Electricity: motive power systems – Periodic – repetitious or successive operations control of...
Patent
1981-09-04
1982-09-21
Weldon, Ulysses
Electricity: motive power systems
Periodic, repetitious or successive operations control of...
318DIG2, 318466, H02P 104
Patent
active
043509380
DESCRIPTION:
BRIEF SUMMARY
It is known that most window wiper drive mechanisms, in particular for motor vehicles, are provided with travel limit stop devices which permit the window wiper blade to be returned to a pre-determined rest position off the window surface to be wiped. Such a drive mechanism in most cases comprises a motor of permanent magnet inductor type, which is connected to a speed reducing unit comprising an endless worm whose threads engage with a toothed wheel carried by a shaft at right angles to the shaft of the worm. The reducing unit is housed within a sealed casing which is closed by a cover disposed facing the reducing wheel.
In a known embodiment, the travel limit stop device comprises a connector fixed to the front surface of the reducing wheel, the conductor sectors of which co-operate with three independent sliding contacts which are positioned and fixed on the cover of the casing. Each sliding contact comprises an elastically deformable curved metal blade whose free end carries a contact point which is fitted thereto and which slidingly co-operates with one of the three concentric circular tracks carried by the connector. The three sliding contacts are at different potentials, since one is connected to the supply circuit of the motor, the other is connected to the induction armature of the motor by a control switch and the third to ground.
A travel limit stop device of this kind becomes difficult to construct, from the mechanical point of view, when the motor reducing unit is to be miniaturised. In fact, the size of the connector is linked to the diameter of the reducing wheel which carries it so that a reduction in the size of the reducing wheel results in a reduction in the diameter of the connector and consequently results in the three sliding contacts which describe the three concentric circular tracks of the connector coming closer together. Now, the three sliding contacts are independent components which become particularly difficult to position relative to each other by virtue of the close tolerances which result from their coming closer together. In addition, the limit device is generally provided to operate irrespective of the direction of rotation of the motor or the reducing wheel. Accordingly, it is necessary to provide for two different arrangements in respect of the sliding contact carrier member on the cover of the casing, in order to take into account the direction of rotation of the reducing wheel, that is to say, two openings for receiving the sliding contact carrier member. It will be appreciated that the opening which is not in use is closed by a plug fitted thereto, as otherwise the casing of the reducing unit would no longer be sealed, as is required.
The aim of the present invention is to overcome the above-indicated disadvantages and for this purpose the invention proposes providing a travel limit stop means wherein the above-indicated connector-sliding contact system has been reversed. According to the invention, the connector is formed by three independent conductor sectors fixed to the cover of the casing and the sliding contacts which are electrically connected are carried by the reducing wheel. Advantageously, the three conductor sectors of the connector are disposed along two circular concentric tracks, the number of sliding contacts then being reduced by one unit and the two remaining sliding contacts being formed by the two teeth of a fork-shaped member carried by the reducing wheel. The device according to the invention therefore permits the omission of one sliding contact and consequently a contact point fitted thereto, and at the same time solves the problem of relative positioning of the sliding contacts, as the two remaining sliding contacts are formed from one piece which acts as a double-contact electrical connecting bridge member. The outside diameter of the connector may be greater than that of the reducing wheel, in contrast to the connector of known type wherein the outer diameter was necessarily less than that of the wheel on which it was fixed. Besides the savi
REFERENCES:
patent: 2777907 (1957-01-01), Hooker
patent: 3030460 (1962-04-01), Huetten et al.
patent: 3095597 (1963-07-01), Waldron
patent: 3483459 (1969-12-01), Kearns
Equipements Automobiles Marchal
Weldon Ulysses
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