Geometrical instruments – Gauge – Having a movable contact probe
Reexamination Certificate
2001-07-18
2004-08-10
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Gauge
Having a movable contact probe
C033S551000
Reexamination Certificate
active
06772529
ABSTRACT:
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties therefor.
REFERENCE TO COMPUTER PROGRAM LISTING APPENDIX
A Computer Program Listing Appendix is hereby expressly incorporated by reference. The Computer Program Listing Appendix includes two duplicate compact discs. The files on each compact disc, their size in bytes, and the date created are:
File Name
Size
Date Created
TG82.PRG
324,990
Feb. 13, 2001
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention generally relates to an automated contact gage system using a three-axis contact contour comparator. More particularly, the invention relates to an automated contact gage system which employs a multiform contour scanner comparator which is capable of calibrating a wide range of dimensional forms/artifacts. The gage system can be employed for thread characterization (measurement), but is also capable of measuring high grade angle blocks, gage blocks, rolls, spherical forms, and virtually all manner of dimensional forms.
2. Related Art
Every fastening device owes its reliability and worth to its inherent dimensional properties. Dimensional properties can critically affect alignment properties which, in the case of certain machines or devices, can affect dynamic stability and even cause damage to or destroy the device or machine. Strength of the fastening device and the joinder accomplished by the device are important, but load distribution is also an important factor.
In the case of joinders by thread-type devices, the dimensions are embraced in the thread features which, in turn, are integral to the host cylinder. Load distribution, strength, functionality and reliability are all dependent on the dimensional properties. For example, too much load on a particular thread due to (for example) a deformed thread/cylinder can lead to shearing of that thread with obvious, detrimental consequences.
Threads are difficult to gage at the point where it counts (such as where a male device contacts a female device), so that wires have been used to make contact with both the right part of the thread and the gaging anvils. This is generally satisfactory, but it is costly and slow, making large samples impractical. Nevertheless, two or three points around the perimeter on the threads does not tell you much about the plug or the ring on which the threads are located. In addition, it tells you nothing about the load distribution properties of the device. For a comprehensive characterization of a fastener, one needs a robotized contour scanner that can gather and analyze large quantities of data in an unattended manner. With the infinitely fuller characterization afforded by a robotized scanner, one can begin to understand the fastener in question.
Although thread parameters are usually divided into major diameter, minor diameter, pitch diameter, lead, helical path, lead angle and taper, everything in between (which amounts to roundness and taper) is also important This is due to the fact that any deformation of the fastener can cause barrier thereof. Thus, the current generation of gages does not begin to meet the challenges associated with the development of modem fastening devices.
The following patents are considered to be representative of the prior art relative to the subject invention, but are burdened by various disadvantages discussed herein: U.S. Pat. No. 4,153,998 to McMurtry, entitled PROBES, issued on May 15, 1979, U.S. Pat. No. 5,822,877 to Dai, entitled MULTI-PROBE SYSTEM FOR DIMENSIONAL METROLOGY, issued on Oct. 20, 1998, U.S. Pat. No. 4,317,644 to Hosoi, entitled MACHINE TOOL PROFILING DEVICE, issued on Mar. 2, 1982, U.S. Pat. No. 4,785,545 to Aubele, entitled MEANS FOR SIMULTANEOUSLY CONNECTING A PLURALITY OF SWITCH-TYPE PROBE HEADS TO THE MEASUREMENT ARM OF A COORDINATE-MEASURING MACHINE, issued on Nov. 22, 1988, U.S. Pat. No. 5,917,181 to Yoshizumi et al., entitled PROFILE MEASURING APPARATUS, issued on Jun. 29, 1999, and U.S. Pat. No. 5,659,969 to Butler et al., entitled POSITION DETERMINING PROBE, issued on Aug. 26, 1997.
In particular, McMurtry, '998 discloses a probe for determining at what point in space contact is made between an object and a stylus. It should be noted that, in
FIG. 3
of the patent, dual bearings
9
and
10
along with an element
4
making up the probe
1
are disclosed. Similarly, Dai '877 discloses a multi-probe system for dimensional metrology in which two ball bearings
516
and
518
and an element
502
which is spherically shaped and located adjacent to the bearings
516
and
518
are disclosed. The remaining patents disclose arrangements and features quite different from those disclosed and claimed herein. In short, none of these patents discloses an automated contact gage system employing a three-axis contact contour comparator, and capable of measurement in all three dimensions, as disclosed and claimed herein.
SUMMARY OF THE INVENTION
The present invention generally relates to an automated contact gage system using a three-axis contact contour comparator.
In general, the automated contact gage system of the present invention includes a left spindle and a right spindle connected by a spindle rail, the left spindle having a stylus arm mounted on a stylus arm vertical rail for contacting the workpiece to be gaged. The automated contact gage system also includes a control section for controlling movement of the various system elements in three different dimensions (X, Y and Z), the control system including a computer, printer and associated module, storage device, and X, Y and Z motor control units.
In further accordance with the invention, the movement of the stylus arm is controlled by a three-axis contact contour comparator arrangement including a bearing arrangement for contacting the stylus arm so as to guide and support it during contact with the workpiece or device being gaged. In a preferred embodiment, the bearing arrangement includes a spherical race and bearing, the spherical race preferably comprising five spherical elements or precision balls.
The automated contact gage system of the invention is unique in that it operates in accordance with three degrees of motion along X, Y and Z axes, respectively. Each axis has its own measurement sensor, which is, preferably, a fringe interferometer/scale line hybrid device. As will be apparent from the detailed description below, the system is completely automated, and no operator intervention is necessary once the device or workpiece to be gaged is mounted on the system for calibration.
Additionally, the hardware design of the automated contact gage system of the present invention is unique relative to arrangements of the prior art and other contemporary systems in that “hard” real-environment engagement with the surface (either inner or outer) of the workpiece is achieved via a unique design of the stylus arm bearing arrangement.
In accordance with the invention, a single-element contact scanner collects virtually continuous, three-dimensional information relative to the surface of the workpiece. With the specimen mounted on the system, the stylus of the system guides the specimen into contact under selected pressure. The system of the invention is able to convert the derived three-dimensional information into test instrument (TI) dimensional characteristics with uncertainties below fifty micro-inches, and this capability results from the system's capability of self-calibrating its own measurement elements using simple, smooth, well-characterized cylinder gages.
Finally, whereas prior and current conventional contact gages are virtually incapable of measuring certain parameters, such as root width and minor diameters (particularly with respect to wind-like structures), the present invention makes it possible to measure its own stylus thickness in real time under stress caused by the test instrument itself.
As a result of the aforementioned advantages,
Fulton Christopher W.
Homer Mark
The United States of America as represented by the Secretary of
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