Abstract: A pop-up thermometer having an elongate housing formed with a longitudinally extending bore, a plurality of internal neck regions, and a plurality of internal cavities. The neck regions each having a minimum diameter portion and a neck locking surface extending outwardly from the minimum diameter portion of the neck. An indicator rod slidably disposed in the bore of the housing includes at least one stem stretch having a diameter less than the remainder of the bore and a stem locking surface extending outwardly from said stem stretch. A fusible material fills the internal cavities. When the fusible material is in solid form, the neck locking surface exerts a substantially downward directed force on said stem locking surface on the rod to resist upward movement of the rod relative to the housing.

Abstract: A pop-up thermometer having an elongate housing formed with a longitudinally extending bore, first and second internal neck regions, a first internal cavity and a second internal cavity. An indicator rod slidably disposed in the cavity includes a front end portion, a first stem stretch extending from the front end portion and terminating in a raised portion, a second stem stretch extending from the raised portion and a rear end portion spaced from the front end portion. The front end portion and the first stem stretch are positioned in the first internal cavity while the second stem stretch is positioned in the second internal cavity. The first stem stretch has a lesser cross sectional diameter than the front end portion of the rod. A fusible material substantially fills the first internal cavity, engaging the front end portion and at least a portion of the first stem stretch to retain the indicator rod in the housing.