Geometrical instruments – Miscellaneous – Light direction
Reexamination Certificate
1998-10-30
2001-09-25
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Miscellaneous
Light direction
C033S645000, C033S644000
Reexamination Certificate
active
06293021
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a process for arranging an angle graduation or angle scale at an index disk for rotational measurement systems, wherein the index disk is provided with a central opening for mounting on a carrier shaft, and further to an index disk which is produced in particular according to a process of the type mentioned above for rotational measurement systems with an angle scale arranged thereon and with a central opening for mounting on a carrier shaft.
b) Description of the Related Art
Index disks are used as scale carriers or code carriers in rotational measurement systems for measuring the rotational position of two objects moving relative to one another, e.g., for measuring angles, rotational paths or the like. For this purpose, the angle scale which is arranged on the index disk and which rotates relative to a sensing unit is sensed by the latter and the obtained sensed information is then converted by means of an evaluating unit into corresponding information, e.g., pertaining to the angle of rotation or the like. The sensing is carried out by means of suitable sensing methods, wherein photoelectric, magnetic, inductive or capacitive sensing are used in particular. Common to all of these methods, however, is the fundamental principle that the angle scale, which is generally periodic (incremental), must be centered relative to the axis of rotation of the index disk, so that the sensing information represents a measurement of the relative rotational position of the two objects moving relative to one another. In absolute angle measurement systems or in rotation sensors, information about the absolute rotational angle is generally obtained from the rotational angle information of a plurality of angle scales which are arranged concentrically on the index disk.
The achievable rotational angle measuring accuracy is decisively determined by, among others, the accuracy of the angle scale and by the deviations occurring as a result of the eccentricity of the scale relative to the support, i.e., relative to the axis of rotation of the receiving carrier shaft.
The angle scales to be arranged on the index disks can be produced economically with very high accuracy, especially for sensing based on photoelectric principles. For example, standard incremental disks with an angle indexing accuracy of less than 2 angle seconds are already available.
However, a much greater and more complex problem is that of the eccentricity of the scale relative to the support or axis of rotation of the carrier shaft. Depending on the angle measurement accuracy and angular resolution to be achieved, the use of index disks of different constructions formed of various materials is taken into consideration primarily from a cost stand point.
In this connection, very thin electroformed and photo-etched index disks are known which, while having relatively good centricity of the angle scale relative to the receiving bore, have strict limitations with respect to the angular resolution that can be achieved and are very sensitive as regards handling.
High angular resolutions and high angular resolution accuracies can be realized advantageously with glass index disks. However, these glass index disks have the disadvantage that the receiving bore can be produced at reasonable cost only with very rough tolerances, so that they cannot be used in the assembly process for centering on the carrier shaft. Therefore, specifically for purposes of centering, index disks of this kind are provided with a centering circle for adjusting the position of the index disk on the carrier shaft. This commonly used adjustment process requires special auxiliary sighting means for viewing the adjustment circle, e.g., adjusting microscopes or video cameras, and is also very time-consuming.
OBJECT AND SUMMARY OF THE INVENTION
On this basis, the primary object of the invention is to develop further a process for arranging an angle scale on an index disk for rotational measurement systems of the type mentioned above in such a way that the index disk can be manufactured economically and can be mounted simply and quickly on a carrier shaft with minor eccentricity errors of the angle scale relative to the axis of rotation of the carrier shaft in spite of coarse diameter tolerances of the carrier shaft.
According to the invention, this object is met in a process of the type mentioned above in that a clamping device is arranged in the opening of the index disk, which clamping device deforms elastically in the radial direction when the index disk is arranged on a shaft, whereupon the index disk is mounted on a reference shaft and, subsequently, the angle scale is arranged on the index disk so as to be exactly centered with respect to the center axis of the reference shaft. In this respect, a reference shaft is preferably used whose diameter corresponds to the nominal receiving diameter of the carrier shaft for which the index disk is intended.
In a surprisingly simple manner, the process according to the invention ensures that, because of the constantly uniformly acting self-centering effect which is produced by the elastic pretensioning action of the clamping device when the index disk is mounted on a shaft, the angle scale, when mounted on the index disk, is exactly centered with respect to the same axis of rotation as that with respect to which it is centered when the index disk provided with this angle scale is mounted on a carrier shaft. Due to the radially elastically deformable clamping device which is deformed when mounted on a shaft, the virtual axis of rotation which is given by the clamping device and which extends vertical to the plane of the index disk remains fixed and unaltered even when the diameter of the carrier shaft changes, wherein this holds true for a large range of tolerances of the diameter of the carrier shaft. Due to the fact that the index disk, with its clamping device which is elastically deformable in the radial direction, is initially mounted on a reference shaft and, in this state, the angle scale is then arranged on the index disk so as to be exactly centered with respect to the center axis of the reference shaft, the angle scale can be centered on the index disk in a very precise manner with respect to the center axis of this reference shaft. If the index disk provided in this way with the angle scale is mounted on a (different) carrier shaft at a later time, the self-centering effect of the clamping device again brings about an exact alignment of the angle scale arranged on the index disk with respect to the center axis of this (new) carrier shaft, so that the accuracy of the centering with which the angle scale was arranged on the index disk relative to the center point of the reference shaft is also fully maintained in this case relative to the center of rotation of the carrier shaft. The radially elastically deformable clamping device makes this possible by means of its self-centering effect which always causes the angle scale to be precisely centered with respect to the axis of rotation of the respective shaft on which the index disk is mounted, independent from the diameter tolerances of the respective shaft, during the mounting of the angle scale as well as in the mounted state.
The angle scale can be arranged on the index disk in a simple manner by a device in which the angle scale is arranged so as to be centered in a highly accurate manner with respect to the reference shaft used therein. The diameter of this reference shaft preferably corresponds to the nominal receiving diameter of the carrier shaft for which the index disk is intended in the specific case. In case of subsequent mounting, e.g., in an angle measurement device, if the index disk which has been provided with this angle scale is mounted on the receiving shaft provided in this angle measurement device, the clamping device centers the index disk again in a completely identical manner with respect to the axis of rotation of this shaft, so that the angle scale is also exact
Franz Heinz-Guenther
Freitag Hans-Joachim
Bennett G. Bradley
Johannes Heidenhain GmbH
Reed Smith LLP
LandOfFree
Process for arranging an angle scale on an index disk for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for arranging an angle scale on an index disk for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for arranging an angle scale on an index disk for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2531981