Invented by David Ernest Havens, Patrick J. Hood, Teresa E. Havens, Joel J. Everhart, Aaron M. Schneider, Cornerstone Research Group Inc
The Cornerstone Research Group Inc invention works as followsThe present invention uses the unique shape recovery characteristics of shape memory materials and shape memory polymers to provide a cheap and easily identifiable method to determine when a product is exposed to environmental conditions which would likely make it appear that the product is expired or unfit for usage. The shape memory material can be attached to an indicator device and allowed to change its shape when exposed to environmental conditions.
Background for Environmental Condition Cumulative Tracking Integration Sensor using Shape Memory Polymer
The present invention is a method and apparatus that detects environmental conditions surrounding perishable goods and displays this information visually in an easy to read format. Environmental conditions can affect the suitability of the product for use, or its spoilage. These embodiments are useful for determining the suitability of products with long shelf lives, such as ammunition and fuel. They can also be used to determine the likelihood of spoilage of products that have a short shelf life, such as frozen meats and vegetables.
The monitoring and controlling of environmental conditions can enhance the shelf life of products, but cannot give them an indefinite shelf life. By controlling environmental conditions that decrease the chances of products becoming defective over time. In particular, recent health concerns about spoiled food led to several governments requiring or suggesting that all food requiring cooling for transportation or storage must be constantly monitored to minimize the chance of spoilage from exposure to higher temperatures.
One of the risks of food transportation is the risk of growth of bacteria like Clostridium Botulinum, which produces botulinum toxin in food. In the past, consumers could tell by smell, appearance and texture if a food was likely to spoil. The bacteria that can cause food poisoning are not the main reason for changes in smell, appearance and feel. They are caused by oxygen or ultraviolet light. Modern packaging and refrigeration means that most foods do not receive enough oxygen or ultraviolet light for them to be spoiled by traditional methods.
Since most bacteria will grow on food without oxygen, it is important to keep the temperature of the food below a certain level. This would be between 32-33 Fahrenheit, or 0 to 0.55 degrees Celsius. Over a few weeks, a temperature increase of just 34 or 36 degrees, or 0.5-2 degrees Celsius can cause C. Botulinum to multiply in enough numbers to cause food-poisoning. The present invention is able to determine when food has become spoiled by continuously monitoring the temperature of the environment around the food.
The temperature is not the only factor that affects the usefulness and quality of products. Relative humidity, or the pressure of water vapor in the air around the product can expose it to excessive amounts of water, which can degrade some products, including but not restricted to potato chips and crackers, as well as bread, pastas, vegetables, meats and other foods.
The present invention allows for the monitoring of humidity and temperature in the surrounding environment of a product. This can affect both the shelf life and usefulness of other products, such as ammunition and fuel. Ammunition has a typical shelf life of at least 20 years. This shelf-life is affected by excessive humidity and temperature. The present invention allows for a quick, visual indication as to whether ammunition has been stored for a long time.
Prolonged exposure of high humidity and heat accelerates aging and reduces service life for many products. This is true both for military and commercial products. It is impossible to track environmental exposures for products with long lifespans. The tracking of ordinance is a challenge because it can be stored on land and at sea for years, or loaded in different environments. As ordinance is transported, mixed, and transferred, it’s relative freshness cannot be determined. In fact, the age of the stock plays only a small role in its overall freshness. The use of sensing devices will allow ammunition/ordinance that is freshest to be saved for critical situations.
The present invention provides a way to track the relative suitability for use of a variety of classes of goods without using any electronic means. However, it should be obvious to those in the know that electronic means can also be incorporated in the present invention to be used in an inventory tracking systems as described below.
2. Background Art
A temperature-sensitive product will not spoil or decay as a direct result of being exposed to a certain temperature. The product spoils because of the heat it receives as a result a temperature change over time. “The present invention differs from the prior art in that it uses shape memory materials, specifically shape memory plastics, to track cumulatively a product’s exposure to different environmental conditions over time. It can do this cheaply, accurately and without any electrical devices.
Shape Memory Polymers were first introduced in the United States of America in 1984. “Shape Memory Polymers (hereinafter?SMPs? properties. SMPs, or shape-memory polymers, are polymers whose name is derived from their ability to return back to their original “memorized” shape after undergoing a shape deformation. A Journal of Food Protection article (Vol. 61. No. 9. 1998. Pages 1154-1160), entitled “Conservative Predictions of Time for Clostridium Botulinum toxin Formation to be Used with Time-Temperature Indices to Ensure Food Safety” Guy Skinner, John Larkin and others have outlined the need for sensor technologies such as those CRG is developing. This paper describes a market for CRG?s technology. This market is also known as the Larkin Market.
In summary, Larkin’s market includes foods packaged in various forms of reduced-oxygen packaging (hereafter referred to as?ROP”). ROP creates a sterile environment which reduces the growth rate of anaerobic organisms. It allows fresh foods to have a longer shelf-life and expands the range of fresh foods, such as seafood. In this market, foods that aren’t frozen are considered fresh foods. Fresh foods are considered premium, and consumers will pay a premium for them. Therefore, the margins of this fresh food segment in the consumer food industry are higher.
The chain is liable for the quality because the food, such as seafood, may be repackaged and packaged several times from the dock to the supermarket. Each link in the chain assumes responsibility for the overall chain. The present invention reduces consumer-related death rates, reducing insurance costs and increasing profits for businesses.
All SMPs are at least one temperature of transition (hereinafter Tg?) The SMP changes from a rigid, hard plastic to a flexible, soft elastomeric material at this temperature. The SMP is soft when it is above Tg, and hard below Tg. The SMP can be generally deformed once the temperature is above the Tg. To ‘lock’ in the deformation, the SMP must be cooled down below its Tg and maintained in the desired shape. The deformation must be?locked in’ by cooling the SMP below its Tg while maintaining the desired shape. The polymer network will not return to the original shape or’memorized’ shape once the deformation has been locked. Thermal barriers prevent the polymer network from returning to its original or?memorized? shape. The SMP will retain its deformed form indefinitely, until it is heated again above its Tg. At this point the mechanical strain stored by the SMP is released and it returns to its “memorized” shape. shape. The Tg is the average temperature where a material changes from a rigid to an elastic polymer. It is important to note that the Tg represents the average temperature at which a material transitions from a rigid polymer into an elastomeric polymer. This limited recovery is usually small and close enough to Tg so that it doesn’t affect the function of the SMP.
The SMP material can be heated to above its Tg and still retain the flexibility of an elastomer. It can also be quickly reshaped to the memorized form, then cooled to a rigid plastic. This change can be repeated many times without affecting the material.
The SMP transition is not a thermally induced phase change, like with shape memory alloys. SMPs also have a much wider range of flexibility and capability than SMAs in terms of shape configuration and manipulation.
There are three types: thermoplastics (thermally activated), thermoplastics (partially cured resins) and thermosets (fully cured thermosets). The first two types of thermally activated SMP have limitations and drawbacks. The properties of partially cured resins change with each cycle. Thermoplastic thermoplastic SMP “creeps” Thermoplastic SMP ‘creeps,? It gradually ‘forgets’ its memory shape with time. “A thorough understanding of chemical mechanisms will allow those skilled in the art to customize the formulation of SMP to specific needs.
Polymers of various types have shape memory properties. Polyurethane polymers are probably the most researched and well-known polymer type that exhibits shape memory polymer characteristics. Gordon, Proc of First Intl. Conf. Shape Memory and Superelastic Tech. 115-120 (1996) and Tobushi and al., Proceedings of First Intl. Conf. Shape Memory and Superelastic Tech. 109-114 (1994) are studies that focus on the properties and applications of shape memory polyurethanes. S. Ota reported on a polymeric system based upon crosslinking homopolymer polyethylene. Phys. Chem. 18, 81 (1981). Japan Kokai JP 63-179955 also claimed that a styrene/butadiene copolymer system exhibited shape memory properties. Japan Kokai JP 62-19440 also claimed that polyisoprene exhibited shape memory properties. Kagami, et. al., Macromol, revealed another polymeric system. Rapid Communication, 17, 539-543, (1996) is a class of copolymers containing stearyl acrylicate, acrylic acid, or methylacrylate. Other SMP polymers known in the art includes articles formed of norbornene or dimethaneoctahydronaphthalene homopolymers or copolymers, set forth in U.S. Pat. No. 4,831,094.Click here to view the patent on Google Patents.