Chain-type door latch and alarm
AssigneeChristoph Emmerich GmbH & Co. KG
InventorFranz J. Landkammer
Life of this patent
Estimating the term…
Abstract
A door latch and alarm apparatus has a support mounted on the door and a support mounted on the doorjamb. A relatively inextensible and flexible element is anchored to the door support and has a free end provided with an end piece fittable in a latch on the doorjamb support. A pair of conductors, one of which may be the inextensible and flexible element, extend from the door support to the end piece where they are connected together via a resistor. At their other ends these conductors are connected to a resistance detector which operates an alarm whenever the resistance between the two conductors increases, as when the conductors are broken, and whenever it decreases, as when they are short-circuited.
Claims13
A door latch and alarm apparatus comprising:
- a door-mounted support;
- a doorjamb-mounted support;
- a relatively inextensible and flexible element anchored to said door support and having a free end provided with an end piece receivable in said doorjamb support;
- latch means including key-operable mechanism on said doorjamb support for releasably securing said end piece thereto, whereby the door can open a limited distance from the doorjamb before said element becomes taut and impedes further opening;
- circuit means including a pair of conductors extending between said door support and said end piece and a relatively fragile connector in said end piece forming a closed conductive path with said conductors, said connector being so much weaker than said element that when same is stressed beyond a certain limit said connector interrupts said path before said element breaks;
- and
- alarm means on said door-support connectable to said conductors for emitting an alarm when said path is interrupted.
Dependencies are inferred from the claim text.