Indicator for display of elapsed times and/or of the moment when changes of state occur

US5317987A · kind A · utility

Assignee

• Badische Tabakmanufaktur Roth-Handle GmbH · DE

Inventors

• Hubert Muller · Grevenbroich, DE
• Bruno Langenfeld · Waldkirch, DE

Key dates

• Filing date: May 4, 1992
• Grant date: Jun 7, 1994
• Expiry date: May 4, 2012

Classification

• Technology area (CPC G): Physics
• CPC primary: G07C1/00
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An indicator for attachment to objects to display elapsed times and/or changes of state, in which a visible display is brought about by color change of the indicator upon reaction of chemical substances and with destruction of a barrier preliminarily separating the chemical substances. The barrier is a separating or covering layer that can be penetrated by selective pitting by a chemical substance preliminarily enclosed by the barrier. An embodiment of the invention includes selective pitting of the barrier member with a resulting visible change of the indicator. Another embodiment of the invention includes initial separation of two chemical substances that can react with one another with visible change, of which at least one reacts chemically with the barrier for the latter's penetration.