Inductive sensor with hermetically sealed connector

Abstract

1. Inductive sensor with a hermetically sealed connector. 2.1. State-of-the-art high-temperature-resistant and radiation-resistant inductive sensors require complex assembly. This promotes malfunctions due to the aging of sealing materials and can lead to failure. State-of-the-art connectors seal with additional sealing elements such as an O-ring. The new device minimizes malfunctions through hermetic sealing without the use of additional sealing materials, reduces installation effort to a minimum, and increases the sensor's service life. 2.2. The ball-and-cone connection between the connector element (1) and the mating connector housing (2) enables a hermetic seal without an additional sealing element and forms a detachable connector.The sensor is hermetically sealed by means of welded connections between the connection element (1), the measuring coil carrier (6), and the sensor housing (7). The signal-carrying pin contacts (4) are secured in the connection element (1) by means of a glass encapsulation (5) and hermetically sealed. Thus, the sensor is hermetically sealed in both the connected and disconnected states. 2.3. The inductive sensor is suitable for measuring linear displacements. An example would be the safety monitoring of the position of a pressure-reducing valve in a nuclear power plant within a containment structure under radioactive radiation and high temperature.

Description

The present invention relates to an inductive sensor having a measuring coil and a movable core according to the preamble of claim 1.PRIOR ARTInductive sensors serve for the detection and measurement of linear distances. For this purpose, a movable core is positioned within a measuring coil. Depending on the position of the core, a correlating voltage arises due to induction at the measuring coil, which is demodulated in a driver electronics and output as a position value.Patent CN00014184118A describes a highly temperature-resistant and radiation-resistant inductive sensor of the LVDT type. The materials thereof are selected such that the sensor can be exposed to high temperatures, radiations and pressures.The disadvantage of such a configuration of the sensor is that it is not hermetically sealed from the outside and the contacts for the measuring coil have to be expensively packaged. The internal life of the sensor or the connection contacts of the measuring coil are exposed to the environmental conditions in the worst case. For example, in the case of a suddenly arising high air humidity or superheated steam environment during a malfunction in the power plant, this can lead to the insulation resistance between the coil wires or the connecting lines decreasing and measurement inaccuracies thereby arising or the measurement system failing.Furthermore, each stranded wire must be individually fastened and sealed to terminals located in the sensor housing in order to pick up the electrical signal of the measuring coil. This entails a complicated and time-consuming installation on the part of the user. As a frequent consequence of incorrect processing, leaks arise which can lead to insulation loss and total failure of the measuring system during a fault with a superheated steam environment.Likewise included in the prior art are plug connectors which, as a stand-alone module, each consist of a male and a female plug element which are screwed together and sealed with an O-ring. Patent specification DE102014006874A1 discusses such an embodiment. These and many other connectors of similar construction are sealed with additional sealing elements. The disadvantage of conventional plug connectors already described, because of the use of additional sealing elements, of being susceptible to operating faults, is however not overcome here either.A sealing element as an additional component between two components to be sealed with respect to one another means an additional source of error and possibly a obligatory change of the sealing element due to wear and aging due to high temperature and radiation. This is very complicated if the sensor is installed in a power plant within a radiant environment of a containment, for example.OBJECT OF THE INVENTIONIt is an object of the present invention to provide a hermetically sealed, radiation- and highly temperature-resistant inductive sensor with a detachable self-sealing electrical connection without the use of additional sealing means.SOLUTION OF THE OBJECTTo achieve the object, the features of the listed claims lead.An inductive sensor according to the invention serves for detecting linear travel distances. It consists of a housing in which a measuring coil is arranged. A movable core is inductively coupled to this measuring coil. Depending on the position of the core, the induced voltage at the sensing coil changes. A hermetically sealed connection element serves as a connection possibility for a detachable mating connector in order to produce an electrical connection of the measuring coil to further components, in particular to driver electronics. This connection element is hermetically sealed to the sensor housing by means of a laser welding method, and the individual wires of the measuring coil are passed through pin contacts, which are hermetically sealed in glass, in the longitudinal direction. Furthermore, the hermetic seal in the transverse direction at the connection point of the connection element and the mating plug is ensured by a ball-and-cone connection.The connection element and the mating connector are detachably connected to one another. A union nut abuts the mating connector. This union nut has an internal thread matching the external thread which is located on the connection element. By tightening the union nut, the mating plug is pressed into the connection element and thus seals via the aforementioned ball-and-cone connection.At the end of the mating plug there is a likewise hermetically sealed corrugated protection tube. In this housing there are strands for the transmission of the electrical signals of the measuring coil.At the end of the corrugated protective tube there is a clamping box which is likewise hermetically sealing. In this housing there are terminals to which the strands coming from the measuring coil are connected. At the opposite side of these terminals, wires or cables are connected in turn, which conduct the electrical signals further to the driver electronics.The connection element and the union nut of the mating plug are designed with a hole pattern. This is part of a screw connection securing means between the connection element and the mating connector. After the union nut has been tightened with a certain torque, a plurality of securing wires are threaded through the bores of the hole pattern of the connection element and of the mating plug and both wire ends are twisted together.At least one or more cooling ribs are located on the connection element for lowering the temperature. Components within the connection element and the mating plug with corrugated hose are thus to be protected from high temperatures.All the described components of the measuring system, except for the driver electronics, consist purely of inorganic materials. This means that the measuring system is permanently radiation-resistant and is not subject to aging in radiation-loaded application areas. The aforementioned hermetic sealing of the sensor as a single system and the hermetic sealing of the remaining components between sensor and clamping box also prevent moisture from entering in the superheated steam environment and other media and thus ensure a long functionality. The inductive sensor is hermetically sealed in the plugged and unplugged state.FIELD OF APPLICATIONThe inductive sensor is suitable for measuring linear distances. An example would be the safety monitoring of the position of a pressure maintaining valve in a nuclear power plant within the containment under strong radioactive radiation and high temperature.DRAWINGSBrief Description of the DrawingsFIG. 1 shows the connection element and the mating connector of the inductive sensor according to the invention in a cut isometric view. FIG. 2 shows the entire measurement system without driver electronics in an isometric view. FIG. 3 shows a section through the entire measuring system from FIG. 2 in a side view with a detailed view Z. FIG. 4 shows a schematic diagram of the entire measurement system.DESCRIPTION OF THE EMBODIMENTFIG. 3 shows an inductive sensor according to the invention. This inductive sensor serves for the detection of linear travel distances. It has a housing H, consisting of a sensor housing 7 and a measurement coil carrier 6. A movable core 8 is inductively coupled to this measuring coil 9. This core is located in the axial direction of the measuring coil 9 in contactless fashion within the measuring coil carrier 6. A connection housing 1 is located adjacent to the housing H. The components "connection housing 1", "measuring coil carrier 6" and "sensor housing 7" are welded hermetically sealed axially or radially at their contact points to one another by means of a laser welding method. The connection housing 1 contains a plurality of bores in which a pin contact 4 is fastened in each case with the aid of a glass sprue 5. The interior of the laser-welded composite described up to now, consisting of "connection housing 1", "measurement coil carrier 6" and "outer sensor housing 7", is thus completely hermetically sealed. The pin contacts 4 mentioned are connected to the measuring coil 9 by means of a plurality of strands 12 in the interior of the sensor. A mating plug G, consisting of a mating plug housing 2, the mating plug contacts 14 and a union nut 3, can be connected to the connection housing 1. The mating connector housing 2 is welded to a corrugated protective tube 10, which is in turn hermetically sealed to a clamping box 11. The measuring coil 9 is electrically operatively connected to the terminal box 11 via the strands 12, the pin contacts 4, the mating plug contacts 14 and the strands 13. The terminal box 11 offers a connection possibility for strands to connect the driver electronics E (FIG. 4 ). There, the electrical signals of the measuring coil 9 are evaluated and the position of the core 8 in the measuring coil 9 is determined.FIG. 1 illustrates the re-detachable connection between the connection element S, consisting of the connection housing 1, the pin contacts 4 and the glass insert 5, and the mating plug G, consisting of the mating plug housing 2, the union nut 3 and the mating plug contacts 14. This enables simple and rapid connection and termination of the mating plug G and all components fastened thereto from the inductive sensor. For complete hermetic sealing, the remaining space between the connection element S and the mating connector G must also be hermetically sealed transversely to the longitudinal axis. This is achieved, as shown in the detail view Z in FIG. 3, by a ball-cone connection. The plug housing 1 is designed with an inwardly offset, round-running cone, while the mating plug housing 2 is designed with a spherical surface. By tightening the union nut 3, the spherical surface of the mating connector housing 2 is pressed into the cone of the connector housing 1. This results in a revolving tangential contact between the two components, as can be seen in detail view Z. In this form of the seal, the geometry of both components is elastically deformed in the region of the ball and the cone, respectively, and a contact surface is formed from the tangential contact line.In order to maintain the contact pressure between ball and cone permanently, the union nut 3 must be secured against independent release from external influences, such as vibration. This is achieved by using several fuse wires. These are threaded through a bore of the hole pattern P in the union nut 3 and a bore of the hole pattern P in the connection housing 1 and rotated together, so that there is no freedom of movement for the union nut 3 and an independent loosening is effectively prevented.The connection housing 1 is equipped with one or more cooling ribs C, as shown in FIG. 1. This advantageous embodiment reduces the heat transfer from the sensor housing in the direction of the pin contacts 4, since the sensor housing can be mounted directly on very hot heat sources and the highest temperatures are present there.The selection of materials for all components, except for the driver electronics E (FIG. 4 ), which is not exposed to radiation, is limited to inorganic materials. These are radiation-resistant and thus lead to a long lifetime and reliability of the measurement system.LIST OF REFERENCE CHARACTERS1 Connection housing 2 Mating plug housing 3 Union nut 4 Pin contact 5 Glass insert 6 Measuring coil carrier 7 Sensor housing 8 Core 9 Measuring coil 10 Corrugated protection tube 11 Clamping box 12 Stranded wires 13 Stranded wires 14 Mating plug contact H Housing consisting of 6 and 7 S Connection element consisting of 1, 4 and 5 G Mating plug consisting of 2, 3 and 14 E Driver electronics C Cooling ribs P Hole pattern T ThreadReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedCN 000114184118A

[0003] DE 102014006874A1

[0006]

Claims

Inductive sensor for detecting linear travel distances a) having a housing (H), b) a measuring coil (9), c) arranged in the housing (H), a movable core (8), d) inductively coupled to the measuring coil (9) and a connection element (S) for electrically connecting the measuring coil (9) to a mating connector (G), characterized in that the hermetic longitudinal sealing is carried out by a glass sprue (5) and the hermetic transverse sealing is carried out by a ball-cone connection.Inductive sensor according to Claim 1, characterized in that the connection element (S) and the mating connector (G) are detachably connected by a thread (T).Inductive sensor according to Claims 1 and 2, characterized in that the mating connector (G) is designed with a hermetically sealed corrugated protection tube (10).Inductive sensor according to Claim 3, characterized in that a hermetically sealing clamping box (11) is connected to the corrugated protection tube (10).Inductive sensor according to Claim 4, characterized in that the connection element (S) and the mating connector (G) are designed with a hole pattern (P) for screw connection securing.Inductive sensor according to Claim 1, characterized in that at least one or more cooling ribs (C) for lowering the temperature are mounted on the connection element (S).

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