US Patent 7370689 Thermo chromic heat storing/releasing device

A thermal chromic heat storing/releasing device includes a bag having an enclosed space for containing a heat storing/releasing material, and the heat storing/releasing material is a material that can store and release heat and the heat storing/releasing material is contained in the bag. A thermal chromic printed layer having at least a part disposed on the bag, and the printed material is mixed with a thermal chromic dye, such that the thermo chromic material will change the color of the printed layer for a visual indication as the temperature rises or drops.