WO1986001781A1

WO1986001781A1 - Tread crank drive mechanism

Info

Publication number: WO1986001781A1
Application number: PCT/EP1985/000490
Authority: WO
Inventors: Harald KÖNIG
Original assignee: Koenig Harald
Priority date: 1984-09-21
Filing date: 1985-09-19
Publication date: 1986-03-27
Also published as: DE8427822U1; EP0194295A1

Abstract

A tread drive mechanism for cycles, including at least a crank arm (14, 16) rotating around a crankshaft (12), and carrying a pedal at its free end (28, 30). The crank arm or arms (14, 16) are separated into two sections (14a, 14b; 16a, 16b) by articulations (20, 22) with axes which run parallel to the crankshaft (12). The sections are spring-loaded, pre-tensioned into a position which forms an angle between the two and can be brought into a straight position against the action of the spring.

Description

CRANKSHAFT ENGINE

The invention relates to a pedal crank engine, in particular for bicycles, with at least one crank arm rotatable about a crankshaft and carrying a pedal at its free end. '

In pedal crank engines of this type, the crank arm generally has the shape of a straight rod of a predetermined length, so that the drive torque to be achieved depends exclusively on the force exerted by the user. An extension of the crank arm would lead to a higher torque with the same force, but is hardly possible because the range of the user's feet is limited when changing between the top and bottom dead center of the pedal.

For the rest, a certain disadvantage of conventional pedal crank engines for bicycles is that cyclists often place one of the pedals as a footrest in the bottom dead center position in which the other pedal is in the other dead center position in which the Exercise is particularly difficult.

The invention has for its object to provide a pedal crank engine of the generic type which enables the exercise of an increased driving force without any significant change in the geometric conditions of the engine.

This object is achieved in a pedal crank engine of the type mentioned in that the crank arm is divided into two sections by a joint with an axis running parallel to the crankshaft and that the sections are resiliently biased into an angled position. A pedal crank engine of this type behaves like a conventional pedal crank engine when moderate driving forces are exerted, since the sections of the crank arms remain in the angled position due to the resilient preload and the crank arms remain like rigid crank arms. Only when a crank arm reaches the area before the bottom dead center and an increased downward force is exerted does this crank arm stretch against the spring action, so that an additional drive torque is exerted. It is particularly advantageous here that the additional force exerted can be brought about solely by loading the lower pedal with the weight of the driver, that is to say without any significant muscle activity. At the same time, the upper pedal is moved out of the area of the top dead center, so that the action of force on the upper pedal is simplified.

The mutual pivoting of the sections of the crank arm is preferably limited to an angular range of 90 to 180 ° by stops. The angling is preferably carried out in such a way that the angled section of the respective upper crank arm is directed forward in the direction of travel.

A preferred exemplary embodiment of the invention is explained in more detail below with reference to the accompanying drawing.

1 to 3 schematically show the pedal crank engine according to the invention in three successive positions;

4 essentially corresponds to the position of FIG. 2, but illustrates the effect of the additional crank arm joint according to the invention.

1 to 4 schematically shows a pedal crank engine - - -

Nes bike shown, the direction of travel is shown by an arrow 10. Crank arms 14, 16 are fastened to a crankshaft 12 in two positions offset by 180 ° with respect to one another. A circle 18 concentrically surrounding the crankshaft illustrates on the one hand the direction of rotation of the crankshaft 12 by the arrow tips superimposed on the circle and on the other hand essentially corresponds to the outline of a chain wheel of a chain drive (not shown overall).

As will be explained below with reference to FIG. 1, the crank arms 14, 16 each comprise an inner section 14a, 16a and an outer section 14b, 16b. The sections are connected to one another by joints 20, 22, the axis of which runs parallel to that of the crankshaft 12. 1, the crank arm sections 14a and 14b or 16a and 16b are at an angle of 90 ° to one another. The pivotability of the sections — of the crank arms 14, 16 with respect to one another is limited, for example, by a stop (not shown) to the range shown from 90 ° to an extended position of the sections or an angle of 180 °. In the right-angled position, the outer sections 14b, 16b are biased by springs 24, 26.

The springs 24, 26 are shown in the drawing for clarity as tension springs arranged freely between the crank arm sections 14a and 14b and 16a and 16b, but in practice they are preferably in the interior of the joints 20, 22 and / or the crank arm. Sections integrated.

The length ratios between the two sections of the crank arms 14, 16 and the permitted pivoting in the joint 20, 22 can be selected differently in practice and can also be adjustable.

At the outer end of the outer sections 14b, 16b of the crank - _ι -

arms 14, 16 are fastened in the usual manner, rotatable pedals 28, 30, the axes of rotation of which are not shown, in turn, are parallel to the axis of the crankshaft 12.

If a force is exerted on the pedals 28, 30 which is below the force of the springs 24, 26, the two crank arms 14, 16 can be regarded as a rigid unit. In this case, they correspond in their function to straight, conventional crank arms, which is illustrated by a dotted line 32 in FIGS. 1 to 3.

The greatest drive torque can be exerted with a force directed essentially from above in accordance with arrow 34 if the front crank arm or the dotted line 32 on the left in the figures of the drawing is essentially in the horizontal position, that is to say approximately two -. see the position "of FIG. 3 and that of FIG. 1. When the pedals 28 and 30 reach the lower or upper dead center position, which is shown in FIG. 2, downward driving forces are corresponding to the arrow 34 If in this case an increased, downward force is exerted on the lower pedal 28 in accordance with the arrow 36, for example by the driver loading the pedal 28 with his body weight, the lower crank arm 14 stretches in opposition to the action of the spring 24. This causes the crank arms to move from the position dotted in Fig. 4 to the position shown in solid lines, which leads to an additional rotation of the crankshaft 12 by an angle denoted by c θ. This rotation generates an additional driving force, and at the same time, the upper pedal 30 comes to a position before top dead center, so that the exertion of force is facilitated.

Claims

EXPECTATIONS

1. Pedal crank engine, in particular for bicycles, with at least one crank arm rotatable about a crankshaft, at its free end carrying a pedal arm, characterized in that the crank arm (14, 16) is articulated by a joint (20, 22) parallel to the crankshaft (12) extending axis is divided into two sections (14a, 14b; 16a, 16b) and that the sections are resiliently biased into an angled position.

2. Pedal crank engine according to claim 1, characterized ge ¬ indicates that the mutual pivoting of the sections (14a, 14b; 16a, 16b) of the crank arm (14,16) in 5 the joint (20,22) by stops at a range of about 90 to about 180 ° is limited.

3. Pedal crank engine according to claim 1, characterized in that the outer section (14b, 0 16b) is angled forwards in relation to the inner section (1a, 16a) of the crank arms (14, 16) in the direction of rotation of the crankshaft.