Geometrical instruments – Miscellaneous – Light direction
Reexamination Certificate
1999-07-15
2001-08-21
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Miscellaneous
Light direction
C033S813000
Reexamination Certificate
active
06276066
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a positioning device with a mechanism for converting rotary motion into a linear motion, and more particularly, such a positioning device with a coarse adjustment and a fine adjustment.
2. Discussion of Relevant Art
German Patent DE 195 16 643 C1 describes a hardness testing equipment with an extending ram having a force measurement device at its tip. The ram can be moved in a two-stage manner by a combination with a spindle and a piezo positioner. The displacement movement can then be uncoupled by means of a spindle nut and a longitudinal guide integrated into the device. A movement of the piezo positioner is superposed on the movement of the spindle nut, in that the piezo positioner is coupled e.g. coaxially with the spindle nut. In this equipment, only the total stroke can be measured, and thus the reference surface is not clear. A measurement of a difference of the movement of the piezo positioner relative to the spindle nut is not provided. Since piezo elements operate with hysteresis, the deflection state of the piezo positioner therefore cannot be exactly given, particularly when a fine adjustment in the range of motion of e.g. 100&mgr; is provided. A positioning movement takes place only in the axial direction. Since the equipment ends in a measuring tip for axial reaction forces, no transverse forces, which can arise from tilting of the sensed surface, need be taken up. Moreover, no alternating directions of motion are provided in the prior art equipment.
Japanese Laid-Open Patent Publication JP-A-8-313785 shows a microscope focusing drive with a conventional rack drive and a subsequent piezo element.
SUMMARY OF THE INVENTION
In contrast, the present invention has as its object to provide a positioning device of the kind mentioned at the beginning, which functions with high accuracy and indeed also when tilting has to be taken into account.
According to the invention, this object is achieved by a positioning device comprising: an object seating, a spindle, a spindle nut cooperating with said spindle for conversion of a rotary motion into linear motion for a coarse adjustment, a piezoelectric linear positioning element for fine adjustment arranged in series with said spindle and said spindle nut, and a joint arranged between said object seating and said spindle, which relieves said piezoelectric linear positioning element of transverse forces and moments.
By means of the joints, in particular cardan joints, the piezoelectric linear positioning element is loaded only in the axial displacement direction. This means that except for axial forces, all other forces are uncoupled from the spindle. By virtue of the invention, the load effect always takes place centrally, including, for example, when the positioning device is provided for a plate. Thus transverse forces that could damage the piezoelectric linear positioning element are prevented with certainty.
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patent: 38 12 684 A1 (1988-04-01), None
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Patent Abstract of Japan, Publication No. 63153405; dated Jul. 14, 1987, Inventor: Mikoshiba Nobuo.
Hof Albrecht
Scheibl Lothar
Carl-Zeiss-Stiftung
Gonzalez Madeline
Gutierrez Diego
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