METHOD OF MAKING AN ULTRASONIC SEARCH UNIT

• US 3,821,834 A
• Filed: 07/18/1972
• Issued: 07/02/1974
• Est. Priority Date: 07/18/1972
• Status: Expired due to Term

• Current Assignee: Staveley Instruments Incorporated
• Original Assignee: Jerry T. Mcelroy
• Inventors: McElroy, Jerry T.
• Primary Examiner(s): Lanham, Charles W.
• Assistant Examiner(s): Hall, Carl E.
• Application Number:
  US05/272,807
• Time in Patent Office: 714 Days
• Field of Search: 29/25.35 310/8.2,8.3 264/111,272
• US Class Current: 29/25.35
• CPC Class Codes: B06B 1/0681 and a damping structure
• CPC Class Codes: G10K 11/002 Devices for damping, suppressing, obstructing or conducting sound in acoustic devices G10K1/06 - G10K1/10 take precedence; for electro-mechanical transducers for communication H04R3/002
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

An ultrasonic nondestructive testing system and a search unit for use in such a system are disclosed herein. A method of manufacturing such a search unit is also disclosed. The search unit 10 includes a transducer crystal 36 for transmitting and receiving ultrasonic energy and a backing structure 60 behind the transducer crystal for dampening the crystal 36 against ringing and for attenuating any spurious ultrasonic energy radiated from the backside of the transducer crystal.

Claims

1. The method of making an ultrasonic search unit having a piezoelectric transducer crystal therein, including the steps of sealing a piezoelectric transducer in one end of a housing, forming a mixture of a powdered heavy metal and a low-foaming polyurethane resin, substantially filling the housing with said mixture, vibrating the housing with the mixture therein for a sufficient period of time to initiate a partial settling of the powdered metal in said mixture toward the transducer, and partially curing the resin at room temperature and below the foaming temperature until the resin is substantially solid, and fully curing the resin at an elevated temperature above the foaming temperature.

2. The method of claim 1 wherein said forming step includes combining one part resin with up to ten parts metal by weight.

3. The method of claim 2 including vibrating said housing with said mixture therein for an interval that is long enough to initiate a partial settling of the metal particles toward the transducer.

4. The method of making an ultrasonic search unit having a piezoelectric transducer crystal therein including the steps oF sealing a piezoelectric transducer in one end of a housing, at least partially filling said housing with a mixture of a polyurethane resin of the low-foaming variety and particles of a heavy metal, at least partially curing the resin at a temperature below the foaming point until the resin is substantially solid, and fully curing the resin at an elevated temperature above said foaming point until the resin is fully cured.

5. The method of claim 4 including combining said resin and metal particles in a ratio of up to ten parts metal to one part resin by weight.

6. The method of claim 5 including vibrating the housing with said mixture therein for an interval which will initiate a partial settling of the metal particles toward the transducer.