GB1595091A

GB1595091A - Bicycle drive chain

Info

Publication number: GB1595091A
Application number: GB1720878A
Authority: GB
Original assignee: MAEDA IND
Current assignee: MAEDA IND
Priority date: 1977-05-02
Filing date: 1978-05-02
Publication date: 1981-08-05
Also published as: FR2389804B1; FR2389804A1

Description

(54) A BICYCLE DRIVE CHAIN (71) We, MAEDA INDUSTRIES, LTD., of No. 16, 1-Ban, 2cho, Minami Koyo-cho, Sakai, Osaka, Japan, a Japanese company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a bicycle drive chain, designed to cooperate with a bicycle multi-speed free wheel assembly having a plurality of spaced sprocket wheels which are different in diameter and coaxially mounted on a rear wheel hub.

When changing gear on a bicycle equipped with a multi-speed wheel assembly, it is most important to shift the running chain, by means of a derailleur; from one sprocket wheel to another selected one smoothly and quickly without disengagement from the free wheel assembly. Various ways of doing this have been proposed, which provide improvements not in the bicycle chains per se but mostly in bicycle derailleurs and sprocket wheels. For example, it has been proposed to form the teeth of the sprocket wheels rather sharply or to reduce the thickness of each sprocket wheel.

It has also been proposed to minimize the dis tance between adjacent sprocket wheels for easier shifting of the running chain. Many of these attempts have proved to be effective to some extent, but the results have not been entirely satisfactory. Especially in the case where the running chain is switched over from a smaller sprocket wheel to a larger one, the chain occasionally fails to mesh with the teeth of the sprocket wheels, because the chain in this case must climb up the side wall of the larger sprocket wheel.According to the inven tion, there is provided a bicycle drive chain for use with a multi-speed free wheel assembly having a plurality of spaced sprocket wheels which are different in diameter and coaxially mounted on a rear wheel hub spindle in order of diameter from an outermost smallest sprocket wheel to an innermost largest sprocket wheel, said bicycle drive chain comprising: a plurality of inner link plates spaced apart with respect to each other and aligned in two lines extending in parallel with a first predetermined distance therebetween, each of said inner link plates including an outside wall surface; and a plurality of outer link plates disposed on each said outer wall surface of said inner link plates being longitudinally spaced apart with respect to each other and aligned in an inner line and an outer line, extending in parallel with a second predetermined distance therebetween, each of said outer link plates being a single, undeformed piece of flat plate whose outside wall surface is smooth and flat, a lengthwise recess being formed by hollowing out a portion of an inside wall of each of at least the outer link plates disposed in said inner line, each recess being formed partially along a lower marginal edge of each of said outer link plates in said inner line so as to partially slightly enlarge said predetermined distance between an opposed pair of outer link plates extending in said two lines thereby to easily catch an accessible tooth of an adjacent sprocket wheel onto which said chain is selectively shifted, each recess being defined by said lower marginal edge and a curved contour edge extending to surround the recess and having a depth which is deepest at an intermediate portion of said lower marginal edge and is gradually shallower until said contour edge is flush with a non-recessed portion of said inside wall of each outer link plate so that each tooth of said sprocket wheels is smoothly and easily engaged into a space formed between an opposed pair of said outer link plates, a maximum distance between said lower marginal edge and said curved contour edge being predetermined so that each of said outer link plates maintains its extensional rigidity.

The construction of the invention means that the distance between two lines of outer link plates is slightly enlarged for easier engagement of the chain with bicycle sprocket wheels.

The present invention will be further described, by way of example, in conjunction with the accompanying drawings.

In the drawings: Figure 1 is a fragmentary front elevation showing a part of a bicycle drive chain accord ing to the present invention; Figure 2 is a bottom plan view of Figure 1; Figure 3 is a slightly enlarged cross section taken along the lines Ill-Ill of Figure 1; Figures 4 and 5 are similar views to Figure 3, showing modifications of the chain illustrated in Figures 1 to 3; and Figures 6 and 7 are fragmentary prespective views illustrating operation of the chain of the present invention.

Referring now to the drawings, the bicycle drive chain 10 comprises a plurality of inner plates 11, a plurality of outer link plates 12, a plurality of rollers 13, and a plurality of pins 14. The inner link plates 11 and the outer link plates 12 are arranged in pairs of oppo sitely disposed, spaced plates. Each pair of inner link plates 11 is connected at each end to further pairs adjacent thereto by means of a pair of outer plates 12 with pins 14 inserted transversely of the longitudinal axis of the chain 10 through the inner and outer plates 11, 12 which are partly overlapped with each other in the conventional manner. Each of said rollers 13 is interposed between the opposed inner plates 11 so as to be freely rotatable about the axis of each of said pins 14, con ventionally.The rollers 13 are spaced longi tudinally of the chain to form spaces 15a, 15b therebetween, with which each of the teeth of the sprocket wheels are engageable, as shown in Figures 8 and 9.

Each of said outer link plates 12 is partially cut away inwardly from one edge thereof so that a recess 16 is formed in the inside wall of each plate 12. More specifically, the recess 16 is formed at the midportion of the edge of each outer link plate 12 in such a manner that the maximum axial length L1 of the recess 16 is at least larger than the axial length L2 of said space 15a defined between a pair of adjacent rollers 13 as shown in Figure 2. The depth D (Figure 1) of the recess 16 may be as large as possible without detracting from the strength i.e. resistance against tension of the outer link plates, in view of the wall thickness thereof.

The maximum width W (Figure 3) of the recess 16 depends on the wall thickness T of the outer link plate 12. Said recess 16 may have a curved margin 16' as shown in Figure 2 and may gradually reduce in width to present a substantially triangular shape in crosssection as shown in Figure 3. The innermost margin 16" of the recess 16 should be flush with the mside wall surface of the link plate 12. The recess 16 communicates with said space 15a, and as a result, the width of said space 15a is enlarged by 2 X W at its bottom opening end.

Recesses 16 may be formed in the outer link plates 12 on only one side of the chain (Figure 4). The chain will then be put on with the recessed link plates facing the larger sprocket wheels. Further, recesses 16 may be formed in both upper and lower edges of the outer link plates 12a on both sides of the chain, as shown in Figure 5.

In the embodiments shown in Figures 1 to 5, the wall thickness T of the outer link plates 12 may preferably be slightly greater than that of the inner link plates at least to the extent that the sufficient strength required for the outer link plates 12 is maintained even with the recesses 16 formed therein. For instance, the thickness T (Figure 3) of the outer link plate 12 may be about 1.2 mm, while that of the inner link plate 11 may be 0.8mm.

In operation, when the drive chain 10 running in the direction of an arrow E is switched over from a smaller sprocket wheel 17 to a larger sprocket wheel 18 by swinging the running chain in the direction of an arrow Q (Figure 7) by means of a known rear derailleur (not shown) in the conventional manner, the chain 10 must climb up the side wall of the larger sprocket wheel 18, catch the most accessible tooth 1 8a thereof and receive it within the space 1 Sa (Figure 2 and 7) formed between a pair of rollers 13 in order to ride onto and come into engagement with the teeth of the larger sprocket wheel 18.At this moment, the chain of the preesnt invention can catch the most accessible tooth 1 8a ana receive the same within said space 15a more easily than conventional chains because said space 15a is enlarged at its bottom opening by (2 X W).

The next moment, the tooth 18a slides along the inside wall surface of the plate 12 and comes into full engagement with the chain 10.

In this regard, the value of said width W is actually very small since the maximum value of the wall thickness T per se is very small.

However, is should be understood that the shift of the running chain from one sprocket wheel to another is affected by very delicate factors and that even if the actual value of W is so small, it is still very effective to prevent the running chain from mis-engagement with the sprocket wheel teeth during the chain shift operation.

In the case where the running chain 10 is shifted over from the larger sprocket wheel 18 to the smaller sprocket wheel 17, the operation is substantially the same as for the above described case where the chain is shifted over in the reverse director. In fact, it is much easier to shift the chain from a larger sprocket wheel to a smaller one, as compared to the chain shift in the reverse direction, since the chain need not climb up the side wall of the larger sprocket wheel, and, therefore, there is usually no problem in switching over the chain from a larger sprocket wheel onto a smaller one. Thus, substantially the same operation and effect can be expected in the embodiment illustrated in Figure 4 wherein recesses 16 are formed only in the outer link plates 12 on one side of the chain.

Further, in the particular embodiment shown in Figure 5, by forming recesses 16 along both edges of each of the outer link plates 12a, it is possible to make the outer link plate symmetrical with respect to its longitudinal centre line, resulting in convenience and efficiency in the chain assembly process. Further, it is advantageous in that the weight of each outer link plate can be decreased.

In the embodiments illustrated in Figures 1 to 5, provision of said recess 16 naturally causes a reduction in resistance to tension load applied to each of the outer link plates, and as a result the chain could be undesirably stretched. However, this deficiency can be easily overcome by increasing the wall thickness T of the outer link plates.

WHAT WE CLAIM IS:- 1. A bicycle drive chain for use with a multispeed free wheel assembly having a plurality of spaced sprocket wheels which are different in diameter and coaxially mounted on a rear wheel hub spindle in order of diameter from an outermost smallest sprocket wheel to an innermost largest sprocket wheel, said bicycle drive chain comprising: a plurality of inner link plates spaced apart with respect to each other and aligned in two lines extending in parallel with a first predetermined distance therebetween, each of said inner link plates including an outside wall surface; and a plurality of outer link plates disposed on each said outer wall surface of said inner link plates being longitudinally spaced apart with respect to each other and aligned in an inner line and an outer line, extending in parallel with a second predetermined distance theerbetween, each of said outer link plates being a single, undeformed piece of flat plate whose outside wall surface is smooth and flat, a lengthwise recess being formed by hollowing out a portion of an inside wall of each of at least the outer link plates disposed in said inner line, each recess being formed partially along a lower marginal edge of each of said outer link plates in said inner line so as to partially slightly enlarge said predetermined distance between an opposed pair of outer link plates extending in said two lines thereby to easily catch an accessible tooth of an adjacent sprocket wheel onto which said chain is selectively shifted, each recess being defined bar said lower marginal edge and a curved contour edge extending to surround the recess and having a depth which is deepest at an intermediate portion of said lower marginal edge and is gradually shallower until said contour edge is flush with a non-recessed portion of said inside wall of each outer link plate so that each tooth of said sprocket wheels is smoothly and easily engaged into a space formed between an opposed pair of said outer link plates, a maximum distance between said lower marginal edge and said curved contour edge being predetermined so that each of said outer link plates maintains its extensional rigidity.

2. A bicycle drive chain as claimed in claim 1, wherein the wall thickness of each of said outer link plates is greater than that of said inner link plates.

3. A bicycle drive chain as claimed in claim 1 or claim 2, wherein the wall thickness of each of said inner link plates is within a range from about 0.7mm to 0.9mm.

4. A bicycle drive chain as claimed in claim 1, claim 2 or claim 3, wherein the wall thickness of each of said outer link plates is within a range from l.lmm to 1.3mm.

5. A bicycle drive chain substantially as herein described, with reference to Figures 1 to 3 or Figure 4 or Figure 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. illustrated in Figure 4 wherein recesses 16 are formed only in the outer link plates 12 on one side of the chain. Further, in the particular embodiment shown in Figure 5, by forming recesses 16 along both edges of each of the outer link plates 12a, it is possible to make the outer link plate symmetrical with respect to its longitudinal centre line, resulting in convenience and efficiency in the chain assembly process. Further, it is advantageous in that the weight of each outer link plate can be decreased. In the embodiments illustrated in Figures 1 to 5, provision of said recess 16 naturally causes a reduction in resistance to tension load applied to each of the outer link plates, and as a result the chain could be undesirably stretched. However, this deficiency can be easily overcome by increasing the wall thickness T of the outer link plates. WHAT WE CLAIM IS:-

1. A bicycle drive chain for use with a multispeed free wheel assembly having a plurality of spaced sprocket wheels which are different in diameter and coaxially mounted on a rear wheel hub spindle in order of diameter from an outermost smallest sprocket wheel to an innermost largest sprocket wheel, said bicycle drive chain comprising: a plurality of inner link plates spaced apart with respect to each other and aligned in two lines extending in parallel with a first predetermined distance therebetween, each of said inner link plates including an outside wall surface; and a plurality of outer link plates disposed on each said outer wall surface of said inner link plates being longitudinally spaced apart with respect to each other and aligned in an inner line and an outer line, extending in parallel with a second predetermined distance theerbetween, each of said outer link plates being a single, undeformed piece of flat plate whose outside wall surface is smooth and flat, a lengthwise recess being formed by hollowing out a portion of an inside wall of each of at least the outer link plates disposed in said inner line, each recess being formed partially along a lower marginal edge of each of said outer link plates in said inner line so as to partially slightly enlarge said predetermined distance between an opposed pair of outer link plates extending in said two lines thereby to easily catch an accessible tooth of an adjacent sprocket wheel onto which said chain is selectively shifted, each recess being defined bar said lower marginal edge and a curved contour edge extending to surround the recess and having a depth which is deepest at an intermediate portion of said lower marginal edge and is gradually shallower until said contour edge is flush with a non-recessed portion of said inside wall of each outer link plate so that each tooth of said sprocket wheels is smoothly and easily engaged into a space formed between an opposed pair of said outer link plates, a maximum distance between said lower marginal edge and said curved contour edge being predetermined so that each of said outer link plates maintains its extensional rigidity.