Geometrical instruments – Gauge
Reexamination Certificate
1999-11-23
2001-10-09
Hirshfeld, Andrew H. (Department: 2859)
Geometrical instruments
Gauge
C033S642000, C033S348000, C248S904000, C248S298100
Reexamination Certificate
active
06298567
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to tram bars and, more particularly, to a tram bar and a comparator used in the environment of a metal-cutting machine, such as a milling machine. In such a machine, a work piece is supported on a moveable table and a tool or cutter is rotatably supported in a collet or chuck. In accordance with the present invention, an improved tram bar is mounted in place of the cutting tool and allows a machine operator to inspect the workpiece with a minimum of time and effort.
BACKGROUND OF THE INVENTION
While operating on a workpiece using a conventional metal-cutting machine, such as a milling machine, where the workpiece is clamped to a work table, a dial indicator is periodically mounted in the chuck to gage its various surfaces. The operator must then maneuver the work table to move the workpiece into various desired positions with respect to his work station and to the milling machine axis. The quality or accuracy of the finished product depends on the accuracy with which the dial indicator is used to position the workpiece with respect to the machine axis.
The desired position of the workpiece is first approximated by the operator without the aid of any inspection device. A dial indicator is then inserted into the chuck and used according to known procedures to precisely adjust the location of the workpiece. An existing feature of the workpiece, such as a pilot hole, a slot or workpiece face, is typically used as a reference when positioning the workpiece. For instance, a workpiece may be centered on the machine axis using a dial indicator to compare sides of an existing hole to one another and the machine axis. The dial indicator may be mounted to a crossbar or one leg of an L-shaped bar to provide a convenient way of swinging the indicator through 360 degrees to compare different faces of the workpiece to one another at various radial distances from the machine axis. Prior art procedures, however, are cumbersome and time-consuming, regardless of whether the machine is a standard, manually-operated milling machine, or an automatic machine, such as a computer numeric control (CNC) machine.
The operator uses one hand to turn the machine tool chuck and the indicator mounted therein. The other hand is used to control movement of the machine table. With practice, both hands can be manipulated simultaneously to position the work table and rotate the chuck. However, during this procedure, when the dial indicator is rotated so that its dial face cannot be seen by the operator, the dial indicator cannot simply be rotated for viewing by the operator. The dial indicator must remain undisturbed in relation to the machining axis while measuring a workpiece. Instead, the operator will generally relinquish control of the work table and use one hand to manipulate a hand-held mirror so he can view the dial face while the other hand rotates the chuck.
When the dial indicator is mounted to a crossbar, which allows large workpieces to be measured, the dial indicator may physically interfere with the chuck when the indicator is positioned near the machine axis. This occurs when a feature such as a small hole is being measured and the indicator must be tilted in order to reach the feature near the axis. To avoid interference, the indicator is typically moved outwardly along the crossbar and tilted even further toward the machine axis so the small hole can be measured. By tilting the indicator, however, the dial face is left at an obscure angle and is for the operator difficult to view.
A clamp adapter is generally required to fasten the dial indicator to the tram bar. Prior art clamp adapters, however, are typically configured to receive only one size of dial indicator mount shaft, so each dial indicator must have its own clamp adapter. This results in increased cost to the operator, and increased time spent changing adapters.
A tram bar is needed which facilitates the use of various sizes of dial indicators, and reduces the number of manual tasks which the operator must perform while aligning and measuring a workpiece on a metal-forming machine. The present invention is drawn toward such an inspection device.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a tram bar that can effectively and easily measure features of a workpiece at any radial distance from, or angular relationship to, the machining axis within its reach.
Another object of the present invention is to provide a tram bar which can secure various sizes of indicator mount shafts.
Yet another object of the present invention is to eliminate the need for a hand-held mirror to view a dial indicator face resting in certain orientations.
In accordance with the present invention, a tram bar is provided in a metal-cutting machine, such as a milling machine, where a workpiece is supported on a work table, and wherein a cutting tool is normally provided on a machine axis in a rotatable support above the work table. In place of the cutting tool, the present invention contemplates inserting a spindle into the collet or chuck and providing a crossbar on the spindle so that the crossbar can be adjusted transversely of the machine axis. The crossbar has one end which is bent at an angle and provided with a clamp adapter. A dial indicator is adjustably secured to the clamp adapter so that the dial indicator can be articulated to rest in a plane generally parallel to the machine axis. A second end of the crossbar mounts a reflective mirror so that the dial indicator can be read when facing away from the operator.
One feature of the tram bar is the bent crossbar which allows the dial indicator to be articulated to an easily-viewed position when measuring a workpiece feature near the machine axis.
Another feature of the tram bar is a wedge-shaped receiving bore of the clamp adapter which mounts various sizes of indicator mount shafts.
An advantage of the present invention is that the tram bar can be used to easily measure a workpiece feature when the dial indicator faces away from the operator.
REFERENCES:
patent: 1953614 (1934-04-01), King
patent: 2456003 (1948-12-01), Knutson
patent: 2625746 (1953-01-01), Rudhart
patent: 2721390 (1955-10-01), Pasturczak
patent: 3180030 (1965-04-01), Witzke
patent: 3214839 (1965-11-01), Cunningham
patent: 4896857 (1990-01-01), McCullough
patent: 5036595 (1991-08-01), Nevery
Hirshfeld Andrew H.
McCormick Paulding & Huber LLP
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