WO2003064243A1

WO2003064243A1 - Bicycle chain drive

Info

Publication number: WO2003064243A1
Application number: PCT/CZ2003/000005
Authority: WO
Inventors: Karel Hladik
Original assignee: Karel Hladik
Priority date: 2002-01-29
Filing date: 2003-01-28
Publication date: 2003-08-07
Also published as: CZ2002351A3

Abstract

The bicycle chain transmission with a swingarm (42) of the rear wheel, said swingarm being attached off the pedalling centre (3), in said transmission the rear wheel centre (1) of the rear wheel consisting of a hub with internal gear changing. The free strand (22) of the chain (2) is in a certain place, with regard to the swingarm (42) structure, wound up over the setting-up pulley (6) joined to the skeleton (4) of the bicycle. By this any negligible change of tightening of the chain (20) is ensured during the swingarm (42) movement and the chain transmission is not fitted with any usual tightener on a foot (421) of the swingarm (42). Contingent minute change of the strain (2) tightening can be equalized by the setting-up pulley (6) itself which can be joined to the skeleton (4), e.g., by means of a spring-cushioned holder (43). In bicycles with very high position of the hanger (411) of the swingarm, the transmission pattern is completed by an inserted sprocket wheel (5) mounted on the inserted shaft (51) by means of which the traction strand (21) of the chain (2) is led to the proximity of the hanger (411). To the inserted shaft (51) an auxiliary drive unit (8) can be joined. The inserted shaft can be joined by means of threaded cups the pitch of which is 24 threads within British inch.

Description

Bicycle chain drive

Field of Engineering

The invention concerns a drive of a bicycle rear wheel which has a hub with an internal gear changing and can be utilized in industrial production above all.

State ofthe Prior Art

Common feature of modern bicycles with rear wheel swingarm is that the centre ofthe movement curve, traced by rear wheel central axis during movement, is situated out ofthe bicycle pedalling centre. With the swingarm moving, the distance between chain ring and rear cog changes. Then, the chain length must correspond to the greatest distance between these elements and the chain tension must be supported by a chain tightener during swingarm movement. In a typical solution with a derailleur, this problem is solved directly by a derailleur mechanism but in bicycle with an internal gear changing hub, said bicycle having not any said mechanism, the chain tightener must be mounted additionally. For these purposes a chain tightener is known which is based on the structural principle ofthe derailleur mechanism.

Equally as in the derailleur case, this mechanism is attached to a foot ofthe swingarm. This gear is heavy, complicated, easily vulnerable and expensive, too. Besides, it takes away the chain free strand from the traction strand due to which, in effect, it prevents the chain from being housed and approaches the free strand to the ground which is usually the source of contamination for the chain and even for the tightener. The chain tightener pretightens steadily the chain with the result of lower transmission efficiency.

In bicycles with the requirement of optimum running properties at high swingarm stroke (e.g. in special downhill bicycles) the swingarm must be attached so far from the pedalling centre axis that, with the swingarm moving, the change of mutual distance between the rear cog and the chain ring exceeds the possibilities ofthe chain tightener structure. At present, this problem must be solved by means of dividing the drive mechanical transmission ofthe rear wheel drive into two separated transmissions, i.e. by means of a countershaft attached to the bicycle frame as near as possible from the swingarm swing axis or at best in this axis directly (e.g. the bicycle Clifcat, see the journal Mountain Action, January 2001, p. 59). The above mentioned shaft is driven by a chain transmission from the pedalling centre and another chain transmission transmits then the torque from the countershaft to the rear wheel rear cog. The axial spacing of individual elements does not change at all or changes very little. This solution has a new substantial disadvantage. This is due to the presence of another chain transmission with a tightening problem in mounting and servicing work. The maintenance requirements rise and the bicycle weight increases as well. In addition to it, this structure is not being produced worldwide in combination with rear wheel hub with internal gear changing.

Essence ofthe Invention

The above mentioned disadvantages are removed by present solution the essence of which consists in that a setting-up pulley is attached to the bicycle skeleton. The pulley circumference approaches the lower part ofthe chain traction strand. Over this pulley the chain free strand is wound in such a way that the whole chain is divided by the pulley into two loops essentially with one of them wrapping round the rear cog and the second one the chain ring. The places where the free strand reels off the pulley and the traction strand reels on the chain ring, together with analogous points of chain reeling-on and reeling-off on the rear cog, form, at negligible inaccuracy, swivels of a four-joint mechanism on a central element of which the rear cog is located. Starting from this model the swingarm can be designed as a mechanism which ensures in effect exact tracing the theoretical curve ofthe rear cog movement through the rear wheel centre. By this solution, minimum chain tension change is warranted during rear wheel swingarm movement and it is not necessary to make use of operational chain tightener. In practice, it is more advantageous to replace the theoretical curve of rear cog movement by a circular arch and to locate the hanger ofthe one-element swingarm with regard to the centre of this arch. In this case too, acceptable change of chain tightening can be ensured in a certain movement extent and the transmission need not be fitted with any operational tightener. The nearer the setting-up pulley is to the place where the traction strand winds up on the chain ring the more the requested effect is expressive and the more the theoretical rear cog centre curve approaches the circle. Another improvement is rooted in the fact that, with the swingarm clamping being located near the winding-up place ofthe chain traction strand on the chain ring, the chain traction strand tightening does not change and the whole change exists in free strand in effect. This results in accurate and reliable transmission.

Most easily, the required pulley position can be reached by locating the pulley on a suitable, most advantageously movable holder. Therefore, it is advantageous to make a stop for this holder on the bicycle skeleton, said holder being settable advantageously, said holder ensuring suitable pulley position simultaneously with necessary chain tightening and eliminating any possible contact between the tracking and free strands ofthe chain. For mounting and service tightening it is suitable if the holder is attached to the skeleton elastically or if the elastic component forms its part directly. Then, the tightening can come on spontaneously. Such kind of attachment is suitable (e.g. from the point of view ofthe concrete required rear hanger swingarm geometry) even if there is a need for the swingarm hanger to deviate off the area in which the negligible tightening change is guaranteed or if the swingarm strokes are higher. Then the setting-up pulley works as operational tightener. Especially, from the standpoint of transmission noise, the leading pulley made in a form of a chain wheel is advantageous.

By making use ofthe present solution the weight in the area ofthe rear wheel centre and of a bicycle decreases as a whole. The total loss ofthe transmission decreases and its reliability increases from both functional and trouble incidence point of view. This arrangement withdraws the chain from the contamination source and enables to construct easily a housing for the chain or to insert it into the hollow rear swing fork due to the small parallel spacing between both chain strands. Because the pulley need not pretighten the free chain strand in normal position ofthe swingarm, the mechanical transmission loss decreases as well. With respect to that the centre ofthe circle, by which the theoretical curve ofthe rear cog centre motion can be replaced, is located above the pedalling centre, this solution suits especially to design bicycles ofthe high-pivot type. In structures with the swingarm hanger being located extremely high, this can cause a need to complete the transmission pattern by an inserted sprocket wheel situated in the swingarm hanger area where said sprocket wheel is wound round by the chain traction strand. The most suitable place for the setting-up pulley is near the place where chain traction strand is being wound on the inserted sprocket wheel. At all events, the sprocket wheel setup is simpler than the countershaft assembly and the requirement of a single chain transmission is complied. As for the structure, the simplest solution with the inserted sprocket wheel is such where the swingarm, setting-up pulley, and inserted sprocket wheel are mounted on a common component setup containing an inserted shaft. From the standpoint of production costs minimization, it is suitable if equal component setup is used as in the pedalling centre setup characterized by fastening threaded cups according to CSN 014045 with diameter of 34.7 mm and 24 threads within British inch. Slight imperfection ofthe chain line, as it occurs in this case, does not have any substantial influence on operational properties ofthe transmission in the chain free strand above all. However, this structure minimizes insufficiently the operational chain tightening and must be completed by a simple operational tightener.

The sprocket wheel, pulley and swingarm mounting on separate elements directly or by means of holders enables again to better respect geometrical dependencies ofthe transmission and therefore to eliminate the operational tightener. This makes easy the contingent change of individual functional parts ofthe bicycle.

The well-dimensioned inserted shaft and properly modified mounting thereof offers ideal space to connect an auxiliary drive unit contingently. This mounting can be utilized to pivot the head part ofthe bicycle frame if there is any requirement to fold the frame for bicycle transport.

The high-pivot design, occurring in bicycles fitted with a rear wheel swingarm, means that the position ofthe swingarm on the bicycle frame is high above the pedalling centre. In this application, this term is being used for cases where the swingarm holder is on the chain traction strand level or even higher.

The setting-up pulley - this is the pulley the purpose of which is to lead the chain free strand into a certain position necessary to minimize the swingarm movement influence on chain tightening. In addition to the main purpose, it can tighten and lead the chain. It need not be any special product and any existing pulley can be used (e.g., to advantage, a chain pulley of the derailleur tightener as a pulley in the chain wheel form) which serves for other purposes originally.

The inserted sprocket wheel - this is a sprocket wheel inserted into the traction strand in order to change its direction or to connect another gear to existing chain transmission. The operational tightener - this is a tightener necessary for the chain transmission to work and is used to prevent the chain from decreasing and increasing its length in bicycle running due to chain wheel shafts distance changing during swingarm movement.

Survey of Figures on Drawings

On the attached drawings some cases ofthe technical solution embodiment are illustrated where Fig. 1 presents a total view on the bicycle with direct chain leading from the chain ring to the rear cog and Fig. 2 shows the embodiment with inserted sprocket wheel.

Examples on the Embodiment ofthe Invention

On Fig. 1 there is a high-pivot bicycle with direct leading ofthe traction strand 2J_ ofthe chain 2 from the chain ring 3J_ to the rear cog 1_L The free strand 22 ofthe chain 2 is being approached to the traction strand 21 ofthe chain 2 by means ofthe setting-up pulley 6 located near the winding up ofthe traction strand 2J, on the chain ring 3J_, The setting-up pulley 6 is pivoted to the holder 43. The position ofthe holder 43 is limited by the settable stop 431. On the bicycle frame 4_1 the hanger 411 ofthe swingarm 42 is made in the place which is suitable up to certain stroke ofthe swingarm 42 from the point of view of acceptable change ofthe chain 2 tightening. This place is above the pedalling centre 3 and is suitably located from the standpoint ofthe rear swingarm 42 geometry as well as of resulting running properties ofthe bicycle. For case of greater stroke where the chain tightening change cannot be neglected, the holder 43 is joined movably to the frame 4J_ and pressed to the stop 431 by means of a spring 432. This enables the setting-up pulley 6 to move and the necessary tightening ofthe free strand 22 of the chain 2 to be limited.

On Fig. 2, the bicycle is presented the skeleton 2 of which consists of a frame 4J_ with the hanger 411, the swingarm 42, and location ofthe pedalling centre 3. On the frame 4J_ the hanger 411 is placed in a considerable distance from the pedalling centre 3. In this bicycle the rear wheel chain drive is arranged consisting ofthe chain ring 3 _ which is a part ofthe setup ofthe pedalling centre 3, the rear cog J_l, located on the centre ofthe rear wheel centre 1, and ofthe chain 2 with the traction strand 21 and the free strand 22. The traction strand 21 is wound round the inserted sprocket wheel 5 pivoted on the inserted shaft 5_1 in the hollow pin axis ofthe swing hanger 411. The free strand 22 ofthe chain 2 is led by the setting-up pulley 6, attached to the swingarm 42, by means ofthe holder 43 into the position which ensures negligible change ofthe chain 2 tightening during the swingarm 42 movement. The holder 42 position is limited by the stop 431 to which the holder 43 is pressed by means ofthe spring 432. The auxiliary drive unit 8 is connected to the inserted shaft 5J_ by means ofthe belt 7.

Utilizability in the Industry

The rear wheel drive according to the invention can be used especially in production of bicycles for sporting and tourism purposes with low requirements on maintenance, high running reliability, and comfort of using. With sufficiently rigid bicycle skeleton and quality of built-in components, this drive is very suitable even for bicycles determined for extreme sports with highest requirements on bicycle running properties.

rear wheel centre chain pedalling centre skeleton sprocket wheel pulley belt drive unit rear cog traction strand free strand chain ring frame swingarm holder inserted shaft hanger foot stop spring

Claims

Patent Claims

1. A bicycle chain drive consisting of a chain ring hanged on a pedalling centre, of a rear cog mounted on a rear wheel centre consisting of a hub with internal gear changing, and of a chain, said drive being arranged on a bicycle skeleton consisting of a frame with a hanger of a swingarm ofthe rear wheel, said hanger being located essentially off the pedalling centre, and ofthe rear wheel swingarm with a foot, the foot is free ofthe operational chain tightener, characterized in that, to the skeleton (4) a setting-up pulley (6) is joined, by means of said pulley the free strand (22) ofthe chain (2) is positioned in a certain place in neighbourhood of a traction strand (21).

2. A bicycle chain drive according to Claim 1 , characterized in that, the setting-up pulley (6) is joined to the skeleton (4) ofthe bicycle by means of a movable holder (43).

3. A bicycle chain drive according to Claim 2, characterized in that, a stop (431) ofthe holder (430 is made on the skeleton (4) ofthe bicycle.

4. A bicycle chain drive according to Claim 3, characterized in that, the stop (431) ofthe holder (43) is settable.

5. A bicycle chain drive according to Claims 2 to 4, characterized in that, the spring (432) is arranged between the skeleton (4) ofthe bicycle and the holder (43).

6. A bicycle chain drive according to Claims 2 to 4, characterized in that, the holder (43) contains an elastic member.

7. A bicycle chain drive according to Claims 1 to 6, characterized in that, the setting-up pulley (6) is made in a chain wheel form.

8. A bicycle chain drive according to Claims 1 to 7, characterized in that, the traction strand (21) ofthe chain (2) is led over the inserted sprocket wheel (5), joined to the skeleton (4) of the bicycle, in order to change the direction of said traction strand.

9. A bicycle chain drive according to Claim 8, characterized in that, the inserted sprocket wheel (5) is attached to the skeleton (4) ofthe bicycle by means ofthe inserted shaft (51).

10. A bicycle chain drive according to Claim 9, characterized in that, an auxiliary drive unit (8) is connected to the inserted shaft (51).

1. A bicycle chain drive according to Claims 9 and 10, characterized in that, a setup of components for the inserted shaft (51) location is joined to the bicycle skeleton by thereaded cups having a pitch of 24 threads within British inch.