Geometrical instruments – Gauge – Collocating
Reexamination Certificate
1999-11-19
2001-07-10
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Gauge
Collocating
C033S471000, C083S435120, C083S435130, C083S435140, C083S581000, C083S468300
Reexamination Certificate
active
06256900
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to miter gauge devices for use with cutting tools and the like, and more particularly to an improved miter gauge and method for setting the miter angle with high precision.
Various cutting tools for use with either metal or wood cutting devices such as table saws, jigsaws, band saws and the like, use a miter gauge to establish the miter angle between a workpiece and the cutting blade of the device and guide the workpiece into the cutting blade at the selected miter angle. Typically, these guides consist of an elongated rectangular slide bar which slides in a similar sized groove in a flat surface of the cutting device over which the workpiece slides as it engages the cutting blade. The groove extends parallel to the cutting line of the device such that the guide line of the miter guide is parallel thereto. A slotted semi-circular frame is pivotally mounted on the slide bar and is provided with a protractor type angular indicia typically between 0° and 60° on each side of the guide line to set the desired miter angle. A combination handle and screw extends through a slot in the frame to clamp the frame at the selected angle with the slide bar. The frame includes a planar guide surface or fence which is disposed at right angles to the flat surface of the cutting device against which the workpiece is held as it is moved into the cutting blade.
These typical miter gauges are limited in accuracy due to the introduction of human error in reading the angular indicia, particularly for non standard angles in which the operator must guess the location of fractions of angles between the graduation of the angular indicia on the gauge.
Various means have been proposed in the art to increase the resolution at which the miter angle can be set including enlarging the size of the semicircular frame in order to increase the gauge indicia resolution by increasing the radius of the location of the indicia from the pivot point. Another means is disclosed in U.S. Pat. No. 4,514,909, issued May 7, 1985, for “Miter Gauge,” by Curtis R. Gilbert. In this device, the pivotally mounted frame includes a ring gear mounted atop a post at the pivot point which turns with the pivotal frame and engages a pinion gear attached to a rotatably mounted angle index dial mounted on the guide bar. The index dial is graduated to show the miter angle at which the gauge is set. The gears are operative to rotate the angle index dial through a greater angle than the miter angle by a ratio of six-to-one to increase the resolution with which the miter angle is set.
Although the rotatably mounted angle index dial may improve the accuracy in which miter angles may be set and fractions more correctly interpolated over typical gauges, the mechanism adds complication to the miter gauge and makes the gauge hard to handle due to the added gears and large angle index dial necessary to increase accuracy. Thus, it will be seen that there is a need for an improved miter gauge which is simple to operate and does not add increased size and complication to the gauge mechanism.
In view of the above need it is an object of the present invention to provide a miter gauge and method which substantially improves the resolution with which a miter angle may be set on a miter gauge without complicated additional hardware and mechanical parts.
Another object of this invention is to provide a miter gauge and method in which the resolution is increased without increasing the size of the pivotally mounted frame of the gauge on which the angular indicia is provided.
Other objects and many of the attendant advantages of the present invention will become obvious to those skilled in the art from the following detailed description taken in conjunction with the drawings.
SUMMARY OF THE INVENTION
The present invention is a miter gauge and method which provides substantially improved resolution without adding mechanical complication to the miter gauge mechanism compared to a conventional gauge configuration. The gauge includes a rectangular guide bar which slidably fits within the conventional guide groove of a cutting tool which has a flat top surface over which a workpiece slides as it is moved into the cutting blade or the like. The guide bar includes an elongated bar and is provided with an upwardly extending rear-end portion on the top surface having a first reference hole aligned with the center axis of the guide bar for receiving a first reference pin (F) which when placed in the opening in the guide bar is held at a known distance X from a pivot point on the bar. A slotted semi-circular frame is pivotally mounted to the top surface of the guide bar to pivot about the fixed pivot point on the guide bar. The guide frame includes a planar guide surface or fence which is disposed at right angles to the flat surface of the cutting device against which the workpiece is held as it is moved into the cutting blade of the tool. The slotted semi-circular frame is provided with angular indicia typically between 0° and 60° on each side of the guide line to help set the desired miter angle. A combination handle and screw extends through a slot in the frame and threadably engages the guide bar to clamp the frame at the selected angle with the guide bar. The frame further includes a rearward extending tab which supports a second, or satellite, reference pin (S) at the same radial distance X from the pivot point of the guide bar as the F pin opening in the guide bar so that as the frame is pivoted about the pivot point on the guide bar the pins F and S remain on the same radius X from the pivot point on the guide bar. The exact miter angle is then set by accurately setting the distance between the F and S pins according to the that determined for the desired miter angle.
In accordance with the method of the present invention, the radial distance X of the pins F and S from the pivot point are fixed at a value of 5 inches and the desired miter angle, which is the angle &thgr; between the lines passing from the pivot point to the pins F and S, respectively, is set on the miter gauge by determining the distance FS to be set between reference pins F and S for the desired miter angle in accordance with the relationship
FS
=10·Sine(&thgr;/2)
and setting the reference pins at this distance FS by rotating the semicircular frame about the pivot point on the guide bar while using a precision linear distance gauging device to set the desired distance between the pins FS.
It has been found that by fixing the distance X at 5 inches, the distance FS is easily determined by dividing the desired angle (&thgr;) by two (&thgr;/2), determining the sine value (y′) for the new angle (&thgr;/2) in accordance with the formula y′=Sine(&thgr;/2), moving the decimal point of the determined sine value y′ one decimal place to the right to obtain the value FS in accordance with the formula FS=y′×10, giving the above relationship:
FS
=10·Sine(&thgr;/2)
The proof for this relationship will be shown hereinbelow.
REFERENCES:
patent: 2884965 (1959-05-01), Stahl
patent: 3083744 (1963-04-01), Vold
patent: 4454793 (1984-06-01), Strong
patent: 4514909 (1985-05-01), Gilbert
patent: 4741387 (1988-05-01), Strong
patent: 4779354 (1988-10-01), Hill
patent: 5121553 (1992-06-01), Boerder
patent: 5121554 (1992-06-01), Havins
patent: 5402581 (1995-04-01), Hurd et al.
patent: 5473821 (1995-12-01), DiMarco
patent: 5491906 (1996-02-01), Reilly
patent: 5632096 (1997-05-01), Horvath
patent: 5735054 (1998-04-01), Cole
patent: 6101733 (2000-08-01), Horvath
patent: 646092 (1962-08-01), None
patent: 859739 (1962-08-01), None
Bennett G. Bradley
Poteat, P.C. Robert M.
Verbitsky Gail
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