easily controlled by rotating the turnbuckle 14 of the connection rod 13 in either direction prior to assembling the parts of the two drive systems 1 with the drive shaft 52. In such a case, the user has to precisely adjust the initial length of each drive system 1, provided at each side of the drive sprocket 51, while carefully observing the scale 20 of the crank shaft 7 so as to allow the two drive systems 1 to have the same initial length.

During such a pedaling action of the user, the other pedal, or a second pedal 16, is rotated upwardly at the rear section of the drive sprocket 51. In such a case, the pedal shaft 15 of the second pedal 16 is rotated around the drive shaft 52 in the same direction as shown in Fig. 3b. Therefore, the yoke, comprising the two parallel crank plates 9 and 9', is rotated around the center of the bearings 5 and 5' in the same direction.

When the yoke, comprising the two crank plates 9 and 9', is rotated as described above, the linearly integrated slide pipes 2 and 2' fully retract over the crank shaft 7 so as to reach the fully retracted position. Such a fully retracted position of the slide pipes 2 and 2' is to be changed into the fully extended position during a next pedaling action of the user.

In the above operation of the two drive systems 1 according to the primary embodiment during a pedaling action, the yoke, comprising the two crank plates 9 and 9', of each drive system 1 is stably rotated in the linearly integrated slide pipes 2 and 2'. However, when the yoke is undesirably and eccentrically rotated in the slide pipes 2 and 2', the yoke is exposed from the slide pipes 2 and 2' through the openings 6 and 6' while being rotated, thus being prevented from an interference with any slide pipe 2, 2'.

On the other hand, the drive system 1 of the second embodiment is operated in the same manner as that described for the primary embodiment. That is, when a user pedals the bicycle, one pedal, or the first pedal 16, is rotated downward at the front section of the drive sprocket 51 as shown in Fig. 4a, thus rotating the pedal shaft 15 around the drive shaft 52 in the same direction. The single crank plate 9 is thus rotated around the center of the bearings 5 and 5' in the same direction. In such a case, the linearly integrated slide pipes 2 and 2 ' fully extend from the crank shaft 7 so as to reach a fully extended position and allow the drive system 1 to generate a maximum driving force using a minimum pedaling force of the user. During the above pedaling action, the other pedal, or the second pedal 16, is rotated upwardly at the rear section of the drive sprocket 51. In such a case, the pedal shaft 15 of the second pedal 16 is rotated around the drive shaft 52 in the same direction as shown in Fig. 4b. Therefore, the single crank plate 9 is rotated around the center of the bearings 5 and 5' in the same direction. This allows the linearly integrated slide pipes 2 and 2' to fully retract over the crank shaft 7 and to reach the fully retracted position. Such a fully retracted position of the slide pipes 2 and 2' is to be changed into the fully extended position during a next pedaling action of the user. When the user continuously pedals the bicycle, each of the two drive systems 1, provided at both sides of the drive sprocket 51, repeatedly and alternately accomplishes the fully extended position and the fully retracted position, thus generating the maximum driving force using the minimum pedaling force of the user.

The drive system 1 of the third embodiment is operated as follows. When a user, riding on the saddle of the bicycle, rotates the two pedals 16 forwardly so as to allow the bicycle to go forward, one pedal, or the first pedal 16, is rotated downward at the front section of the drive sprocket 51 as shown in Fig. 6a, thus rotating the pedal shaft 15 around the drive shaft 52 in the same direction. Therefore, the cam plate 10a, fixed to the pedal shaft 15 at the pedal shaft hole 11a and slidably received in the slide cam case 12a, is eccentrically rotated around the bearings 5 and 5' in the same direction. When the cam plate 10a is eccentrically rotated in the slide cam case 12a as described above, the linearly integrated slide pipes 2 and 2' fully extend from the crank shaft 7 so as to reach a fully extended position. In such a fully extended position, the drive system 1 generates a maximum driving force using a minimum pedaling force of the user.

In such a case, the connection rod 13, hinged to both the slide cam case 12a and the second end of the crank shaft 7 at both ends thereof, effectively transmits the rotating force of the pedal 16 to the crank shaft 7 while converting the rotating action of the pedal 16 around the drive shaft 52 into a linear moving action of the crank shaft 7 in the slide pipes 2 and 2'.

When it is necessary for a user to adjust the initial length of the drive system 1 in accordance with his body size, the initial length of the crank shaft 7 normally projecting from the integrated slide pipes 2 and 2' is easily controlled by rotating the turnbuckle 14 of the connection rod 13 in either direction prior to assembling the parts of the two drive systems 1 with the drive shaft 52. In such a case, the user has to precisely adjust the initial length of each drive system 1 while observing the scale 20 of the crank shaft 7 so as to allow the two drive systems 1 to have the same initial length.

During such a pedaling action of the user, the other pedal, or the second pedal 16, is rotated upwardly at the rear section of the drive sprocket 51. In such a case, the pedal shaft 15 of the second pedal 16 is rotated around the drive shaft 52 in the same direction as shown in Fig. 6b. Therefore, the cam plate 10a, fixed to the pedal shaft 15 at the pedal shaft hole 11a and slidably fitted in the slide cam case 12a, is eccentrically rotated around the bearings 5 and 5' in the same direction.

When the cam plate 10a is eccentrically rotated in the slide cam case 12a as described above, the linearly integrated slide pipes 2 and 2' fully retract over the crank shaft 7 so as to reach a fully retracted position. Such a fully retracted position of the slide pipes 2 and 2' is to be changed into the fully extended position during a next pedaling action of the user.

In the above operation of the two drive systems 1 during a pedaling action, the cam plate 10a of each drive system 1 is stably rotated in the linearly integrated slide pipes 2 and 2'. However, when the cam plate 10a is undesirably eccentrically rotated in the slide pipes 2 and 2', the cam plate 10a is exposed from the slide pipes 2 and 2' through the openings 6 and 6', thus being prevented from an interference with any slide pipe 2, 2'. On the other hand, the drive system 1 of the fourth embodiment is operated in the same manner as that described for the third embodiment. That is, when a user pedals the bicycle, one pedal, or the first pedal 16, is rotated downward at the front section of the drive sprocket 51 as shown in Fig. 7a, thus rotating the pedal shaft 15 around the drive shaft 52 in the same direction. Therefore, the cam plate 10a, fixed to the pedal shaft 15 at the pedal shaft hole 11a, is eccentrically rotated in the slide cam case 12a around the bearings 5 and 5' in the same direction. When the cam plate 10a is eccentrically rotated in the slide cam case 12a as described above, the linearly integrated slide pipes 2 and 2 ' f lly extend from the crank shaft 7 so as to reach a fully extended position. In such a fully extended position, the drive system 1 generates a maximum driving force using a minimum pedaling force of the user.

During the above pedaling action, the other pedal, or the second pedal 16, is rotated upwardly at the rear section of the drive sprocket 51. In such a case, the pedal shaft 15 of the second pedal 16 is rotated around the drive shaft 52 in the same direction as shown in Fig. 7b. Therefore, the cam plate 10a, fixed to the pedal shaft 15 at the pedal shaft hole 11a, is eccentrically rotated in the slide cam case 12a around the bearings 5 and 5' in the same direction. When the cam plate 10a is eccentrically rotated in the slide cam case 12a as described above, the linearly integrated slide pipes 2 and 2' fully retract over the crank shaft 7 so as to reach a fully retracted position. Such a fully retracted position of the slide pipes 2 and 2' is to be changed into the fully extended position during a next pedaling action of the user. When the user continuously rotates the pedals while riding the bicycle, each of the two drive systems 1, provided at both sides of the drive sprocket 51, repeatedly and alternately accomplishes the fully extended position and the fully retracted position, thus generating the maximum driving force using the minimum pedaling force of the user in accordance with a leverage.

Industrial Applicability

As described above, the present invention provides a drive system for bicycles. In the drive system of this invention, a crank plate or a cam plate is rotated around bearings in accordance with a rotating action of a pedal around the drive shaft of a drive sprocket, thus allowing linearly integrated slide pipes to slidably move over a crank shaft in opposite directions and to repeatedly and alternately accomplish a fully extended position and a fully retracted position. Two drive systems, mounted to both ends of the drive shaft, thus generate a maximum driving force using a minimum pedaling force of a user. That is, when a pedal is rotated downwardly at the front section of the drive sprocket during a rotating action of the two pedals, the linearly integrated slide pipes associated with the downwardly rotated pedal fully extend from the crank shaft, thus accomplishing the fully extended position. On the other hand, when the pedal is rotated upwardly at the rear section of the drive sprocket, the linearly integrated slide pipes fully retract over the crank shaft, thus accomplishing the fully retracted position. When the user continuously rotates the two pedals while riding a bicycle, each of the two drive systems repeatedly and alternately accomplishes the fully extended position and the fully retracted position, thus generating the maximum driving force using the minimum pedaling force of the user in accordance with a leverage.

The drive system of this invention has a simple construction suitable for simplifying the construction of a drive system for bicycles. In the drive system of this invention, the crank shaft, having a rectangular cross- section, is axially and slidably received in the linearly integrated slide pipes, having a rectangular cross- section, in a way such that the crank shaft is only axially slidable in the integrated slide pipes without being rotatable in said slide pipes.

Another advantage of the above drive system resides in that it is easily installed on the drive shaft of a conventional bicycle without changing the construction of the bicycle. The drive system of this invention thus has an improved compatibility. On the other hand, the connection rod, used for connecting the crank shaft to either the crank plate or the slide cam case of the cam plate, is divided into two parts. The two parts of the connection rod are coupled to each other into a single body by a length adjustable turnbuckle. Therefore, the initial length of the drive system is adjustable by a user in accordance with a body size of the user.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

Claims :

1. A drive system mounted to each end of a drive shaft of a drive sprocket in bicycles and used for transmitting a rotating force of a pedal to the drive sprocket, comprising: upper and lower slide pipes respectively having a rectangular cross-section and linearly integrated into a single structure using locking means, with two bearings being fixedly set in two bearing seats formed on opposite side walls of said two slide pipes at a junction between the two slide pipes, and an interference-preventing opening being formed from a front to back wall of the two slide pipes at the junction of the two slide pipes; a crank shaft axially and movably received into the linearly integrated slide pipes from a free end of the upper slide pipe, thus allowing the integrated slide pipes to be axially movable relative to the crank shaft in opposite directions, said crank shaft normally projecting from the upper slide pipe to an initial length and having a fitting hole at one end thereof, and being fixedly mounted to the drive shaft of the drive sprocket at said fitting hole; a serrated pedal shaft fixedly fitted into a serrated center hole of said pedal, thus being integrated with the pedal, said pedal shaft being coupled to the crank shaft at an inside end thereof, said pedal shaft being rotatable around the drive shaft along with the pedal while generating the rotating force; and a length adjusting and coupling unit used for coupling the pedal shaft to the crank shaft in a way such that the unit transmits the rotating force of the pedal shaft to the drive shaft through both the crank shaft and the integrated slide pipes while automatically changing a position of the integrated slide pipes relative to the crank shaft between a fully extended position and a fully retracted position in accordance with a rotating position of the pedal shaft during a rotating action of the pedal around the drive shaft.

2. The drive system according to claim 1, wherein a scale is provided along one longitudinal surface of said crank shaft, thus allowing a user to adjust the initial length of the crank shaft.

3. The drive system according to claim 1, wherein said length adjusting and coupling unit comprises: a crank plate rotatably connected to the crank shaft at a first end portion thereof and rotatably held by the two bearings of the integrated slide pipes at a second end portion thereof, with the serrated pedal shaft fixedly engaging with the second end portion of the crank plate, thus allowing the crank plate to be eccentrically rotatable around the two bearings in accordance with the rotating action of the pedal while moving the integrated slide pipes relative to the crank shaft between the fully extended position and the fully retracted position; and a connection rod connecting the crank shaft to the first end portion of the crank plate, thus transmitting an eccentric rotating force of the crank plate to said crank shaft while converting a rotating action of the crank plate into a linear moving action of the crank shaft in the integrated slide pipes.

4. The drive system according to claim 3, wherein said crank plate, rotatably held by the two bearings, is positioned inside the integrated slide pipes, with said connection ^"rod connecting the crank shaft to the crank plate while axially extending inside the integrated slide pipes.

5. The drive system according to claim 3, wherein said crank plate, rotatably held by the two bearings, is positioned outside the integrated slide pipes, with said connection rod connecting the crank shaft to the crank plate while externally extending along the integrated slide pipes.

6. The drive system according to claim 1, wherein said length adjusting and coupling unit comprises: an annular slide cam case connected to the crank shaft at one end thereof; a circular crank cam internally and rotatably engaging with said slide cam case, said crank cam fixedly engaging with the pedal shaft at an eccentric position thereof with the pedal shaft being rotatably held by the two bearings of the integrated slide pipes, said crank cam thus being eccentrically rotatable around the two bearings in accordance with the rotating action of the pedal while moving the integrated slide pipes relative to the crank shaft between the fully extended position and the fully retracted position; and a connection rod connecting the slide cam case to the crank shaft, thus transmitting an eccentric rotating force of the crank cam to said crank shaft while converting a rotating action of the crank cam into a linear moving action of the crank shaft in the integrated slide pipes.

7. The drive system according to claim 6, wherein both the slide cam case and the crank cam, held by the two bearings, are positioned inside the integrated slide pipes, with said connection rod connecting the crank shaft to the crank cam while axially extending inside the integrated slide pipes.

8. The drive system according to claim 6, wherein both the slide cam case and the crank cam, held by the two bearings, are positioned outside the integrated slide pipes, with said connection rod connecting the crank shaft to the crank cam while externally extending along the integrated slide pipes.

9. The drive system according to claim 3 or 6, wherein said connection rod comprises two separate longitudinal parts linearly coupled to each other using a turnbuckle, thus being adjustable in length.