WO2005080185A1

WO2005080185A1 - Structure of crank for bicycle

Info

Publication number: WO2005080185A1
Application number: PCT/KR2005/000508
Authority: WO
Inventors: Chi Hoon Jeon
Original assignee: Chi Hoon Jeon
Priority date: 2004-02-25
Filing date: 2005-02-23
Publication date: 2005-09-01
Also published as: KR20050086329A; KR100584525B1

Abstract

In the conventional crank, the wasteful force Fu is generated over the most period except a specified range of angle (about 60 degree). Provided is a crank of which a starting direction and an ending direction are different each other so as to reduce a wasteful force. The crank is characterized in that its shape from the crank axis to the pedal has a curved portion, which is bent roundly in the midst so that a predetermined angle may be formed between its starting direction starting from the crank axis and its ending direction ending toward the pedal.

Description

[DESCRIPTION] [Invention Title) STRUCTURE OF CRANK FOR BICYCLE [Technical Field]

<ι> The present invention relates to a crank of a bicycle and more particularly, relates a structure of a crank of which a starting direction and an ending direction are different each other so as to reduce a wasteful force. [Background Art]

<2> A conventional crank 1, as shown in Fig 1 and 2, is formed to shape a straight bar which connects a pedal 3 to a crank axis 2 and both its starting direction and its ending direction are laid in a straight line.

<3> A pedaling force Fr by a man can be divided into Fe,which is perpendicular to the crank 1 and rotates the crank 1 actually, and Fp,which is horizontal to the crank 1.

<4> Accordingly, a force obtained by subtracting the actual rotating force Fel, Fe3 from the pedaling force Fr becomes a wasteful force Fu.

<5> The amount of the wasteful force Fu is varies according to an angle of the crank 1. A hatched area with oblique lines of a graph shown in Fig 5 stands for the wasteful force Fu.

<6> That is, the wasteful force Fu grows from 0 degree, disappears about 60 degree, increases gradually after 90 degree, and becomes a force to hinder after 270 degree eventually. The reason that the crank keeps rotating despite of the hindering force is because the other pedal is pedaled together.

<7> In the conventional crank, the wasteful force Fu is generated over the most period except a specified range of angle (about δOdegree). Because such a wasteful force Fu is generated severely over the most period including the range from 60 degree to 120 degree, on which transmission effectiveness of pedaling force Fr becomes utter most, there is a structural problem in which a bicycle doesn't work well due to deduction as much as wasted force even thought a user drives a bicycle at his best. <8> In addition, in the conventional crank of a bicycle, there is a problem that requires to compensate strength by using big and heavy material because it is fragile to the centralization of force on a pedal and external impact due to its straight shape, and then a user shall overwork on his knee, ankle, etc so as to give force as much as the wasted force. [Disclosure] [Technical Problem]

<9> The object of the present invention is to provide a crank of a bicycle that reduces wasteful force over a whole period in accordance with its angle and magnifies actual rotating force, thereby to magnify driving force of the bicycle even with a little force. ιo> Another object of the present invention is to provide a crank of a bicycle that has a curved portion in the midst so as to relieve external impact and centralization of a force on a pedal, thereby possibly to make a bicycle by relatively small in volume and light-weighted material. [Technical Solution] n> To perform the above objective, the present invention provide a crank of a bicycle to connect a pedal and a crank axis, In a crank connecting a pedal and a crank axis each other, the crank is characterized in that its shape from the crank axis to the pedal has a curved portion which is bent roundly in the midst so that a predetermined angle may be formed between its starting direction starting from the crank axis and its ending direction ending toward the pedal 12> Further, it is preferable that the angle is about 60 degree at which uttermost force may be presented therein. [Advantageous Effects] 14> According to the present invention, it is possible to reduce wasted force in a whole period, to make the crank rotate at higher speed by magnifying rotating force, and to make a bicycle by relatively small in volume and light-weighted material by forming a curved portion in the midst so that external impact and centralization of force on a pedal is relieved. Thus overload at joints such as knee, ankle, etc is relieved. [Description of Drawings] 15> Fig. 1 is a side view illustrating a structure of a conventional crank of a bicycle; 16> Fig. 2 is a side view illustrating a rotating state of a crank shown in Fig. 1; π> Fig. 3 is a side view illustrating a structure of acrank of a bicycle according to an embodiment of the present invention; i8> Fig. 4 is a side view illustrating a rotating state of a crank shown in Fig. 3; and 19> Fig. 5 is a graph illustrating force to angle of a crank. 20> 1. 10; crank 2; crank axis 2i> 3; pedal A; angle 22> 20; curved portion [Best Mode] 23> The crank is characterized in that its shape from the crank axis to the pedal has a curved portion, which is bent roundly in the midst so that a predetermined angle may be formed between its starting direction starting from the crank axis and its ending direction ending toward the pedal. [Mode for Invention] 24> The crank of a bicycle according to the preferred embodiment of the present, as shown in Fig 3 and 4, the shape of the crank 10,which starts from a crank axis 2 and ends at a pedal 3, includes a curved portion 20 which is being bent roundly in the midst and forms a predetermined angle A between an starting direction starting from the crank axis 2 and an ending direction ending toward the pedal 3 each other. 25> Accordingly, supposing that the crank 10 is a rigid body and the linear distances from the crank axis 2 to the pedal 3 are the same as a conventional crank, pedaling force Fr is divided into Fe-1 perpendicular to the pedal 3 and Fp horizontal to the pedal 3 and those forces are transformed into the crank axis 2 in a short time when the pedaling force Fr is applied on the pedal 3, thereby resulted perpendicular force Fe-2 get to rotate the crank axis 2. 26> For example, because a start angle of a point of application which start at the crank axis 2 operates at which the uttermost power can be presented and which is ahead then the ending direction toward the pedal 3 by the predetermined angle A in the shape of the crank 10 according to the present invention, even though the ending direction ending toward the pedal 3 is as same as that of the conventional crank shown in Fig. 1, thus the perpendicular force Fe-2 as shown in Fig.3 which is applied on the crank axis 2 is magnified efficiently more than the perpendicular force Fe-1 shown in Fig. 1.

<27> In addition, resulted perpendicular force Fe-4, which is applied on the crank axis 2 as shown in Fig.4, is magnified to be quite stronger than the original perpendicular force Fe-3, which is applied on the pedal 3 as shown in Fig 2, when the crank 10 rotates.

<28> Because the direction of the point of application of the crank axis 2 always starts previously than the direction of the powerpoint of the pedal 3 by 60 degree as described above, it is understood that the original perpendicular Fe-1, shown in Fig.l, is magnified into the resultedperpendicular force Fe-2, shown in Fig. 3, and the original perpendicular forceFe-3, shown in Fig.2, is magnified into the resulted perpendicular force Fe-4,shown in Fig.4, too, and further driving force is generated or magnified at top dead point in Fig.3 and bottom dead point in Fig. 4.

<29> Accordingly, as shown in Fig.5, wasteful force Fu gets reduced, that is wasteful force Fu in the hatched area with oblique lines reduced by the area with arrows, and then actual operating force Fe is magnified.

<30> It is preferred that the angle A between the starting direction of the point of operation, which start from the crank axis 2, and the ending direction of the power point, which is given at the pedal 3, is about 60 degree so that uttermost force is able to operate. Such an angle is possible to be optimized in refer to various factors such as mechanism ^"with the other foot, body size of a user, speed, etc.

<3i> Therefore it is possible to reduce wasteful force Fu on the whole period, to make a bicycle that works well even though a user pedals pedal 3 with relatively small in volume force because wasteful force is reduced, and to relieve overload at joints such as knee, ankle, etc.

<32> In addition, even though the crank 10 is supposed as a rigid body, it is possible to relieve or distribute of centralization of the force on the pedal 3 and an external impact so that the crank may be made by relatively small in volume and light-weighted material such as the crank is made of an elastic material . [Industrial Applicability]

<33> It should be noticed that the present invention is not limited to the described embodiment, and changes by the skilled in the art are possible without departing from the idea of the present invention.

<34> For example, even though the curved portion is described round, the curved portion to be made in various forms such as rectangular or having different diameter, etc.

<35> Thus it should be understood that the scope of the present invention is defined not by the detailed description but by the claims and technical idea thereof.

<36>

<37>

Claims

[CLAIMS] [Claim 1] 39> A crank connecting a pedal and a crank axis each other, the crank is characterized in that its shape from the crank axis to the pedal has a curved portion which is bent roundly in the midst so that a predetermined angle may be formed between its starting direction starting from the crank axis and its ending direction ending toward the pedal. [Claim 2] 40> The crank of claim 1, wherein the angle is about 60 degree.