Interruptible time-temperature indicator

#What many industries need is a time-temperature indicator for learning what is going on in the field. For example, in the frozen food industry, a shipper would like to know if the shipments are being handled properly and if not, where they are being mishandled. To do this the shipper would need reliable time-temperature information available to him.

#One severe limitation of prior art time-temperature indicators such as those disclosed in U.S. Pat. No. 3,414,415 by Broad and U.S. Pat. No. 3,479,877 by Allen et al. is that they require on the spot trained observers to note, interpret and conclude what the indicator says. If the observer removes the indicator, it will continue to record change. If the observer forgets to read it promptly after removal, the information will probably be inaccurate. If the observer knows what the indicator should read, he can furnish the answers he thinks the shipper will like.

#It is an object of this invention to provide an indicator in which the time-temperature recordation can be stopped at any desired point in time, and which does not require an on the spot trained observer to interpret.

#Several embodiments of the apparatus of this invention are shown in the accompanying drawings in which like numerals denote like parts throughout the several views and in which:

#FIG. 1 is a top plan view of an embodiment of this invention wherein a wick with a weakened area (e.g. perforations) is employed;

#FIG. 2 is a top plan view of an embodiment of this invention wherein a wick with a weakened area (e.g. a notch) is employed;

#Additional objects, if not specifically pointed out herein, will be readily apparent to one skilled in the art from the following detailed description:

#The time-temperature indicator of this invention comprises a fluid source 10 and an interruptible wick 11. The fluid source can contain any one of the indicator substances known to prior art, or it can contain any substance which has a well-defined melting range and which has a set rate of migration along a wick when melted. For example, low molecular weight paraffins or eutectic solutions are useful, although factors such as storeability, desired melting range and migration rates must be considered in choosing the most suitable indicator substance. Preferably dyes are added to the indicator substances so the migration of the indicator substance on the wick will show up clearly. The fluid source is adapted to contain said indicator substance preferably through use of containers or porous pads.

#This fluid source is to be in contact with the interruptible wick upon activation of the indicator so as to allow migration of the indicator substance when melted on the wick. This activation can comprise of simply placing the wick in contact with the fluid source, or removing or rupturing a barrier placed in between the fluid source and the wick to prevent contact. The indicator substance can be either a liquid or a solid adapted to melt under conditions of use. The activation can also comprise means by which a liquid indicator substance contained in the fluid source upon freezing will expand and rupture the barrier between the fluid source and the interruptible wick thus allowing contact between the two. In summary, this activation can comprise of any means of placing the fluid source in contact with the interruptible wick so as to allow migration of the indicator substance contained in the fluid source onto the interruptible wick.