Polymeric security window
US4935723A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 21, 1989 |
| Grant date | Jun 19, 1990 |
| Priority date | — |
| Expiry date | Aug 21, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B13/1618
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A security window is a laminated pair of polymeric window panels having waveguides sandwiched therebetween for transmission of ultrasonic compression waves. The waveguide transmission medium is glass fibers extending from edge to edge of the plastic panels and distributed in plastic strips which cover the entire window area. The index of refraction of the glass fibers is as identical as possible to that of the surrounding plastics, making the waveguides substantially invisible. A transducer initiates an ultrasonic compression wave which travels the length of the waveguide, and is detected by a transducer at the other end of the waveguide. The received signal amplitude diminishes when the waveguide is damaged and such change is used to trigger an external alarm system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.