Marginal oscillator for acoustic monitoring of curing of plastics
US4758803A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 13, 1987 |
| Grant date | Jul 19, 1988 |
| Priority date | — |
| Expiry date | Jul 13, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2291/0251
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Changes in the ultrasonic properties of fiber-reinforced plastics during the curing process are monitored by a marginal oscillator to determine the degree of cure. The plastic sample and transmitting and receiving transducers serve as a narrowband acoustic resonator and are placed in the feedback loop of a variable gain amplifier; using gain control the system is allowed to marginally oscillate. The resonant frequency of the sample and amplifier gain are related to the velocity and attenuation of sound in the plastic and are determined by measuring the received signal frequency and amplifier gain control voltage. The system has frequency locking means to track changes in resonant frequency during the cure cycle.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.