Protractor with an auxiliary ruler
US6457247B1 · kind B1 · utility
14Cited by
15References
5Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Jul 12, 2001 |
| Grant date | Oct 1, 2002 |
| Priority date | — |
| Expiry date | Jul 12, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B3/563
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A semi-circular protractor is provided at a center of circle with a through hole to which an auxiliary ruler having a length close to a diameter of the protractor is detachably and rotatably attached. With the auxiliary ruler, the protractor may be used to measure angles on a plane and on a three-dimensional body and to draw different angles. The protractor with the auxiliary ruler is designed for children to more easily understand the meaning of “angle” and to learn to use angles.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.