Supports – Mirror or picture type – Bracket
Patent
1997-07-07
1999-08-03
Berger, Derek J.
Supports
Mirror or picture type
Bracket
74 8915, 359874, 188 77W, 464 30, 464 40, A47G 124, F16D 702, F16D 5100, F16H 2702
Patent
active
059314389
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
The invention relates to a displacement adjustment device for at least partly converting a rotation into a translation. More in particular, the invertion can relate to a displacement adjustment device, comprising two parts capable of carrying out both a rotation movement and a linear displacement relative to each other, one part being provided with a screw thread, and coupling means being provided for coupling the other part to this screw thread.
Such a device is known in practice for effecting a linear movement by means of a motor. An example of an application of such a device is in a mirror adjusting instrument. When for instance a wing mirror of a vehicle comprises such an instrument, it is easy for the driver to remotely adjust the position of the mirror plate of that wing mirror.
In an elementary embodiment, a known displacement adjustment device has a rotatable gear wheel provided with an internal screw thread, and a bar extending therethrough and provided with an external screw thread which engages with this internal screw thread. The bar is attached to an object to be adjusted, for instance a support plate for a mirror plate of a wing mirror, in such a manner that this bar cannot rotate. When the gear wheel is driven for rotation, the non-rotatable bar is forced to move linearly along its longitudinal axis.
This elementary embodiment has a number of imperfections. In the first place, it may happen that some kind of obstacle restrains the displacement of the bar, such as for intance an end stop. When a driving motor is then energized, it will be unable to rotate, which involves the risk of the motor burning out. In the second place, for some applications it is desired or even necessary that the object to be adjusted can also be adjusted by hand, for instance to enable it to yield to an unanticipated load from outside, but also to permit carrying out an adjustment even in the event of electric failures, which, for reasons of safety, is important in particular with the above-mentioned example of a wing mirror. In the above-mentioned elementary embodiment, such a manual adjustment is not possible.
In order to overcome these imperfections in the elementary embodiment, it is provided with means for enabling a temporary uncoupling. In this connection, the internal screw thread of the rotatable gear wheel is subdivided into a number of segments, which segments are attached to that gear wheel for radial spring action. When an axial force is exerted on those segments, for instance by one of the above-mentioned causes, those segments will be radially forced outwards and thus be released from the engagement with the external screw thread of the bar. Upon further rotation of the gear wheel or further displacement of the bar, the segments will engage with the external screw thread of the bar again, but then shifted by one helix.
Although the elementary embodiment thus modified indeed solves the above-mentioned imperfections, it nevertheless involves some drawbacks.
The first drawback concerns the fact that this construction produces a loud rattling noise, when the object to be displaced reaches an end stop, as well as when the object to be displaced is adjusted manually.
A second drawback concerns the fact that wear occurs, caused by the rattling displacement of the internal screw thread segments over the external screw thread of the bar.
A third drawback, which is in particular involved in the application in a mirror adjusting instrument, is that the object (mirror plate) to be displaced cannot be adjusted continuously (in stepless fashion), but can only reach positions defined by the pitch of the external screw thread of the bar.
A fourth drawback concerns the fact that when the object to be displaced is manually adjusted in a first direction, the required force generally differs from, the force necessary f
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Berger Derek J.
IKU Holding Montfoort B.V.
Johnston Roger A.
Nornberg Michael
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