Ultrasonic transducer with a sealed 3D-printed mini-horn array

1. An ultrasonic flow meter, comprising:

a meter body;

a passage in the meter body for conducting flow of a fluid stream that is to be metered;

a pair of ultrasonic transducers coupled to the meter body, the transducers configured to form a chordal path across the passage between the transducers, each transducer comprising:

a transducer housing;

a piezoelectric crystal disposed within the transducer housing; and

a mini-horn array coupled to the transducer housing, the mini-horn array comprising:

an opening-free enclosure;

a closed cavity inside the enclosure, the cavity having a proximal end surface and a distal end surface; and

a plurality of horns enclosed within the closed cavity, wherein the horns include a horn base portion adjacent to the proximal end surface of the cavity and a horn neck portion that extends from the horn base portion in a direction away from the piezoelectric crystal and towards the distal end surface of the cavity, wherein the horn neck portions are separated by spaces within the cavity.

2. The ultrasonic flow meter of claim 1 further comprising powder in the cavity between the horns.

3. The ultrasonic flow meter of claim 2 wherein the enclosure comprises a first material and wherein the powder comprises the first material in a powdered form.

4. The ultrasonic flow meter of claim 1 wherein the powder fills the spaces between the horns in the cavity.

5. The ultrasonic flow meter of claim 4 wherein the enclosure comprises a first material and wherein the powder comprises the first material in a powdered form.

6. The ultrasonic flow meter of claim 1 wherein the mini-horn array is made by a 3D printing technique.

7. The ultrasonic flow meter of claim 6 wherein the opening-free enclosure is sealed by the 3D printing technique.

8. The ultrasonic flow meter of claim 6 wherein the housing comprises a tubular stalk, a front cap at a leading end of the stalk, and a transducer retainer coupled at the trailing end of the stalk; and

wherein the front cap includes a tubular body and

wherein the mini-horn array is formed directly on the tubular body by 3D printing.

9. A method of making an ultrasonic transducer comprising:

using a 3D printing technique, building a mini-horn array such that the mini-horn array includes horns disposed in an opening-free enclosure and

attaching the mini-horn array to a transducer housing that is configured to house a piezoelectric crystal.

10. The method of claim 9 wherein using the 3D printing technique and attaching the mini-horn array to the transducer housing comprise:

applying a first layer of a powder to the transducer housing;

causing a portion of the first layer of the powder to solidify and bond to the transducer housing, forming a first solidified layer;

adding subsequent layers of the powder above the first solidified layer and causing portions of the subsequent layers of the powder to solidify and bond to previously-formed solidified layers, forming subsequent solidified layers;

building the array of horns within a cavity while building the subsequent solidified layers; and

enclosing the cavity using the 3D printing technique.

11. The method of claim 10 wherein using a 3D printing technique comprises: leaving powder in the cavity between the horns unfused.

12. The method of claim 10 wherein the mini-horn array is round and is built onto the transducer housing concentric to the housing.

13. The method of claim 10 wherein using the 3D printing technique comprises and attaching the mini-horn array to the transducer housing comprise:

building the mini-horn array on the transducer housing;

wherein the method further comprises:

grasping the mini-horn array and

machining the transducer housing to be concentric with the mini-horn array.

14. The method of claim 9 wherein using the 3D printing technique and attaching the mini-horn array to the transducer housing comprise:

building the mini-horn array on a piece of stock material that is not built by the 3D printing technique and

machining the piece of stock material to form a portion of the transducer housing.

15. A transducer assembly for use in an ultrasonic flow meter, the ultrasonic transducer comprising:

a transducer housing comprising a first end, a second end, and a channel extending between the first and second ends, and a mini-horn array spaced apart from the channel and extending to the first end; and

a piezoelectric crystal disposed within the channel proximal the first end of transducer housing;

wherein the mini-horn array is built by a 3D printing technique, the array comprising:

an opening-free enclosure;

a plurality of horns disposed within the enclosure; and

powder disposed in the enclosure between the horns; and

wherein the opening-free enclosure is sealed by the 3D printing technique, retaining the powder inside the cavity.

16. The transducer assembly of claim 15 wherein the transducer housing comprises a front cap having a tubular cap body, and the channel extends into the cap body and

wherein the mini-horn array is formed directly on the cap body by the 3D printing technique.

17. The transducer assembly of claim 16 wherein the cap body is not fabricated by a 3D printing technique.

18. The transducer assembly of claim 15 wherein the enclosure includes a back plate, a front plate spaced apart from the back plate, and a wall extending from the back plate to the front plate and

wherein the back plate, the front plate, the wall, and horns are built by the same 3D printing technique.

19. The transducer assembly of claim 15 wherein the housing comprises a front cap extending from the first end, a tubular stalk sealingly engaging the front cap, a transducer retainer coupled to the stalk and extending to the second end;

wherein the front cap includes a tubular cap body formed from stock material that is not made by 3D printing;

wherein the channel extends into the tubular cap body; and

wherein the mini-horn array is formed directly on the tubular body by the 3D printing technique.