Abstract: A device for monitoring temperature conditions in a frozen food storage space includes a rear panel and a parallel transparent plastic front wall having a peripheral skirt wall sealed to the panel front face. Laterally spaced projections intermediate the front wall top and bottom extend from the front toward the rear wall to delineate top and bottom cavity sections, one of which contains colored water. A suction cup is located on the panel rear face and indicia are formed on the panel front face registering with each cavity section. The device is located in the storage space until the water in the lower cavity section is frozen solid and is then inverted. The presence of water in the bottom cavity of the inverted device indicates the occurrence of a thawing condition in the storage space at the same time.

Abstract: An indicating device for indicating the time and temperature history of an object. The indicating device includes a reservoir containing an indicating material that liquefies at or above a predetermined temperature mounted on a base sheet, a removable barrier impervious to the indicating material interposed between the reservoir and a wick, wherein the wick is placed in contact with the reservoir after the barrier is removed to enable the migration of the indicating material along the wick at a controlled rate. The wick is constructed of generally hydrophobic materials so that the migration rate of the indicating materials along the wick is generally independent of changes in the ambient humidity.

Abstract: A container for a liquid crystal cumulative dosimeter including a resilient outer body sealed to confine a first liquid crystal composition constituent and a second liquid crystal composition constituent and having at least one transparent section to permit observation of the color of the confined composition, and a barrier contained completely within and physically unattached to the outer body for separating the first constituent from the second constituent, whereby disruption of the barrier allows the first constituent to mix with the second constituent. The barrier is formed either by encapsulating one or both of the constituents or by using air bubbles. Methods of manufacturing the various containers shown and processes of using those containers are also disclosed.

Abstract: A new and improved integrating indicator system operable to signal the attainment of one or more preselected time-temperature integrals which monitor the temperature and time history of a product utilizes a dual system of specific reaction pairs which simultaneously generate acid and alkali from two neutral substrates. One of the substrates is present in excess of the other. The preferred dynamic indicator system generates a constant pH buffer in the alkali range that is maintained until one of the substrates is depleted. At that time, a rapid pH change in the indicator solution to the acid range occurs, resulting in a very sharp visual color change in a pH-sensitive dye. In preferred embodiments, the specific reaction pairs are enzyme/substrate pairs, preferably urease/urea and yeast/triacetin.

Abstract: A low cost device which changes rapidly, significantly, irreversibly, and accurately when it is exposed to a predetermined temperature is disclosed. The device of the present invention employs a bimetallic disk which changes its configuration when it is exposed to a predetermined temperature. Before firing, the disk is captured by a recess in the device casing. When the disk is exposed to a predetermined temperature, it changes configuration and escapes its confinement from its orginal location in the recess. A spring propels the disk from its original location to a different location. Additionally, the spring ensures that the disk cannot return to its original location. This device has a minimal number of parts so that it is easily and inexpensively manufactured. It can be configured to sense either high temperature or low temperature. The low temperature device can be used in conjuction with irreversible temperature labels such that the combination records both a high and a low temperature exposure.

Abstract: A device for indicating whether a rise in temperature above a predetermined value has occurred includes a support member, such as a label, on which a temperature-sensitive material is deposited. The material includes a large number of fracturable microcapsules containing a medium which changes from a solid state to a liquid state at the predetermined temperature value. The viscosity of the medium in its liquid state and the material of the support member are chosen such that the distance d.sub.1 by which the medium flows across the support member after the fracturing of the microcapsules so as to activate the device is indicative of the time between activation of the device and cooling of the device to below the predetermined temperature value. If the temperature is subsequently allowed to rise above the predetermined value, the medium will again assume its liquid state and will flow further across the support member, reaching a distance of, say, d.sub.

Abstract: Described are cholesteric liquid crystal formulations suitable for use as indicators of time and/or temperature, and methods for reliably characterizing and reproducing initial and subsequent batches of such cholesteric liquid crystal formulations. The formulations have a time-dependent, temperature-dependent limit in a pseudo-irreversible liquid crystal phase wherein when said limit is exceeded, the formulations exhibit a color change which is irreversible by cooling.

Abstract: A temperature change indicator is described which is composed of an enzyme and a substrate for that enzyme suspended in a solid organic solvent or mixture of solvents as a support medium. The organic solvent or solvents are chosen so as to melt at a specific temperature or in a specific temperature range. When the temperature of the indicator is elevated above the chosen, or critical temperature, the solid organic solvent support will melt, and the enzymatic reaction will occur, producing a visually detectable product which is stable to further temperature variation.

Abstract: An elongated body of molded plastics material has an end portion with longitudinally spaced and laterally extending temperature numbers overlying corresponding bands of liquid crystal compositions, and an elongated lens of transparent plastics material covers the numbers and compositions and is sealed to the end portion of the body around the compositions. In one embodiment, the compositions are carried by an aluminum strip or foil which has a center portion spaced within a cavity and opposite edge portions projecting to the outer surface of the body between the lens and the body end portion. In another embodiment, the body end portion has longitudinaly spaced cells or cavities for receiving the liquid crystal compositions in a slurry form, and in a further embodiment, the body is molded of a transparent plastics material and has an end portion which forms a second lens to provide a double-sided thermometer.

Abstract: This invention relates to a temperature control indicator unit comprising a substrate having supported thereon (a) microcapsules enclosing a hydrophobic organic compound possessing an arbitrarily selected melting point, (b) a methine dye and (c) an oxidizing material. More particularly, a unit made by combining an irreversibly color-developing methine dye and an oxidizing material with microcapsules enclosing a hydrophobic organic compound possessing a predetermined melting point and supporting them on a substrate is used for temperature control purposes. A suitable measure is taken, preferably at or below the desired control temperature, to break at least a part of the microcapsules of the unit and thereby produce fissures or the like in the microcapsule membrane. Then, the unit is stored or transported together with an article to be placed under temperature control.

Abstract: A disposable maximum reading thermometer comprises a body (40) in which a capillary passage is defined, a reservoir (41) communicating with the passage and a heat expansible indicator medium (46) contained in the reservoir. The reservoir and the passage are adapted to allow expansion of the medium in the passage when the medium is subjected to heating. At least a part of the passage wall exposable to the indicator medium is adapted to undergo a detectable and irreversible change of its light penetration characteristics when brought into contact with the medium. The capillary passage is defined by a rod (48) arranged in a longitudinally extending bore (42) of the body (40). The surface of the rod is frosted (matt) or opalized, preferably by a mechanical treatment, and adapted to be deopalized when brought into contact with the medium.

Abstract: The present invention provides a temperature-indicating sheet which, when exposed to temperatures higher than the prescribed temperature in temperature-control for the common low-temperature preserved goods, changes in color according to the exposure temperature and time. This object is attained by arranging one component which melts at the prescribed temperature and a substance which irreversibly changes in color in contact with said component through a membrane permeable to the component. The sheet of the present invention comprises a component which melts at the prescribed temperature, a substance which changes in color in contact with the component and a membrane permeable to the molten component, said component being included in microcapsules which can be broken by outer pressure at a temperature used, and in which the component and the substance are arranged at the opposite sides with respect to the membrane.

Abstract: System and means for irreversibly recording the incidence of a predetermined temperature comprising a cholesteric liquid crystal system and an activator material capable of interacting with the liquid crystal system to induce a unique irreversible change in the optical properties thereof sustantially at the predetermined temperature. The system preferably includes means for separating the liquid crystal system and activator at temperatures below the activation temperature of the activator.

Abstract: A recording device is described, useful as an integrated time-temperature or radiation-dosage history indicator. The device contains a substrate having deposited thereon at least two indicating units, one being unreacted and representing zero time of exposure and the other unit being pre-reacted. Each unit is comprised of an acetylenic compound containing at least one --C.tbd.C--C.tbd.C-- group, capable of reacting by 1,4-addition polymerization thereby forming an end-point color after an irreversible, progressive color change upon thermal annealing or exposure to actinic radiation. The end-point color represents an integrated time-temperature history of thermal annealing or radiation-dosage history. Each unit is constructed such that the time required to form the end-point color by thermal annealing at a given temperature or for a known thermal history, or exposure to actinic radiation at a given average radiation dosage rate, is predetermined.

Abstract: Temperature profiles at elevated temperature conditions are monitored by use of an elongated device having two conductors spaced by the minimum distance required to normally maintain an open circuit between them. The melting point of one conductor is selected at the elevated temperature being detected, while the melting point of the other is higher. As the preselected temperature is reached, liquid metal will flow between the conductors, creating short circuits which are detectable as to location.

Abstract: A temperature measuring device for very high design temperatures (to 2,000.degree. C.). The device comprises a homogenous base structure preferably in the form of a sphere or cylinder. The base structure contains a large number of individual walled cells. The base structure has a decreasing coefficient of elasticity within the temperature range being monitored. A predetermined quantity of inert gas is confined within each cell. The cells are dimensionally stable at the normal working temperature of the device. Increases in gaseous pressure within the cells will permanently deform the cell walls at temperatures within the high temperature range to be measured. Such deformation can be correlated to temperature by calibrating similarly constructed devices under known time and temperature conditions.

Abstract: Novel and stable compositions of matter are disclosed which change color sharply upon a transition from a liquid state to a solid state or from a solid state to a liquid state, which change of state is at substantially a predetermined temperature corresponding to a temperature to be measured.The constituents of the novel compositions of matter comprise:1. a solvent (I) consisting of a single substance or a mixture of substances and adapted to change from a solid state at substantially a predetermined temperature to a liquid state and2. an indicator system (II) consisting of one or more substances different from (I), characterized in that(a) (II) is soluble in (I) when the latter is in the liquid phase, and(b) (II) changes color visible to the naked eye when (I) passes from the solid to the liquid phase or from the liquid to the solid phase.Thermometers containing said stable compositions of matter are also disclosed.

Abstract: A device for monitoring thermal energy input and displaying the relationship of the thermal energy input to a selected time/temperature relationship. The device employs an indicating material which, when melted, expands and flows into a narrow channel to provide an irreversible, visible indication of the thermal energy to which the device has been exposed.

Abstract: A new and useful all plastic disposable thermometer is disclosed, which dispenses with the prior art employment of an aluminum or other metal-based substrate. The novel thermometer can either be employed with opaque indicator means or with heat-sensitive compositions of matter that change color with a change in phase, such as those enumerated in copending application Ser. No. 946,935, filed Sept. 28, 1978, now U.S. Pat. No. 4,232,552.

Abstract: Tamper proof apparatus for verification that a critical temperature has been reached or exceeded includes a permanently sealed casing and cap containing a thermal element connected to a rotatable cam having a temperature indicator extending outwardly therefrom adapted to rest under a transparent window in the cap when critical temperature has been reached. Maximum and minimum temperature stops on the cap prevent movement of the indicator beyond preselected positions. An opening through the cap engages a removable shipping pin cooperating with either the maximum or minimum temperature stop to prevent movement of the indicator during shipment or storage. A locking spring connected to the cap traverses the lateral surface of the cam until the spring engages a shoulder formed in the cam. The shoulder and spring have, respectively, a first spur and a second spur that engage in permanently locked position when a critical temperature has been reached.

Abstract: An aging gauge comprising a container having a fixed or a variable sized t opening with a cap which can be opened to control the sublimation rate of a thermally sublimational material contained within the container. In use, the aging gauge is stored with an item to determine total heat the item is subjected to and also the maximum temperature to which the item has been exposed. The aging gauge container contains a thermally sublimational material such as naphthalene or similar material which has a low sublimation rate over the temperature range from about 70.degree. F. to about 160.degree. F. The aging products determined by analyses of a like item aged along with the aging gauge for which the sublimation amount is determined is employed to establish a calibration curve for future aging evaluation. The aging gauge is provided with a means for determining the maximum temperature exposure (i.e., a thermally indicating material which gives an irreversible color change, Thermocolor pigment).