- 2014-12-01 (x)
- 1924-10-20 (x)
- Ko, Wen H. (x)
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Show moreBackground of the invention: This invention relates to a device for sensing pressure in industrial applications. More particularly, the invention is directed to a capacitive absolute pressure sensor having good stability, low power consumption, robust structure, large over pressure protection range, and good linearity and increased sensitivity when zero suppression is used. While the invention is particularly directed to the art of capacitive absolute pressure sensors, and will thus be described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications such as in accelerator and force sensors and diaphragm type actuators. The present invention preferably operates in the touch mode. Touch mode sensors have been disclosed, for example, in Ding et al., Touch Mode Silicon Capacitive Pressure Sensors, 1990 ASME Winter Annual Meeting, Nov. 25, 1990. Briefly, touch mode sensors can be described as follows. In capacitive pressure sensors using some type of diaphragm (whether or not in the touch mode) when a pressure is impressed upon the diaphragm, the diaphragm deflects. The deflection necessarily changes the gap below the diaphragm. The change in gap results in a capacitance change which is sensed and used to determine a measurement of the pressure. In the touch mode, the diaphragm is deflected to actually touch the surface therebeneath. The area that is touched is a factor in the magnitude of the change of capacitance. However, the disclosed sensors do not possess the useful characteristics of the present invention such as a vacuum sealed gap, or the connection to the area beneath the diaphragm using buried electrode structures to achieve electrical feedthrough for convenient sensing operations. Moreover, the disclosed sensors had stability and hysteresis problems which are overcome in the present invention. Additionally, U.S. Pat. No. 5,264,075 to Zanini-Fisher et al. discloses a fabrication method for silicon/glass capacitive absolute pressure sensors. The disclosed method of fabrication, however, is extremely complicated and results in a structurally distinct sensor. Generally speaking, conventional capacitive absolute pressure sensors operate in a limited temperature range of approximately -50.degree. to 100.degree. C. Further, no known sensors can withstand both specified operating temperature and pressure and much higher (many times the operating values) manufacturing temperature and pressure. For example, molding the sensor into a tire is but one illustration of an environment where conventional sensors fail to meet these desired criteria. Moreover, most known commercial devices of low and moderate costs have a base line drift problem with time in the field. Thus, the accuracy is typically worse than .+-.1% over approximately one year in the field, without calibration. The present design is able to overcome these industrial application problems. p
http://www.google.com/patents?vid=USPAT5528452
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Show moreBackground of the invention: This invention relates to a device for sensing pressure in industrial applications. More particularly, the invention is directed to a capacitive absolute pressure sensor having good stability, low power consumption, robust structure, large over pressure protection range, and good linearity and increased sensitivity when zero suppression is used. While the invention is particularly directed to the art of capacitive absolute pressure sensors, and will thus be described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications such as in accelerator and force sensors and diaphragm type actuators. The present invention preferably operates in the touch mode. Touch mode sensors have been disclosed, for example, in Ding et al., Touch Mode Silicon Capacitive Pressure Sensors, 1990 ASME Winter Annual Meeting, Nov. 25, 1990. Briefly, touch mode sensors can be described as follows. In, for example, capacitive pressure sensors using some type of diaphragm (whether or not in the touch mode) when a pressure is impressed upon the diaphragm, the diaphragm deflects. The deflection necessarily changes the gap below the diaphragm. The change in gap results in a capacitance change which is sensed and used to determine a measurement of the pressure. In the touch mode, the diaphragm is deflected to actually touch the surface therebeneath. The area that is touched is a factor in the magnitude of the change of capacitance. However, the disclosed sensors do not possess the useful characteristics of the present invention such as a vacuum sealed gap, or the connection to the area beneath the diaphragm using buried electrode structures to achieve electrical feedthrough for convenient sensing operations. Moreover, the disclosed sensors had stability and hysteresis problems which are overcome in the present invention.Additionally, U.S. Pat. No. 5,264,075 to Zanini-Fisher et al. discloses a fabrication method for silicon/glass capacitive absolute pressure sensors. The disclosed method of fabrication is extremely complicated and results in a structurally distinct sensor. Generally speaking, conventional capacitive absolute pressure sensors operate in a limited temperature range of approximately -50.degree. to 100.degree. C. Further, no known sensors can withstand both specified operating temperature and pressure and much higher (many times the operating values) manufacturing temperature and pressure. For example, molding the sensor into a tire is but one illustration of an environment where conventional sensors fail to meet these desired criteria. Moreover, most known commercial devices of low and moderate costs have a base line drift problem with time in the field. Thus, the accuracy is typically worse than .+-.1% over approximately one year in the field, without calibration. The present design is able to overcome these industrial application problems.
http://www.google.com/patents?vid=USPAT5585311
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Show moreField of invention: The present invention relates to respirator devices, and more particularly to an improved apparatus for delivering continuous positive airway pressure to a person (e.g., an infant) suffering from respiratory distress syndrome. Background of the invention: Idiopathic respiratory-distress syndrome has been reported to be the leading cause of respiratory failure in newborn infants. Infants afflicted with this syndrome experience substantial difficulty in breathing because the alveous of their lungs are unable to sustain inflation. In an effort to assist infants afflicted with idiopathic respiratory-distress syndrome, it has been proposed that continuous positive airway pressure be administered to such patients. See an article entitled "Treatment of the Idiopathic Respiratory-Distress Syndrome with Continuous Positive Airway Pressure" by Gregory et al., published in the June 17, 1971 issue of the New England Journal of Medicine (Volume 284, No. 24). While various types of continuous positive airway pressure administration apparatuses have been proposed and used (see, for example, U.S. Pat. Nos. 3,786,809; 3,827,433 and 3,842,828), none has proven to be entirely satisfactory. The prior art apparatuses for delivering continuous positive airway pressure to infants have been relatively complex in structure and design, have not been entirely reliable in use and/or require relatively expensive sterilization procedures following use by each patient. Another problem associated with the prior art apparatuses for administrating continuous positive airway pressure to patients is that such apparatuses have failed to provide means for minimizing rebreathing by the patient of exhaled or exhausted air. Objects and summary of the invention: In view of the foregoing, it is an object of the present invention to provide an improved apparatus for administering continuous positive airway pressure to patients, such as newborn infants suffering from idiopathic respiratory-distress syndrome, which is simpler and less expensive than the prior art apparatuses have been. It is a further object of the present invention to provide a continuous positive airway pressure administration apparatus which is sturdy, reliable and efficient in use. Another object of the present invention is to provide a simple, sturdy, reliable and efficient continuous positive airway pressure administration apparatus which is less expensive to manufacture than prior art apparatuses have been. Still another object of the present invention is the provision of a sterile apparatus for administering continuous positive airway pressure which does not require sterilization of the apparatus after each use. Another object of the present invention is the provision of a continuous positive airway pressure administration apparatus which is equipped with controls to assure that the air being delivered to the patient is at the proper, desired pressure.
http://www.google.com/patents?vid=USPAT4249527
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Show moreBackground of the invention: The present invention is in the field of diffused strain gauge pressure transducers. More particularly, the present invention relates to miniaturized pressure transducers capable of being implanted within the human or animal body for direct measurement of physiological pressures, such as respiratory, venous, arterial, amniotic, and cerebrospinal fluid pressures. Prior art transducers capable of monitoring physiological pressures in human beings and animals were normally not implanted in the body due to their undesirably large size, fragility, and complexity. These transducers were usually connected to the pressure source monitored by a fluid-filled catheter inserted into the body. This method of monitoring pressure often resulted in unreliable and inaccurate data, due to dynamic response problems associated with the fluid-filled catheter. Attempts to implant miniaturized pressure transducers within the body for direct measurement of internal fluid pressure often resulted in malfunctions due to leakage of body fluid into the critical components of the transducer. Summary of the invention: The present invention provides a miniaturized, fluid-tight pressure transducer capable of being implanted within a human or animal body. All components of the transducer are hermetically bonded together to provide a rugged, reliable sensor package. The transducer is assembled using known microcircuitry techniques, resulting in a finished pressure sensor measuring approximately 1.25 by 3.75 mm. with a depth of 0.250 mm. An N-type, phosphorus-doped, single crystal, silicon base and a single crystal silicon cover are eutectically bonded together by a metallic laminate seal in a vacuum environment to form an evacuated, fluidtight pressure reference chamber which contains piezoresistive bridge sensor elements diffused on a flexible diaphragm formed by preferential etching of the crystal silicon base of specific crystalline orientation. The diaphragm will flex or deform when there is a fluctuation of the pressure differential between the sealed pressure reference chamber and fluid external to the implanted pressure transducer. As the diaphragm flexes, the electrical parameters of the piezoresistive bridge will change proportionately. Electrical conductors lead from the piezoresistive bridge to a set of contacts external to the sealed reference chamber. These electrical conductors take the form of diffused, electrically insulated conductor paths on the surface of the silicon base where the conductors exit the evacuated chamber. Conventional electrical readout circuitry can be connected to the external transducer contacts to monitor and record fluid pressure, represented by the electrical parameters of the piezoresistive bridge. When utilized with an active temperature compensation circuit, the transducer can provide a linear output proportional to pressure that is stable to better than 1 mm. Hg at a 300 mm.
http://www.google.com/patents?vid=USPAT4023562
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Show moreDescription: 1. Field of the Invention: The invention relates to a surgically implantable device for measuring fluid pressure within a subject's skull or other body organs. 2. Background Articles: In hydrocephalic children, a birth defect causes excessive cerebro-spinal fluid to be generated in the brain. Excessive fluid pressure constricts the flow in blood vessels of the brain resulting in brain damage. Additionally, the brain under such pressure does not develop normally. Both of these conditions lead to mental retardation and, eventually, to death. A recently developed procedure to deal with this problem is to install what is known as a shunt. The shunt is a small conduit feeding from the brain area and "dumping" into the venous system, or into the stomach cavity. This relieves the pressure and sometimes prevents the tragic results. About 30% of the patients so treated will grow up to lead normal lives and sometimes the shunt can then be removed. Other problems result, however, if a shunt drains excessive fluid from the intracranial cavity. This causes the intracranial pressure to drop to an excessively low level. The brain is made up of various folds of tissue normally separated by pockets or cavities in between, called "ventricles". If insufficient fluid is present in the intracranial cavity, these ventricles will collapse. This also can result in brain damage and in severe headaches. It is therefore apparent that it is highly desirable to maintain the intracranial pressure within a rather narrow range. If intracranial pressure can be monitored on a frequent basis, there are ways of adjusting the pressure. Sometimes, the shunt can be provided with a valve which can adjust the flow of fluid from the intracranial cavity. In other instances, medical treatment by the use of drugs has been effective in adjusting pressure. Previously, pressure could be monitored only by an invasive technique. More specifically, a patch of the patient's hair is shaved off, and a needle is inserted through a small opening in the skull. A catheter attached to the needle delivers the fluid pressure to an external transducer which indicates intracranial pressure. The use of this invasive technique is limited in most patients to about once a month, and involves possible hazards of infection. Several attempts have been made to devise implantable telemetry devices which can more conveniently, safely, and frequently be used to monitor intracranial pressure. One of these devices is described in an article entitled "Intracranial Pressure Telemetry System" by KO et al Biotelemetry Patient Monitg. 8:131-150 (1981). This article also describes some of the history of the development of such apparatus and is incorporated here by reference.
http://www.google.com/patents?vid=USPAT4519401
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