Geometrical instruments – Gauge – Coordinate movable probe or machine
Reexamination Certificate
1998-11-25
2002-08-13
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Gauge
Coordinate movable probe or machine
C033S558300, C033S560000, C033S572000
Reexamination Certificate
active
06430828
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improvements in coordinate positioning apparatus and particularly to such an apparatus with an indexable and/or releasable stylus.
A coordinate positioning machine includes a support for a workpiece, a stylus or other sensing device (rangefinder, vision probe, etc.) for sensing points on a workpiece, and an assembly which supports the workpiece sensing device and permits it to move relative to the workpiece along coordinate axes which, in most cases, are a horizontal x-axis, a horizontal y-axis and a vertical z-axis. Position-indicating scales are provided to indicate the position of the machine head along the coordinate axes. (The term “stylus” is used in this specification without the intention of excluding other devices for sensing points on a workpiece.)
In early coordinate measuring machines, sometimes referred to as “hard probe machines” a stylus was rigidly connected to the head of the machine. A subsequent development was the touch-trigger probe which is mounted on the head and generates a digital signal when the stylus moves due to contact with the workpiece. Still another type of probe is an analog probe which provides signals indicating the magnitude of displacements which occur between the stylus and the head of the machine. A probe of the latter type which provides such signals along three mutually perpendicular axes is disclosed in U.S. Pat. No. 5,222,034 issued to the present inventor on Jun. 22, 1993, the entirety of which is incorporated into this specification by reference.
It is customary in the metrology field to provide coordinate measuring machines with a number of interchangeable styli which are selected and used depending upon the nature of the task at hand. In some situations, the styli are mounted on the head by threaded connections. Magnetically retained styli have also been utilized, wherein two releasable coupling members are held together magnetically.
Indexable probes are known in the art as exemplified by U.S. Pat. Nos. 4,313,263, 4,571,847, and 5,185,936. In each of these systems, a probe is supported by an indexing mechanism, and a stylus is supported by the probe. In U.S. Pat. Nos. 4,313,263 and 4,571,847, indexing is achieved by engaging the stylus with a stationary object and moving the probe so that an indexable (but not releasable) coupling moves from one indexed position to another. In U.S. Pat. No. 5,185,936, the positioning elements on the probe-supporting coupling are forced apart mechanically, and a motor turns a drive dog shaft to index the coupling.
The indexing mechanisms disclosed in U.S. Pat. Nos. 4,313,263, 4,571,847, and 5,185,936. In these products, the z-rail of a machine supports styli and their respective analog or touch trigger probes. Such probes have been held on machines by releasable couplings. Due to the high cost of probes this has been very costly for machines which require the ability to perform diverse tasks. Although it is possible to support analog or touch trigger probes using the apparatus from the coupling of the present invention, it is preferred, for reasons of cost reduction, to use the coupling to connect a stylus to a probe.
Prior indexing couplings have included electrical motors which provide the angular movement for reorientation. Such motors generate heat and thus are a source of errors as they raise the temperature in localized areas of the apparatus, causing distortions which adversely affect the accuracy of any resulting measurements.
The present invention adds significantly to the versatility of a coordinate positioning apparatus in a manner which is convenient, relatively inexpensive, and without impairing the accuracy of the machine.
The present invention provides a coordinate measuring machine in which a stylus is easily and conveniently reoriented and/or removed from the machine. A preferred embodiment of the invention is disclosed in the accompanying drawings and in the following description.
Some existing coordinate measuring machines are provided with indexable analog or touch trigger probes which detect movement of a stylus relative to the probe. In such arrangements, the probes themselves have been indexable, in contrast to preferred embodiments of the present invention in which a stylus is indexable relative to the probe. When interchangeable styli are used in the prior arrangements, interchangeable probes are also required, thus adding to the expense of the apparatus because probes are expensive and multiple probes are required.
In some coordinate measuring machines, storage docks have been provided for interchangeable probes, their styli, and couplings which support the probes. Due to the shapes of these couplings and their storage docks, the couplings require a specific angular orientation in order to fit into a storage dock. These couplings sometimes carry a cluster of styli, some of which encroach into the storage spaces of adjacent storage docks. Such encroachment can be minimized by one feature of the present invention, whereby interchangeable couplings will be accepted by their storage docks at any angle. This permits the preorientation of a coupling at any angle which will minimize potential encroachment by its styli into storage docks which are adjacent to it.
One object of the invention is to provide an effective method of operating a coordinate positioning machine by utilizing an indexing dock with a mechanism and motor which are not incorporated into the probe and stylus assembly, thus simplifying such assemblies and eliminating from them the indexing motor which can create errors due to heat emitted by an indexing motor.
Another object is to reduce the cost of providing a coordinate positioning machine with stylus indexing capabilities, this objective being realized by providing only one indexing dock which can serve multiple probe and stylus assemblies, and by providing indexable couplings between the probes and their styli rather than between the machine head and the probe.
Still another object of the invention is to provide a coordinate positioning machine with a stylus storage system which is effective to store a number of stylus-carrying coupling members at orientations whereby the encroachment of their styli into the storage spaces of adjacent storage docks is reduced or eliminated.
Another object of the invention is to provide for coordinate positioning apparatus in which styli are mounted in a manner which is effective, uncomplicated, indexable, accurate, and/or capable of releasing a stylus when desired.
Other significant objects will be realized by persons familiar with the art, upon reading and understanding this specification.
SUMMARY OF THE INVENTION
In one respect, the invention involves a method for operating a coordinate positioning machine in which a stylus or other workpiece sensing device is connected to a movable member of the machine by a coupling assembly which includes first and second coupling members. The first coupling member is supported by a movable member of the machine, the second coupling member is supported by the first coupling member, and the stylus is supported by the second coupling member. The first and second coupling members respectively have first and second sets of positioning elements which are mutually engagable in a plurality of angular orientations about a coupling axis to provide a plurality of angularly indexed positions at which the second coupling member has stable and repeatable positions relative to the first coupling member. An indexing dock is provided for rotating the second coupling member about the coupling axis. The method involves the steps of moving the movable member of the machine to carry the coupling assembly and stylus or other workpiece sensing device to the indexing dock. The second coupling member is engaged with a rotatable carrier on the indexing dock, preferably after the second coupling member has been entirely disconnected from the first coupling member, and the carrier is rotated to rotate the second coupling member about the coupling axis, thus
Electronic Measuring Devices, Inc.
Gutierrez Diego
Smith R. Alexander
Smith , Gambrell & Russell, LLP
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