Power wrench for tightening screw joints
US5155421A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 5, 1991 |
| Grant date | Oct 13, 1992 |
| Priority date | — |
| Expiry date | Nov 5, 2011 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB25B21/008
- WIPO fieldMachine tools
- WIPO sectorMechanical engineering
Abstract
A power wrench for two-step tightening of screw joints, has a housing (13), an electric motor (10) including a rotor (25), an output shaft (24) coupled to the rotor (25), and a power supply. The power supply includes a power converter (11) with a variable frequency and voltage output and a current responsive power shut-off device. A retardation responsive inertia device (28) is coupled to the motor rotor (25) via a spring (32) and a cam (29, 30) for corotation with the motor rotor (25) and for activation of a switch (12) as a certain predetermined retardation magnitude in the motor rotor (25) is exceeded. The latter is used for obtaining a fast torque interruption of the initial tightening step of the two-step tightening process, whereas the final tightening step is discontinued automatically as a predetermined current magnitude in the power supply is reached.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.