Digital Rule

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The current invention is an improvement in basic measuring instruments. Like my other disclosure " Optical Illuminated Rule, " it is especially suited to the visually challenged. As with my other design the linear divisions are every 1/16". The uncluttered divisions make it easy to read. Despite the fact that the scale is in 1/16" divisions, it is possible to interpolate measurements to 1/64" without being taxing on the eyes.

The invention consists of a series of kerfs. The kerfs are spaced precisely 1/16" apart and the width of the slot is exactly 1/32". For a millimeter scale, a 1 mm slot every 2 mm is utilized. The invention resembles a comb in appearance.The scale can be read under all lighting and does not suffer from an optical null. As with any scale the measurement is read by observing the line that most closely aligns with the part. It is understood that the measurement is to the center of the division (kerf). The kerf may terminate in a V to facilitate reading this. On a conventional scale, fine closely spaced lines are hard to resolve if you don't have good eyesight. It will be noted that the kerfs act as a window. When overlayed on a work-piece, the part either extends into the window or it doesn't . Back lighting makes this apparent. If the part bisects the kerf, the measurement is the nominal dimension read. If the part is at the edge of the window the measurement is .015" less than the division read. If the part extends over to the other edge of the window, then the reading is +.015" larger. If the window is completely obscured and the work extends midway into the next tooth, then the reading is +.032". With good eyes it is possible to interpolate to 1/4 intrusion into the kerf. This equates to a resolution of .007" without the clutter and confusion of additional fine lines.

The preferred material is hard coat anodized Aluminum. A detachable datum piece may be secured to 1 end and it houses a knurled scribe secured by an o-ring in a counter-bored hole. The user can layout lines on a workpiece by banking the datum piece against the edge of the work and fitting the closely sized scribe in the desired kerf. As only a kerfed dimension can be marked- this represents the "digital" nature of the scale. It will be noted however, that the lines may be scribed with an accuracy of +/-.001, utilizing a "pocket scale" without the need for exceptional eyesight. This rivals a height gage in accuracy!

The rule can be produced economically by possibly fine blanking or gang saw cutting multiple units on a horizontal mill, thus producing dozens of parts with a single pass of the tool.The units are then laser marked or photo chemically etched. A T- slotted piece may also be employed to act as a caliper.

Upon acceptance by the marketplace, a patent will be filed within the year.


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  • Name:
    Randy Andronica
  • Type of entry:
  • Patent status: