# US 4,399,958 A · Tape loop position detector

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- Number: US 4,399,958 A
- Document ID: US4399958A
- Status: Granted
- Kind: A
- Application number: 06/271,573
- Filed: 1981-08-08
- Granted: 1983-08-23
- Earliest claimed: 1980-06-19
- Assignees: Compagnie Internationale pour l'Informatique Cii-Honeywell Bull
- Inventors: Jean Dupont
- Web page: https://patentgrep.com/patent/US4399958A

## CPC

- G01B 7/003: {for measuring position, not involving coordinate determination (coordinate measuring G01B7/004)}
- G01D 5/2417: {by varying separation}
- G11B 15/58: with vacuum column
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

The position of a tape loop in a vacuum chamber is capacitively detected. e capacitive detector includes a flexible electrode that is deflected between a pair of walls parallel to a wall of a vacuum chamber in which the loop is formed by differential pressure in the chamber and by the pressure of a vacuum source having a pressure between the two pressures in the vacuum chamber. Between the flexible electrode and a stationary electrode is a fixed, solid dielectric. The wall includes plural apertures forming separate fluid flow paths. The vacuum source includes a partition with a plurality of apertures forming separate fluid flow paths. The apertures of the wall and partition are aligned and positioned in a direction between opposite ends of the vacuum chamber. The vacuum chamber wall is electrically grounded and an electrical insulator is positioned between an end of the flexible electrode adjacent the wall to maintain the flexible electrode electrically insulated from and a different potential from the grounded wall.

## Claims

### Claim 1

Apparatus for detecting the position of a tape loop in a chamber, the tape being supplied to one end of the chamber, the other end of the chamber being maintained at a fluid pressure less than the one end and being closed by the tape in the chamber, a portion of the chamber where the loop is located including a wall for providing a fluid flow relation between the chamber and the detecting apparatus, the detecting apparatus being responsive to the location of a fluid pressure transition in the chamber resulting from the position of the loop and the fluid pressure difference on opposite sides of the loop, the detecting apparatus comprising a variable capacitor having fixed and flexible electrodes spaced from each other, the fixed electrode being spaced from and parallel to the wall, a stationary solid dielectric positioned between the electrodes, the stationary solid dielectric extending between the electrodes through substantially the same distance as the electrodes, a vacuum source for applying a fluid pressure to the flexible electrode between the pressures at the one and other ends of the chamber, first and second opposite ends of the flexible electrode having faces respectively positioned in first and second planes substantially parallel to the wall, the face in the second plane being on the stationary solid dielectric, the flexible electrode and vacuum source being arranged so that the position of a transition of the flexible electrode from the wall to the region is dependent on the position of the loop in the chamber, whereby a portion of the flexible electrode between the pressures of the one end and of the vacuum source is urged by the higher pressure of the one end against the stationary solid dielectric and a segment of the flexible electrode between the pressures of the other end and the vacuum source is urged by the higher pressure of the vacuum source against the wall.

### Claim 2 (depends on 1)

The apparatus of claim 1 wherein the wall includes a plurality of apertures forming separate fluid flow paths, the vacuum source including a partition with a plurality of apertures forming separate fluid flow paths, the apertures positioned in a direction between the one and another ends of the chamber.

### Claim 3 (depends on 1, 2)

The apparatus of claim 1 or 2 wherein the wall is electrically grounded and the moveable electrode is electrically insulated from and at a different potential from the grounded wall.

### Claim 4 (depends on 1, 2)

The apparatus of claim 1 or 2 further including a grounded shielding ring positioned adjacent the fixed electrode and remote from the flexible electrode for preventing stray ground currents from being coupled to the electrodes.

### Claim 5 (depends on 1, 2)

The apparatus of claim 1 or 2 wherein the wall is electrically grounded and the moveable electrode is electrically insulated from and at a different potential from the grounded wall, and a shielding ring positioned adjacent the fixed electrode and remote from the flexible electrode for preventing stray ground currents from being coupled to the electrodes.

### Claim 6

Apparatus for detecting the position of a tape loop in a chamber, the tape being supplied to one end of the chamber, the other end of the chamber being maintained at a fluid pressure less than the one end and being closed by the tape in the chamber, a portion of the chamber where the loop is located including a wall having a plurality of apertures forming separate fluid flow paths between the chamber and the detecting apparatus, the detecting apparatus being responsive to the location of a fluid pressure transition in the chamber resulting from the position of the loop and the fluid pressure difference on opposite sides of the loop, the detecting apparatus comprising a variable capacitor having fixed and flexible electrodes spaced from each other, the fixed electrode being spaced from the wall, the flexible electrode including a flexible strip consisting of metal, a dielectric region positioned between the electrodes, a vacuum source for applying a fluid pressure to the flexible electrode between the pressures at the one and other ends of the chamber, the vacuum source including a partition with a plurality of apertures forming separate fluid flow paths, first and second opposite ends of the flexible electrode having faces respectively positioned in first and second planes substantially parallel to the wall, the face of the flexible electrode in the second plane being on the partition, the flexible electrode and vacuum source being arranged so that the position of a transition of the flexible electrode from the wall to the partition is dependent on the position of the loop in the chamber, whereby a portion of the flexible electrode between the pressures of the one end and of the vacuum source is urged by the higher pressure of the one end against the partition and a segment of the other end and the vacuum source is urged by the higher pressure of the vacuum source against the wall.

### Claim 7 (depends on 6)

The apparatus of claim 6 wherein the apertures of the wall and partition are aligned.

### Claim 8 (depends on 6, 7)

The apparatus of claim 6 or 7 wherein adjacent ones of the apertures are positioned in a direction between the one and an other ends of the chamber.

### Claim 9 (depends on 6, 7)

The apparatus of claim 6 or 7 wherein the dielectric region is a stationary solid.

### Claim 10 (depends on 6, 7)

The apparatus of claim 6 or 7 wherein the dielectric region is a stationary solid mounted on a printed circuit board carrying the stationary electrode.

### Claim 11 (depends on 6, 7)

The apparatus of claim 6 or 7 wherein the wall is electrically grounded and the moveable electrode is electrically insulated from and at a different potential from the grounded wall.

### Claim 12 (depends on 11)

The apparatus of claim 11 further including a grounded shielding ring positioned adjacent the fixed electrode and remote from the flexible electrode for preventing stray ground currents from being coupled to the electrodes.

### Claim 13

Apparatus for detecting the position of a tape loop in a chamber, the tape being supplied to one end of the chamber, the other end of the chamber being maintained at a fluid pressure less than the one end and being closed by the tape in the chamber, a portion of the chamber where the loop is located including an electrically grounded wall for providing a fluid flow relation between the chamber and the detecting apparatus, the detecting apparatus being responsive to the location of a fluid pressure transition in the chamber resulting from the position of the loop and the fluid pressure difference on opposite sides of the loop, the detecting apparatus comprising a variable capacitor having fixed and flexible electrodes spaced from each other, the fixed electrode being spaced from the wall, a stationary solid dielectric positioned between the electrodes, a vacuum source for applying a fluid pressure to the flexible electrode between the pressures at the one and other ends of the chamber, first and second opposite ends of the flexible electrode having faces respectively positioned in first and second planes substantially parallel to the wall, the face in the second plane being on the dielectric, an electrical insulator between the first end and the wall for maintaining the flexible electrode electrically insulated from and at a different potential from the grounded wall, the flexible electrode and vacuum source being arranged so that the position of a transition of the flexible electrode from the wall to the region is dependent on the position of the loop in the chamber, whereby a portion of the flexible electrode between the pressures of the one end and of the vacuum source is urged by the higher pressure of the one end against the region and a segment of the flexible electrode between the pressures of the other end and the vacuum source is urged by the higher pressure of the vacuum source against the wall.

### Claim 14 (depends on 13)

The apparatus of claim 13 further including a grounded shielding ring positioned adjacent the fixed electrode and remote from the flexible electrode for preventing stray ground currents from being coupled to the electrodes.

### Claim 15 (depends on 1, 2, 6, 7, 13)

The apparatus of claim 1, 2, 6, 7 or 13 wherein the variable capacitor is connected in an electric circuit for deriving an output signal having an amplitude commensurate with the position of the loop, said circuit including an a.c. source for supplying opposite polarity current pulses to the variable capacitor and a second capacitor, a rectifier including an integrating capacitor responsive to the sum of the currents flowing in the variable and second capacitors, for deriving a bi-polarity d.c. signal commensurate with the position of the loop, the d.c. signal having a zero value in response to the loop being centrally positioned relative to the wall, as well as positive and negative values in response to the loop being respectively positioned on first and second opposite sides of the central position.

### Claim 16 (depends on 1)

The apparatus of claim 1 wherein the flexible electrode includes a flexible strip consisting of metal.