Machine element or mechanism – Elements – Cranks and wrist pins
Patent
1986-11-05
1989-01-03
Smith, Gary L.
Machine element or mechanism
Elements
Cranks and wrist pins
1525016, B60S 124
Patent
active
047948183
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a transmission mechanism, for windscreen wipers in particular, between a rotary drive shaft fixed in relation to a support and a crank arm or similar for actuating an alternating oscillating motion, it being possible to reverse the direction of rotation of the rotary shaft.
The transmission mechanisms aimed at by the invention are of the kind comprising a crank of a variable effective length, this length having a first value under normal operation for a given direction of rotation of the shaft, whilst an increase of the effective length of the crank is actuated when operation is stopped by a reversal of the direction of rotation of the shaft. In the case where such a mechanism is used for the actuation of windscreen wipers, these latter assume a withdrawn position or "parked position" when, after normal operation has been stopped, the increase of the normal length of the crank is actuated.
Such mechanisms comprise: an eccentric, secured for rotation on the drive shaft, the said eccentric being mounted in a bore provided in the crank; means for locking the rotation between the eccentric and the crank provided on the periphery of the eccentric to ensure a linkage in rotation between the eccentric and the crank in the normal direction of rotation of the shaft, and to release the eccentric for rotation in relation to the crank in the opposite direction of rotation of the shaft; and means for locking the crank for rotation in relation to the support when the shaft rotates in the reverse direction to the normal direction, as well as at the start of rotation of the shaft in the normal direction, whilst the crank is free to rotate in relation to the support during the subsequent operation in the normal direction.
The prior art corresponding to such a mechanism is summed up, for example, at the beginning of the patent application FR No. 2 497 743.
The object of the invention is, above all, to make the transmission mechanisms of the kind defined above in such a way that they should meet the various practical requirements better than heretofore and in particular in such a way that they should operate more reliably and more accurately. It is, moreover, desirable that these mechanisms should be of a relatively simple design and easy to assemble. It is, moreover, desirable that the design of the mechanism should lead to silent operation.
According to a first aspect, a transmission mechanism for a windscreen wiper device in particular, of the kind previously aimed at, is characterised in that the means for locking the rotation of the crank in relation to the support comprise:
a sleeve or similar, fixed to the support and centered on the shaft, this sleeve comprising a central recess;
at least one bush freely traversed in rotation by the shaft and mounted in the central recess of the sleeve, this bush being linked in rotation with the crank,
and means for locking the bush in rotation in relation to the sleeve when the shaft rotataes in the reverse direction to the normal direction of operation, the bush being free to rotate in relation to the sleeve in the normal direction.
Advantageously, the sleeve has a radial extension at its end next to the crank, this extension being situated along the axial direction between the crank and the sleeve. The linkage in rotation of the crank and of the bush is advantageously ensured by a pin or similar member, integral with the crank and orientated substantially orthogonally to the median plane of this crank, the pin projecting towards the sleeve and passing through a radial hole provided in the said extension so that a translational motion between the crank and the bush should be permitted.
The means for locking the bush for rotation in relation to the sleeve, during the reversal of the direction of rotation of the shaft, may comprise a device with a free wheel or an equivalent device (ratchet wheel) placed between the sleeve and the bush in such a way that, for the normal direction of rotation, the bush should be free in relation to the sleeve whilst in the re
REFERENCES:
patent: 3716887 (1973-02-01), Bellware
patent: 4400844 (1983-08-01), Hayakawa et al.
patent: 4454626 (1984-06-01), Schmidt et al.
patent: 4559845 (1985-12-01), Fallows
patent: 4686733 (1987-08-01), Sahara
Eustache Jean-Pierre
Maubray Daniel
Equipements Automobiles Marchal
Lindsey Rodney M.
Smith Gary L.
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