GB2180601A

GB2180601A - Free wheel devices in transmission mechanism for moped

Info

Publication number: GB2180601A
Application number: GB08522946A
Authority: GB
Inventors: Gin Yung Lim; Sei Tei Wang
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-09-17
Filing date: 1985-09-17
Publication date: 1987-04-01
Also published as: GB8522946D0

Abstract

A transmission mechanism for a moped for transmitting the output motion of an engine to the rear wheel of the moped comprises a chain wheel 22 mounted on the output shaft 21 of the engine and another chain wheel mounted on the crank shaft of the pedals. Freewheels 40 are provided between the output shaft 21 and the chain wheel 22 and between the crank shaft and the other chain wheel. The chain wheel on the crank shaft is then connected to a further chain wheel attached to the rear wheel. Each freewheel 40 includes an intermediate toothed member 42 defining cavities between the rims 41 and 46. Each cavity tapers slightly from one tooth 421 to the next with a helical spring 45 being located in the broader end and a roller 44 in the narrower end. <IMAGE>

Description

SPECIFICATION Improved transmission mechanism for moped This invention relates to a transmission mechanism for a moped which includes improved freewheels for mechanically connecting and disconnecting the crank shaft of the pedals with the other transmitting parts of the mechanism.

Typical transmission mechanisms for transmitting the output motion of an engine or a motor to the crank shaft or the rear wheel usually include a clutch assembly for mechanically connecting and disconnecting the crank shaft of the pedals with the other transmitting parts of the mechanisms.

An object of the invention is to provide a moped with a simple transmission mechanism which does not include any clutch assembly and which includes a novel freewheel.

This and other objects can be achieved in accordance with the present invention through the provision of an improved transmission mechanism for a moped having a frame, a power means mounted on the frame for driving its wheels, and a crank shaft carrying two pedals. The mechanism comprises: a first chain wheel mounted on the power output shaft of the power means; a first freewheel provided between the output shaft and the chain wheel; a second chain wheel mounted on the crank shaft; a second freewheel provided between the crank shaft and the second chain wheel; and a chain connecting the first and second chain wheels; wherein each of the first and second freewheels includes an outer ring member, an intermediate toothed ring member fitted in and fixed to the outer ring member, the toothed ring memer having inwardly projecting teeth spaced apart, an inner ring member inserted in the toothed ring member in a position rotatable relative to the toothed ring member, the teeth, the inner periphery of the intermediate ring member and the outer periphery of the inner ring member defining a plurality of cavities each of which has a narrower portion and a broader portion, rollers provided in the narrower portions and helical springs provided in the broader portions.

The present exemplary preferred embodiment will be described in detail with reference to the following drawings, in which: Figure 1 is an exploded view of a transmission mechanism according to the present invention; and Figure 2 is a cross-sectional view of the transmission mechanism of the same embodiment as that of Fig. 1.

Referring to the drawings, there is shown a transmission mechanism used in a moped for transmitting an output rotational power of a motor or engine to a crank shaft to which two pedals are attached. The mechanism includes a chain wheel 22 mounted on a shaft 21 which is driven by the motor or engine. A freewheel 40 is provided between the shaft 21 and the chain wheel 22.

An additional chain wheel 31, which is connected to the chain wheel 22 by means of a chain 34, is mounted on crank shaft 32. A chain wheel 33, which is adapted to be connected to another chain wheel (not shown) attached to the rear wheel (not shown) of the moped, is mounted on the crank shaft 32 and is fixed to the chain wheel 31. Between the crank shaft 32 and chain wheel 31 is inserted another freewheel 40.

The freewheel 40 includes an outer rim 41 which abuts an the inner periphery of the chain wheel 22 or 31 and has an annular flange 411 projecting inward from one end thereof. An intermediate toothed rim 42 is fixed to the outer rim 41, its outer periphery abutting on the inner periphery of the outer rim 41. The toothed rim 42 is provided with spaced apart teeth 421 which project inwardly. An inner rim 46 is inserted in the toothed rim 42 in a rotatable position relative to the outer rim 41 and intermediate rim 42, the inner periphery of the inner rim 46 sleeved fixedly on the crank shaft 32 or the shaft 21.

The intermediate rim 42 is so constructed that each cavity 43 defined by each two teeth 421, the inner periphery of the rim 42 and the outer periphery of the rim 46 is tapered slightly from one tooth 421 to another adjacent tooth 421 forming a narrower portion 431 and a broader portion 432. Rollers 44 are provided in the cavities 43 respectively and helical springs 45 are provided in the broader portions 432 of the cavities with their ends in contact with the tooth 421 and the roller 44.

In operation, the chain wheel 22 is driven by the engine through the shaft 21 which rotates in the clockwise direction together with the freewheel 40. The freewheel 40 in this situation is in an engaged position since the rollers 44 are moved into the narrower portions of the cavities and engage with the inner surface of the rim 42 and the outer surface of the rim 46. Through the chain 34, the motion of chain wheel 22 is transmitted to chain 31 which is thereby rotated in the clockwise direction together with chain wheel 33. This causes the crank shaft 32 to rotate in the clockwise direction through the freewheel 40 which is engaged in the manner as described above.

If the engine is down off, one can drive the moped by operating the pedals to rotate the shaft 32 in the clockwise direction, without the engine operation. In this situation, the rollers 44 are in the narrower portions of the cavities 43 and therefore the freewheel 40 attached on the shaft 32 is in the engaged position. The motion of the shaft 32 will be transmitted to chain wheels 31 and 33 and then to chain wheel 22 and the rear wheel.

The chain wheel 22 at this condition is mechanically disconnected from the shaft 21 because the freewheel 40 attached thereto is in the disengaged position in which the rollers 44 are moved to the broader portions of the cavities 43 and disengaged from the surfaces of the rims 42 and 46.

The crank shaft 32 can also be rotated by simultaneous operations of the engine and the pedals since the freewheels 40 are in the engaged position in this situation.

With the invention thus explained, it is apparent that various modifications and variations can be made without departing from the scope of the invention. It is therefore intended that the invention be limited as indicated in the appended claims.

Claims

1. A transmission mechanism for a moped having a frame and a power means mounted on the frame for driving its wheels and a crank shaft carrying two pedals comprising: a first chain wheel mounted on the power output shaft of the power means; a first freewheel provided between said output shaft and said chain wheel; a second chain wheel mounted on said crank shaft; a second freewheel provided between said crank shaft and said second chain wheel; and a chain connecting said first and second chain wheels; wherein each of said first and second freewheels includes an outer ring member, an intermediate toothed ring member fitted in and fixed to said outer ring member, said toothed ring member having inwardly projecting teeth spaced apart, an inner ring member inserted in said toothed ring member in a position rotatable relative to said toothed ring member, said teeth, the inner periphery of said intermediate ring member and the outer periphery of the said inner ring member defining a plurality of cavities each of which has a narrower portion and a broader portion, rollers provided in said narrower portions and helical springs provided in said broader portions.

2. A transmission mechanism substantially as described herein with reference to the accompanying drawings.