Overrunning clutch

Abstract

An overrunning clutch comprising a ratchet wheel (1) and a plurality of pawls (2) is disclosed. Each of the pawls (2) is rotationally supported on a disk member (5) by a shaft (3). The clutch is characterized by a permanent magnet (4) being fixed on the disk member (5) between the axes of the disk member (5) and the shaft (3) and facing the tail end of each pawl (2). Because each of the pawls are not driven by a spring in the clutch, the clutch could not be malfunction due to the fatigue failure of the spring in the case of frequent heavy load.

Description

[0001] The present invention relates to an overrunning clutch, and more particularly, to a clutch that is in frequently overrunning condition with heavy load.[0002] An inertial centrifugal ratchet is disclosed in Chinese Utility Model patent CN91208227.5, wherein a magnetic ring is provided under the ratchet. The pawls stretch radially outwardly in the direction effected by the centrifugal force when gears are turning so as to mesh with the teeth of the ratchet. According to the technical solution disclosed in the patent, the ratchet can't operate reliably when the pawls do not rotate flexibly, which is due to the centrifugal force that makes the pawls stretch radially outwardly to mesh with the teeth of the ratchet.[0003] A US patent (U.S. Pat. No. 5,205,386) disclosed a pawl and ratchet clutch with a pawl holdback means, wherein a magnet is disposed radially outwardly of associated pawl meshing end. The pawls stretch radially outwardly by the centrifugal force when the driving sha...

AI Technical Summary

Benefits of technology

[0004] The object of the present invention is to provide an overrunning clutch which doesn't need a spring to drive the pawl.

[0012] This invention utilizes the magnetic force to make the pawl and the ratchet engage with each other. Since no springs are applied, there are no problems of fatigue failure. This will significantly extend the service life of the clutch according to this invention in the case of frequently heavy load.

[0013] According to the present invention, the magnet will not contact with the tail end of the pawl during operation. Such formation can ensure that the magnet will not be impinged by the tail end of the pawl during operation, which means that there is no force acting on it directly. Therefore, the magnet will not be worn or be damaged by mechanical force and it will not produce the problems of fatigue failure existing in the prior art because there is no mechanical force acting on the magnet directly. So the service life of the clutch according to this invention can be extended. On the other hand, since the magnet has the nature of shrinking when it is heated and expanding when it is cooled, the clearance between the magnet and the fixed means will be enlarged when the magnet is impinged by the mechanical force and produces heat during operation. In such case the magnet will become loose. According to this invention, there is no direct contact between the magnet and the tail end of the pawl, so the magnet will not become loose when being heated. Such formation can ensure the magnet to operate for a long time and can extend the service life of the clutch of this invention.

[0014] According to this invention, the distance from the tip of the ratchet end of the pawl to the axis of the through hole is larger than that from the tip of the tail end to the axis of the through hole. Such structure can ensure the pawl to move reliably and be influenced by a small magnetic force, therefore it can ensure the reliability of the clutch of this invention.

Problems solved by technology

According to the technical solution disclosed in the patent, the ratchet can't operate reliably when the pawls do not rotate flexibly, which is due to the centrifugal force that makes the pawls stretch radially outwardly to mesh with the teeth of the ratchet.

The spring will be fatigue failure quickly and make the clutch be malfunction.

Such contact and impingement cause damage on magnet or make the magnet become hot.

The clutch could be malfunction when the magnet is damaged.

The magnet will shrink when it is heated and then is relaxed, which will also make the clutch be malfunction.

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