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Scale for a Positioning Table

IP.com Disclosure Number: IPCOM000094576D
Original Publication Date: 1965-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Hoernes, GE: AUTHOR

Abstract

This scale is used to determine the position between a stationary member and a moveable member, for example, a table which carries the work piece in an automatic machine tool. Driven part 10 extends over the entire length of travel of the table whose position is to be measured. A slide comprised of a short piece 12 is capacitively coupled to part 10. Teeth 14 of part 10 are connected to conductors 16. The output of oscillator 18 is amplified by amplifier 20, the output of which feeds phase splitter 22. The output 24 of phase splitter 22 is in phase with oscillator 18. The output 26 is equal to the oscillator frequency F plus 180 degrees.

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Scale for a Positioning Table

This scale is used to determine the position between a stationary member and a moveable member, for example, a table which carries the work piece in an automatic machine tool. Driven part 10 extends over the entire length of travel of the table whose position is to be measured. A slide comprised of a short piece 12 is capacitively coupled to part 10. Teeth 14 of part 10 are connected to conductors 16. The output of oscillator 18 is amplified by amplifier 20, the output of which feeds phase splitter 22. The output 24 of phase splitter 22 is in phase with oscillator 18. The output 26 is equal to the oscillator frequency F plus 180 degrees.

The amplified oscillator output is shifted 90 degrees by phase shifter 28, the output of which is split by phase splitter 30 into two signals 32 and 34. These are, respectively, F + 90 degrees and F + 270 degrees. The phase-shifted signals are applied to conductors 16. Thus, each tooth 14 is energized by a signal shifted 90 degrees in phase from the signal applied to the adjacent teeth. The teeth 36 of slide 12 are spaced a distance D apart so that at all times the teeth 36 are over the teeth 14 having the same phase.

Assume that the slide 12 is located exactly over phase F + 90 degrees, the second tooth from the top of the drawing. The largest capacitance is then at phase F + 90 degrees, but there is also some pickup from the two neighboring signals F and F + 180 degrees. Because the arrangement is...