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Case Western Reserve University Patents
Show moreBackground of the invention: 1. Field of the Invention: This invention relates to a strain gauge having alternate sections of concave and convex, concave and flat or square wave shapes that can be stretched with very little force and to a method of making such a strain gauge. 2. Description of the Prior Articles: Heretofore, most strain gauges were of the type adapted to be bonded to a substrate to provide a measurement of strain of an object. In the measurement of dynamic movement, such as abdominal movement of an infant to monitor respiration, such a strain gauge would be unsatisfactory in that it would restrict movement and interfere with the breathing process. One strain gauge which has been used for this purpose in the past, is the mercury strain gauge. This comprises a flexible thin wall rubber tube filled with a conductive medium such as mercury and having electrical contacts at opposite ends. As the tube is stretched, the body of mercury becomes longer and thinner and the resistance through the gauge is increased. This type of gauge, in this application, has several drawbacks. First, as oxygen diffuses through the rubber tube, the mercury can oxidize and provide intermittent electrical contact. Also, because of the toxic nature of mercury, use of the gauge is limited to a carefully watched clinical setting and can not be used at home. Other home use infant respiratory monitors are subject to false readings and at times can be unreliable. Summary of the invention: The strain gauge of the present invention includes an elongated base of polyester or similar material which may be easily flexed and has alternating concave and convex sections, such as corrugations, extending widthwise of the base. Strain gauge sections of high resistance are provided on the concave sections of the base subject to tension when the base is elongated while low resistance connections or nodes are provided on the convex sections. A principal object of the present invention is to provide a novel strain gauge which has very little resistance to stretching, does not have to be bonded to a substrate for its full length and which will not interfere with or restrict movement of the object being tested or monitored. Another object of the present invention is to provide a novel strain gauge designed to detect dynamic movement of a body rather than measure strain and not interfere with such dynamic movement. Yet another object of the present invention is to provide a strain gauge that will convert large elongations into small surface strains within the range of the strain gauge. A further object of the present invention is to provide a novel infant respiration and apnea sensor which can be taped or otherwise secured at its opposite ends to an infant's abdomen or thorax and detect movement due to breathing without impairing the infant's breathing effort and also detect episodes of apnea.
http://www.google.com/patents?vid=USPAT5079535
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