Inductive sensor with hermetically sealed connector

Abstract

Inductive sensor for measuring linear distances with a) a housing (H), b) a measuring coil (9) arranged in the housing (H), c) a movable core (8) inductively coupled to the measuring coil (9), d) a mating plug (G) e) and a connecting element (S) for electrically connecting the measuring coil (9) to the mating connector (G), characterized in that a hermetic longitudinal seal of the inductive sensor is provided by a glass encapsulation (5) of pin contacts (4) of the connecting element (S) and a hermetic transverse seal of the inductive sensor is provided by a ball-cone connection, wherein the connecting element (S) and the mating connector (G) are detachably connected by a thread (T), and the connecting element (S) and the mating connector (G) are each provided with a hole pattern (P) for screw locking.

Description

[0001] The present invention relates to an inductive sensor with a measuring coil and a movable core according to the preamble of claim 1. The further claims describe advantageous embodiments of the invention. STATE OF THE ART

[0002] Inductive sensors are used to detect and measure linear displacements. A movable core is positioned within a measuring coil. Depending on the core's position, an induction voltage is generated across the measuring coil, which is demodulated by driver electronics and output as a position value.

[0003] As an example of a printed prior art document, CN000114184118A can be mentioned, which describes a highly temperature-resistant and radiation-resistant inductive sensor of the LVDT type. Its materials are selected so that the sensor can withstand high temperatures, radiation, and pressures.

[0004] The disadvantage of this type of sensor design is that it is not hermetically sealed from the outside, and the contacts for the measuring coil require complex assembly. In the worst-case scenario, the sensor's internal components or the measuring coil's connection contacts are exposed to environmental conditions. For example, a sudden increase in humidity or a hot steam environment during a power plant malfunction can cause the insulation resistance between the coil wires or the connecting leads to a decrease, resulting in measurement inaccuracies or system failure.

[0005] Furthermore, each wire used to tap the electrical signal from the measuring coil must be individually attached to terminals located inside the sensor housing and sealed. This results in a complex and time-consuming installation for the user. A frequent consequence of faulty workmanship is leakage, which can lead to insulation loss and total failure of the measuring system during a malfunction in a hot steam environment.

[0006] Connectors that function as self-contained modules, each consisting of a male and a female connector element, are screwed together and sealed with an O-ring. German patent DE102014006874A1 describes such a design. These and many other connectors with a similar construction are sealed with additional sealing elements. However, the previously described disadvantage of conventional connectors—their susceptibility to malfunctions due to the use of these additional sealing elements—remains unresolved.

[0007] An additional sealing element between two components requiring sealing introduces an additional potential point of failure and may necessitate replacement of the sealing element due to wear and aging caused by high temperatures and radiation. This is particularly costly if the sensor is installed in a power plant within a radioactive environment, such as a containment structure.

[0008] Furthermore, reference is made to DE 2914195C2, which also describes an inductive sensor according to the preamble of claim 1 with a connecting element for electrically connecting the measuring coil to a mating connector, in which the coil assembly is embedded in an injection-moldable, centrifugally molded, or castable plastic for sealing purposes. Plastics are not suitable for continuous use under radioactive radiation or at high temperatures, as their organic structure makes them subject to physical aging and there is a risk of failure. Furthermore, the connecting element lacks an effective means of hermetically sealing the mating connector. The known transmitter cannot be used for operation under radioactive radiation or at high temperatures.

[0009] CN 203445325U describes a connector with a terminal element and a mating connector, wherein the hermetic longitudinal seal is achieved by a glass encapsulation and the hermetic transverse seal by a ball-and-cone connection. However, this known connector does not solve the problem of the invention, since the mating connector consists of three individual parts, and the hermetic longitudinal seal is only achieved by screwing the mating connector to the terminal element. If an inductive sensor were equipped with this connector, the hermetic longitudinal seal would not be achieved without the screwed-on mating connector, and moisture could penetrate the inductive sensor, causing malfunctions or even destroying it. The object of the present invention, however, is to produce a hermetically sealed inductive sensor with a detachable connection.

[0010] Furthermore, DE 19906800A1 describes a pressure medium reservoir with an inductive sensor and a movable core, which is hermetically sealed by a media separation element. The present invention, however, describes an inductive sensor without the use of additional sealing agents. Furthermore, the movable core is located within the media separation element and can only be displaced by a change in pressure. Its use is therefore limited to applications that involve a pressure change.

[0011] A similar known invention is shown in DE 10018189A1, which also uses a media separation element as an additional sealing agent. This invention also does not solve the problem of the present invention.

[0012] DD 235138A1 and CN 113193420A describe a connector using two corresponding sealing surfaces which, through appropriate contact pressure, create a hermetic transverse seal to the surrounding medium. However, if the connector is disconnected, the internal components of the sensor or the connection contacts of the measuring coil would, in the worst case, be exposed to the environmental conditions. This could lead to a decrease in the insulation resistance between the coil wires or the connecting leads, rendering the inductive sensor unusable. Due to the lack of a hermetic longitudinal seal, this connector also fails to achieve the objective of the present invention.

[0013] US 2015 / 0369406A1 and US 2019 / 0334339A1 describe a push-fit connector comprising a corrugated hose and an additional seal attached to one end of the hose, forming a detachable connection element. This connector, and many others of a similar design, are sealed with additional sealing elements. However, the previously described disadvantage of conventional push-fit connectors—their susceptibility to malfunctions due to the use of these additional sealing elements—remains unchanged.

[0014] In KR 202009006393U and JP H08-339864A, a connector element with cooling fins is shown to reduce the temperature of the connector. However, both documents only describe a general plug connector that is designed with cooling fins. TASK OF INVENTION

[0015] The object of the present invention is to provide a hermetically sealed, radiation- and high-temperature-resistant inductive sensor with a detachable self-sealing electrical connection without the use of additional sealing agents. SOLUTION TO THE TASK

[0016] The features of the listed claims lead to the solution of the problem.

[0017] An inductive sensor according to the invention serves to detect linear displacements. It consists of a housing in which a measuring coil is arranged. A movable core is inductively coupled to this measuring coil. The induced voltage at the measuring coil changes depending on the position of the core. A hermetically sealed connection element serves as a connection point for a detachable mating connector to establish an electrical connection between the measuring coil and other components, in particular with driver electronics. This connection element is hermetically sealed to the sensor housing by means of a laser welding process, and the individual wires of the measuring coil are routed longitudinally via pin contacts hermetically sealed in glass. Furthermore, the hermetic seal in the transverse direction at the connection point of the connection element and the mating connector is ensured by a ball-and-cone connection.

[0018] The connector and mating plug are detachably connected. A union nut rests against the mating plug. This union nut has an internal thread that matches the external thread on the connector. Tightening the union nut presses the mating plug into the connector, thus sealing it via the aforementioned ball-and-cone connection.

[0019] At the end of the mating connector is a hermetically sealed corrugated protective sleeve. Inside this sleeve are wires for transmitting the electrical signals from the measuring coil.

[0020] At the end of the corrugated protective conduit is a hermetically sealed terminal box. This box contains terminals to which the wires coming from the measuring coil are connected. On the opposite side of these terminals, wires or cables are connected to carry the electrical signals to the driver electronics.

[0021] The connector and the mating connector's union nut are designed with a hole pattern. This pattern forms part of a locking mechanism between the connector and the mating connector. After the union nut has been tightened to a specific torque, several locking wires are threaded through the holes of the pattern on the connector and the mating connector, and the two wire ends are twisted together.

[0022] The connector element of the inductive sensor has at least one or more cooling fins to reduce the temperature. This is intended to protect components inside the connector element and the mating connector with corrugated tubing from high temperatures.

[0023] All components of the measuring system described above, with the exception of the driver electronics, consist entirely of inorganic materials. This means the measuring system is permanently radiation-resistant and does not age in radiation-exposed application areas. The aforementioned hermetic seal of the sensor as a single system, as well as the hermetic seal of the remaining components between the sensor and the terminal box, prevents the ingress of moisture into hot steam environments and other media, thus ensuring long-term functionality. The inductive sensor is hermetically sealed in both the plugged-in and unplugged states. AREA OF APPLICATION

[0024] The inductive sensor is suitable for measuring linear distances. One example would be the safety monitoring of the position of a pressure-reducing valve in a nuclear power plant inside the containment structure under high levels of radioactive radiation and high temperature. DRAWINGS Brief description of the drawings Fig. Figure 1 shows the connection element and the mating connector of the inductive sensor according to the invention in a cutaway isometric view. Fig. Figure 2 shows the entire measurement system without driver electronics in an isometric view. Fig. Figure 3 shows a cross-section through the entire measuring system. Fig. 2 in a side view with a detail view Z. Fig. Figure 4 shows a schematic sketch of the entire measuring system. DESCRIPTION OF THE EXECUTION EXAMPLE

[0025] In Fig. Figure 3 shows an inductive sensor according to the invention. This inductive sensor is used for detecting linear displacements. It has a housing H, consisting of a sensor housing 7 and a measuring coil carrier 6. A measuring coil 9 is arranged on the measuring coil carrier 6. A movable core 8 is inductively coupled to this measuring coil 9. This core is located within the measuring coil carrier 6 without contact in the axial direction relative to the measuring coil 9. 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 hermetically welded to each other at their contact points using a laser welding process, either axially or radially. The connection housing 1 has several bores in which a pin contact 4 is secured by means of a glass insert 5.The interior of the laser-welded assembly described so far, consisting of "connection housing 1", "measuring coil carrier 6", and "outer sensor housing 7", is thus completely hermetically sealed. The aforementioned pin contacts 4 are connected inside the sensor to the measuring coil 9 by means of several wires 12. A mating connector G, consisting of a mating connector housing 2, the mating connector 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 sleeve 10, which in turn is hermetically sealed to a terminal box 11. The measuring coil 9 is electrically connected to the terminal box 11 via the wires 12, the pin contacts 4, the mating connector contacts 14, and the wires 13. The terminal box 11 provides a connection point for wires around the driver electronics E (. Fig. 4) to connect. 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.

[0026] In Fig. Figure 1 shows the releasable connection between the connection element S, consisting of the connection housing 1, the pin contacts 4, and the glass insert 5, and the mating connector G, consisting of the mating connector housing 2, the union nut 3, and the mating connector contacts 14. This allows for easy and quick connection and disconnection of the mating connector G and all attached components from the inductive sensor. For a complete hermetic seal, the remaining space between the connection element S and the mating connector G, perpendicular to the longitudinal axis, must also be hermetically sealed. This is shown in detail view Z in Figure 1. Fig. As shown in Figure 3, this is achieved by a ball-and-cone connection. The connector housing 1 has an inwardly offset, circular cone, while the mating connector housing 2 has a spherical surface. Tightening the retaining nut 3 presses the spherical surface of the mating connector housing 2 into the cone of the connector housing 1. This creates a circular, tangential contact between the two components, as shown in detail view Z. With this type of seal, the geometry of both components is elastically deformed in the area of ​​the ball and the cone, and the tangential contact line becomes a contact surface. When this connection is released, the geometry of both connector components returns to its original state.

[0027] To maintain the contact pressure between the ball and cone permanently, the union nut 3 must be secured against loosening due to external influences such as vibration. This is achieved by using several locking wires. These are each threaded through a hole of the hole pattern P in the union nut 3 and a hole of the hole pattern P in the connection housing 1 and twisted together, so that there is no room for movement of the union nut 3 and it is effectively prevented from loosening on its own.

[0028] The connection housing 1 is as shown in Fig. Figure 1 is shown equipped with one or more cooling fins C. This advantageous design reduces heat transfer from the sensor housing towards the pin contacts 4, since the sensor housing can be mounted directly on very hot heat sources where the highest temperatures occur.

[0029] The material selection of 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 service life and reliability of the measuring system. REFERENCE MARK LIST 1 connection housing 2 mating connector housings 3 Union nuts 4 pin contacts 5 Glass pouring 6 measuring coil carriers 7 Sensor housings 8 cores 9 Measuring coil 10 Corrugated protective hose 11 terminal box 12 strands 13 strands 14 mating connector contact H housing consisting of 6 and 7 S connection element consisting of 1, 4 and 5 G mating connector consisting of 2, 3 and 14 E driver electronics C Cooling fins P Hole pattern T thread

Claims

Inductive sensor for detecting linear distances comprising a) a housing (H), b) a measuring coil (9) arranged in the housing (H), c) a movable core (8) inductively coupled to the measuring coil (9), d) a mating connector (G), e) and a connecting element (S) for electrically connecting the measuring coil (9) to the mating connector (G), characterized in that a hermetic longitudinal seal of the inductive sensor is provided by a glass encapsulation (5) of pin contacts (4) of the connecting element (S) and a hermetic transverse seal of the inductive sensor is provided by a ball-cone connection, wherein the connecting element (S) and the mating connector (G) are detachably connected by a thread (T), and the connecting element (S) and the mating connector (G) are each provided with a hole pattern (P) for screw locking. Inductive sensor according to claim 1, characterized in that the mating connector (G) is designed with a hermetically sealed corrugated protective hose (10). Inductive sensor according to claim 2, characterized in that the inductive sensor has a hermetically sealed terminal box (11) which is connected to the corrugated protective hose (10). Inductive sensor according to one of the preceding claims, characterized in that the connection element (S) has at least one cooling fin (C) for reducing the temperature.

Images