Data processing: measuring – calibrating – or testing – Measurement system – Dimensional determination
Reexamination Certificate
1999-03-01
2001-09-04
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Dimensional determination
C033S503000
Reexamination Certificate
active
06285965
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a process for measuring taper threads on a coordinate measurement device which is outfitted with a table adjustable in the X, Y and Z coordinates for receiving a specimen provided with the taper thread and which further comprises a feeler probe which is held at a spring clip such that its position is adjustable in the Z direction and which is connected by this spring clip with a measurement sleeve which is adjustable in the X direction and at which is arranged a sensing element which can be deflected in the X coordinate, wherein a calibration of the feeler probe is initially carried out with reference to a setting gage, wherein, after calibration, the sensing element is brought into contact with different thread flanks one after the other for the purpose of measuring the taper thread, the measurement values determined in this way are stored in an evaluating unit and the characteristic values and fundamental quantities of the taper thread are calculated on the basis of the stored measurement values.
b) Description of the Related Art
The invention is especially suited for determining the flank diameter of taper threads. The flank diameter is determined in a testing plane which is at a determined distance from an end face of the specimen; DIN 158 (metric tapered external thread) and DIN 2999 (Withworth pipe thread), among others, are taken into account.
DIN 158 and DIN 2999 set forth the characteristic values and fundamental quantities for tapered external thread and, at the same time, provide directions for a simple and direct functional testing of this thread. Suggestions are made for the construction and handling of gages by which the fundamental quantities of a taper thread can be tested. For this purpose, there are provided taper thread ring gages or thread plug gages which only enable testing of the thread, but not measurement of the thread.
For example, the flank diameter of a taper thread can be determined in that a plug gage with a cylindrical thread is screwed into a tapered internal thread; the value of the flank diameter must then be derived from the screw-in depth in a corresponding measurement plane. The flank diameter cannot be exactly determined in this way.
Further, it is known to use the three-wire method, as it is called, to measure tapered external threads. This method is described, for example, in Langsdorf, “Messen von Gewinde [Measurement of Thread]”, Springer-Verlag Berlin, Heidelberg, New York, 1974, pages 69 to 74, and in Zill, “Messen and Lehren im Maschinen-und Feingerätebau [Measurement and Gaging in Mechanical and Precision Instrument Engineering]”, Deupner Verlagsgesellschaft, Leipzig 1956, pages 183 and 184.
This measurement process has the disadvantage of being quite time-consuming because, in addition to the thread measuring wire set, it requires thread measurement balls of identical diameter and associated centering sleeves which must be fitted to the complementing spindle.
A process and an arrangement for measuring taper thread on a coordinate measurement device is known from DE-PS 44 10 195.3. In this case, after a measurement feeler has been calibrated, the specimen is clamped on the coordinate table by means of a calibrating ring. The table is tiltable and is initially adjusted in such a way that a first flank diameter line of the taper thread is oriented parallel to the Z coordinate. In this position, the thread is sensed repeatedly in different Z coordinates. The inclination of the table is subsequently changed in such a way that a second flank diameter line located diametrically opposite to the first flank diameter line is oriented parallel to the Z coordinate. In this case, also, the thread turns are sensed repeatedly in different Z positions. Measurement values are determined for every instance of sensing and are stored in an evaluating device. The characteristic values and fundamental quantities of the taper thread are determined from the stored measurement values based on known geometric relationships. A disadvantage in this process consists in that the table must be tiltable, which requires an additional articulation axis for its bearing support and, to this extent, involves the risk of inaccuracy due to manufacturing tolerances.
A process and a device for the measurement of tapered external thread are known from the German Patent 195 22 276 C1. In this case, a single-coordinate measurement device is provided for carrying out the process, wherein the specimen with the thread to be measured is received on a slide which is adjustable in three coordinate axes and is sensed by a feeler probe arranged at the measurement sleeve of the single-coordinate measurement device. It is disadvantageous that the process and device described above are not suitable for the measurement of internal thread.
OBJECT AND SUMMARY OF THE INVENTION
It is the primary object of the invention to further develop the known process for measuring taper threads on a coordinate measurement device in such a way that fundamental quantities of external taper thread and internal taper thread can be determined precisely and effectively.
This object is met for the measurement of taper threads according to a process of the type described above in that the spring clip is initially tared in a first step following the calibration in such a way that two coincidence marks which are associated with the Z coordinate, wherein one coincidence mark is arranged so as to be movable with the spring clip in the Z coordinate and the other coincidence mark is arranged so as to be stationary, are offset relative to one another in the Z direction, i.e., after taring, the distance between the movable coincidence mark and the table support surface should be less than the distance between the stationary coincidence mark and the table support surface.
A reference plane is then defined in a second step. For this purpose, the table is adjusted in the Z direction until the table support surface contacts the sensing element and the table, carrying the sensing element and spring clip along with it, is advanced further in the Z direction until the two coincidence marks coincide; the Z value of the table position which has accordingly been reached is stored as a reference valve z
A
or the Z position that has been reached is set at 0, so that it is easy to adjust to this table position again. The table support surface accordingly represents the reference plane for the measurement as soon as the table position reaches the reference value z
A
.
In a subsequent, third step, the table is moved back from the sensing element until there is sufficient distance between the table support surface and the sensing element for placement of the specimen on the table support surface. After the specimen is placed, a thread turn is sensed by the sensing element in that the measurement sleeve is displaced in the X direction and the sensing element is adjusted to the arrest point or reversal point at the specimen circumference by displacing the table in the Y direction. The table is subsequently adjusted in the Z direction until the coincidence marks coincide on the spring clip.
After this, in a fourth step, the measurement sleeve is displaced further in the X direction until the sensing element has reached its zero position; in this position, a first value pair x
1
, z
1
is read off and stored, wherein x
1
is the display value at the measurement sleeve (in the x direction) and z
1
is the table position in the Z coordinate.
In a fifth step, another thread turn is now sensed on the same diameter side of the taper thread and a second pair of values x
2
, z
2
is similarly read off and stored.
Subsequently, in a sixth step, further value pairs x
3
, z
3
and x
4
, Z
4
are obtained from the diametrically opposite diameter side. In the following seventh step, the flank diameter of the taper thread and, if necessary, the taper angle error are determined by means of the evaluating unit based on the geometric relationships o
Hoff Marc S.
Optische Koordinatenmesstechnik GmbH
Raymond Edward
Reed Smith LLP
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