Equatorial sundial with simple time and date interpretation
US6871407B1 · kind B1 · utility
Inventor
Key dates
| Filing date | Sep 18, 2003 |
| Grant date | Mar 29, 2005 |
| Priority date | — |
| Expiry date | Sep 18, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG04B49/02
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
This invention represents an improvement to an equatorial sundial comprising an independent simultaneous single scale indication of both time and date as represented from a primary and secondary gnomon. This allows one unfamiliar with the physics of an equatorial sundial to with simple observation quickly assess both time and date as a singular measurement. The sundial displays conventional time measurement on a single scale transcribed on the equatorial ring from a primary gnomon aligned with the polar axis. The improvement includes a date scale transcribed on the primary gnomon that is cast a shadow from the secondary gnomon comprised of the upper equatorial ring. Since the sun maintains an essentially equivalent angle of declination throughout the day, the shadow cast by the upper equatorial ring (secondary gnomon) on the primary gnomon (containing the date scale) remains consistent in position and date can be observed at any time of the solar day.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.