Frangible construction lock system
US3998080A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 30, 1975 |
| Grant date | Dec 21, 1976 |
| Priority date | — |
| Expiry date | Apr 30, 1995 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T70/774
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A pin tumbler lock has a housing, a cylindrical key plug provided with a keyway rotatable in the housing, a shear line between the plug and the housing, pin tumbler bores with aligned parts respectively in the housing and the key plug and spring pressed outer and inner pin tumblers in each bore. In one of the bores is an extra frangible graphite tumbler of substantially the diameter of the other pin tumblers. When construction key is inserted in the keyway the graphite tumbler and the other pin tumblers meets at the shear line permitting the lock to unlock. When construction is finished a conversion key is inserted in the keyway and the graphite tumbler is shifted to a position crossing the shear line whereupon the graphite tumbler is shattered by rotation of the key plug. Thereafter the lock can not be unlocked by the construction key but can be unlocked by the householder's key.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.