Safety device for an electric power tool
US4739435A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 24, 1986 |
| Grant date | Apr 19, 1988 |
| Priority date | — |
| Expiry date | Jan 24, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H7/093
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A safety device for an electric power tool, especially a portable tool. It has a main switch, electronic controls, a tachometer-generator, and a relay. The relay electrically parallels the motor, acts on the supply of current to the motor through a relay contact, and is activated through the tachometer-generator and through a subsequent safety circuit. To provide a means of switching off the motor at excessively high speeds that will be inexpensive to manufacture and that will maintain a constant switch-off reference speed throughout its life, the safety circuit consists of a synchronization stage, an adjustable timer stage, a processing stage, an ignition amplifier, and an output section.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.