# US 5,703,836 A · Acoustic transducer

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- Number: US 5,703,836 A
- Document ID: US5703836A
- Status: Granted
- Kind: A
- Application number: 08/620,057
- Filed: 1996-03-21
- Granted: 1997-12-30
- Earliest claimed: 1996-03-21
- Assignees: Sandia Corporation
- Inventors: Douglas S. Drumheller
- Web page: https://patentgrep.com/patent/US5703836A

## CPC

- E21B 47/16: through the drill string or casing {, e.g. by torsional acoustic waves}
- B06B 1/0633: {Cylindrical array}
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R)

## Abstract

An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

## Claims

### Claim 1

An active acoustic transducer comprising a one-piece hollow mandrel in the form of a modified cylinder that is symmetric about a central axis into the outer surface of which mandrel is formed a recess with sides perpendicular to the central axis, said sides being separated by a first distance, and with a bottom parallel to the central axis and at a constant radial distance therefrom and within which recess are a plurality of segmented washer-shaped discs of a piezoelectric material, the washer-shaped discs having an inner radius slightly larger than the constant radial distance of the bottom of the recess and an outer radius slightly less than the top of the sides of the recess with the plurality of discs being captured between the sides of the recess in a pre-stressed interference fit.

### Claim 2 (depends on 1)

The transducer of claim 1 additionally including a power supply means electrically connected to the plurality of discs of the piezoelectric material.

### Claim 3 (depends on 1)

The transducer of claim 1 additionally including at least one washer-shaped disc of a temperature-compensating material of the same approximate radial dimensions as the discs of the piezoelectric material located within the recess and captured therewithin with the plurality of discs of the piezoelectric material in the pre-stressed interference fit.

### Claim 4 (depends on 3)

The transducer of claim 3 wherein the at least one disc of the temperature-compensating material has a thermal coefficient of expansion and a width, in total, such that the compressive stress from the pre-stressed interference fit on the plurality of discs of the piezoelectric material will remain within predetermined limits sufficient to allow the effective operation of the transducer.

### Claim 5 (depends on 3)

The transducer of claim 3 wherein the at least one disc of the temperature-compensating material is realized as two such discs, one located against one side wall and the other located against the other side wall.

### Claim 6 (depends on 1)

The transducer of claim 1 further including a protective cover plate disposed over the recess.

### Claim 7 (depends on 6)

The transducer of claim 6 wherein the protective cover plate extends past the side walls and is adapted to exclude fluids from entering into the recess.

### Claim 8 (depends on 2)

The transducer of claim 2 wherein the power supply means is located in a second recess in the mandrel.

### Claim 9 (depends on 1)

The transducer of claim 1 wherein the radius of the hollow interior region of the mandrel is sufficient to allow for the passage of hydrocarbon fluids in production quantifies.

### Claim 10 (depends on 1)

The transducer of claim 1 wherein the ends of the mandrel are adapted to connect to threaded tubing.

### Claim 11 (depends on 2)

The transducer of claim 2 further including means to communicate with a measurement device located proximate to the transducer.

### Claim 12

An active acoustic transducer comprising a one-piece hollow mandrel in the form of a modified cylinder that is symmetric about a central axis into the outer surface of which mandrel is formed a recess with sides perpendicular to the central axis, said sides being separated by a first distance, and with a bottom parallel to the central axis and at a constant radial distance therefrom and within which recess are a plurality of segmented washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material, the discs having an inner radius slightly larger than the constant radial distance of the bottom of the recess and an outer radius slightly less than the top of the sides of the recess with the discs being captured between the sides of the recess in a pre-stressed interference fit, the transducer further including a power supply electrically connected to the plurality of discs of the piezoelectric material.

### Claim 13 (depends on 12)

The transducer of claim 12 wherein the at least one disc of the temperature-compensating material has a thermal coefficient of expansion and a width, in total, such that the compressive stress from the interference fit on the plurality of discs of the piezoelectric material will remain within predetermined limits sufficient to allow the effective operation of the transducer.

### Claim 14 (depends on 12)

The transducer of claim 12 wherein the at least one disc of the temperature-compensating material is realized as two such discs, one located against one side wall and the other located against the other side wall.

### Claim 15 (depends on 12)

The transducer of claim 12 further including means to communicate with a measurement device located proximate to the transducer.