Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1989-10-12
1990-12-11
Kaplan, G. L.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
G01N 2730
Patent
active
049768441
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a sensor construction particularly for the sealing and electrical insulation of ceramic or other fragile membranes in pressurized conditions where high temperatures prevail.
While using high pressures and high temperatures, the problem is the leading through of the sensors into these spaces so that they are not damaged under the influence of the fluctuation of pressure and temperature. For example in the measurements of pH and oxygen, the common practice is to use relatively fragile sensors, which may be easily broken under pressure when brought into a pressurized space.
The object of the present invention is to eliminate the above mentioned drawbacks. A particular object of the present invention is to introduce a sensor construction which also enables the use of fragile materials in sensors under high pressures.
As regards the characteristic novel features of the invention, the claims section is referred to.
The invention is based on the principal idea that the fragile sensor is placed in a pressurized space in an essentially freely movable position, to float in the insulating material so that an equally high pressure is effective on all sides of the fragile construction.
The sensor construction of the invention comprises a housing which forms the pressure balancing chamber and is essentially open towards the pressurized space; a hollow tubular sensor, open at the end nearest to the said chamber, partly located in this chamber and partly protruding out of it, the measuring chamber of the sensor being located at the outermost, closed end of the said sensor; and a conductor, which is lead into the chamber via a leadthrough arrangement known as such, and is connected to the sensor and insulated from the housing. Moreover, the space of the chamber surrounding the sensor is mainly filled with the insulating material, which is separated from the pressurized space by means of the advantageously annular piston provided around the sensor.
The sensor is advantageously a hollow rod-like ceramic or other fragile membrane open at one end and closed at the other, and a conductor is led into its outermost closed end, i.e. to the measuring chamber, via the open end. In between the measuring chamber and the open end of the sensor, there is a sealing chamber separated by means of screw units, which sealing chamber is filled with the insulating material while the screw units are freely movable under the influence of the pressure in the lengthwise direction of the sensor.
At the innermost end of the chamber, the part of the conductor which is located in between the screw unit and the leadthrough of the conductor, is bent to form a loose curve so that the sensor can be moved with respect to the housing without obstruction by the conductor. Advantageously the part of the chamber surrounding the sensor is provided with one or several guides, for instance sliding seal rings, which are arranged to be supported both by the sensor and the inner surface of the pressure balancing chamber so that they essentially prevent any transversal movements of the sensor, but allow the sensor to move freely in the lengthwise direction.
In the vicinity of the open end of the chamber, the piston sealing the space in between the chamber and the sensor can be a separate elastic ring, which is freely movable with respect to the walls of both the sensor and the chamber. It can also be an essential part of the sensor, for example made of the same ceramic material as the sensor, in which case the outer edge of this flange, resting against the chamber, is provided with sealing which prevents the insulating material from entering the other side of the piston. An essential feature for the insulating material, the piston and the guides is that they are all non-conducting so that the sensor is galvanically insulated from the housing.
The advantage of the invention, compared with the prior art, is that it enables the use of fragile sensors in high pressures and high temperatures, which has not been possible with the current me
REFERENCES:
patent: 2697070 (1954-12-01), Arthur
patent: 3145158 (1964-08-01), Matsuyama
patent: 3445366 (1969-05-01), Vermeer
patent: 4273637 (1981-06-01), MacDonald
patent: 4406766 (1983-09-01), MacDonald
patent: 4818366 (1989-04-01), Yonco et al.
Aaltonen Pertti
Illi Heikki
Selin Lauri
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