GB2592321A

GB2592321A - Sensor assemblies

Info

Publication number: GB2592321A
Application number: GB2105999.3A
Authority: GB
Inventors: Dear Nathan; Hiron-Jones Ben; Maskery Jeff
Original assignee: LONGVALE Ltd
Current assignee: LONGVALE Ltd
Priority date: 2021-04-27
Filing date: 2021-04-27
Publication date: 2021-08-25
Anticipated expiration: 2041-04-27
Also published as: GB202105999D0; GB2592321B

Abstract

Defining the axial position of a Reed switch sensor assembly 10 with a spacer 22. Preferably, a variety of differently sized spacers are available to precisely define the axial position needed (fig. 3 and fig. 5), this axial position then being fixed during manufacture. The sensor assembly has a body tube 18 (outer casing), a housing 16 and a blind bore 20. The housing is received in the blind bore of the body tube. A spacer is positioned in the blind bore and contacts the closed end of the blind bore 24. The Reed switch 14 is positioned in the housing. The housing is then seated on or in the spacer and depending on the size of spacer chosen the axial position of the housing and thus the Reed switch in the blind bore may be selectively defined. The assembly may also have a Mu-metal sleeve 26 which may cover parts of the housing to act as a shield. The sensor assembly may be a proximity sensor assembly.

Description

TITLE

Sensor Assemblies

TECHNOLOGICAL FIELD

Examples of the disclosure relate to sensor assemblies, and particularly sensor assemblies comprising a reed switch.

BACKGROUND

Sensor assemblies comprising a reed switch to detect the presence of magnetic targets are known. Such sensors are able to detect the presence of nearby magnetic targets without any physical contact. The use of such sensors in process control automation, such as the process of water flow in a hydrogen generating electrolysis plants is desirable. However, reed switches have inherent variability in their magnetic responsiveness. Accordingly, there is a desire to be better able to detect the position of a magnetic target accurately and in a number of different sensing directions.

BRIEF SUMMARY

According to various, but not necessarily all, examples of the disclosure there is provided a sensor assembly, the sensor assembly comprising a switch assembly, wherein the switch assembly comprises a reed switch received in a housing, wherein the sensor assembly comprises a body tube, wherein the housing is received in a blind bore of the body tube, wherein the sensor assembly comprises a spacer in the blind bore contacting the closed end of the blind bore, wherein the housing is seated on or in the spacer to selectively define the axial position of the housing and thus the reed switch in the blind bore.

The housing may be seated on or in the spacer in one of a plurality of different seating positions to selectively define different axial positions of the housing and thus the reed switch in the blind bore. The different seating positions may be provided by a ramped interface between the spacer and the housing. The ramped interface may be splined The sensor assembly may comprise one of a plurality of different spacers, each of which is dimensioned to selectively define a different axial position of the housing and thus the reed switch in the blind bore when the housing is seated on or in the spacer.

The sensor assembly may comprise a Mu-metal sleeve in the blind bore, wherein the sleeve selectively covers a part of the housing.

The Mu-metal sleeve may be seated on a shoulder of the housing. The Mu-metal sleeve may be seated on one of a plurality of shoulders of the housing to selectively cover different parts of the housing. The Mu-metal sleeve may by coupled to the housing. The Mu-metal sleeve may be coupled to the housing by an interference fit. The Mu-metal sleeve may be a foil wrapped onto the housing. The Mu-metal sleeve may comprise an opening or a plurality of openings therethrough. The sensor assembly may comprise a plurality of Mu-metal sleeves selectively covering different parts of the housing.

The sensor assembly may be a proximity sensor assembly.

According to various, but not necessarily all, examples of the disclosure there is provided a method of manufacturing a sensor assembly according to any of the preceding paragraphs, wherein the method comprises: providing the body tube comprising the blind bore; seating the housing on or in the spacer to selectively define the axial position of the housing and thus the reed switch in the blind bore.

According to various, but not necessarily all, examples of the disclosure there may be provided examples as claimed in the appended claims.

BRIEF DESCRIPTION

For a better understanding of various examples that are useful for understanding the detailed description, reference will now be made by way of example only to the accompanying drawings in which: Fig. 1 illustrates a part cross sectional view of a sensor assembly, Fig. 2 illustrates an exploded view of the sensor assembly of Fig.1; Fig. 3 illustrates a part cross sectional view showing only some of the components of another sensor assembly in a first condition; Fig. 4 illustrates a part cross sectional view showing only some of the components of the sensor assembly of Fig. 3 in a second condition; Fig. 5 illustrates a part cross sectional view showing only some of the components of another sensor assembly; Fig. 6 illustrates a cross sectional view showing only some of the components of another sensor assembly but also showing the magnetic field; Fig. 7 illustrates a cross sectional view showing only some of the components of another sensor assembly but also showing the magnetic field; and Fig. 8 illustrates a cross sectional view of a part of the sensor assembly of Fig. 1.

DETAILED DESCRIPTION

The figures illustrate a sensor assembly 10 and a method of manufacturing the sensor assembly 10.

The sensor assembly 10 comprises a switch assembly 12. The switch assembly 12 comprises a reed switch 14 received in a housing 16. The switch assembly 12 is a cartridge or capsule. The switch assembly 12 may also be referred to as a sensor element. The reed switch 14 is fixed in the housing 16. The reed switch 14 is constrained by the housing 16. The housing 16 may provide internal location means such as location slots to accurately and fixedly position the reed switch 14 within the housing 16. The housing 16 may be made of an insulating material such as plastics.

The housing 16 is an internal housing assembly.

A reed switch 14 enables the detection of nearby magnetic targets without any physical contact. The magnetic target may be external to the sensor assembly 10, such as mounted to a valve shaft, actuator piston or level float, or integral to the sensor assembly 10, such as attached to a paddle or float assembly in the form of a flow or level switch respectively. In some examples the sensor assembly is a proximity sensor assembly.

The sensor assembly comprises a body tube 18. The body tube 18 is an outer casing. The body tube 18 may be stainless steel. The housing 16 is received in a blind bore 20 of the body tube 18. The housing 16 is therefore comprised within the body tube 18. In some examples, the blind bore 20 has a uniform bore diameter. Accordingly, in such examples the blind bore 20 has straight sides. The blind bore 20 may be a cylindrical blind bore. The blind bore 20 is an inner blind bore. The housing 16 provides electrical insulation between the reed switch 14 contacts and wiring and the body tube 18.

The sensor assembly 10 comprises a spacer 22 in the blind bore 20 contacting the closed end 24 of the blind bore 20.

The housing 16 is seated on or in the spacer 22 to selectively define the axial position of the housing 16 and thus the reed switch 14 in the blind bore 20. Accordingly, the axial position of the housing 16 in the blind bore 20 can be precisely controlled and easily checked. The reed switch 14 is received in the housing 16 in a fixed position and thus the axial position of the reed switch 14 in the blind bore 20 is dependent on the axial position of the housing 16 and can therefore be precisely controlled.

The position of the housing 16, and consequently the reed switch 14, can therefore be selected according to the particular performance requirements of the sensor assembly 10 and taking into account the inherent variability in magnetic responsiveness associated with reed switches. For instance, the sensor assembly 10 may be required to detect a magnetic target approaching at a particular point along the length of the body tube 18 perpendicularly to the axis of the body tube 18. Accordingly, the position of the housing 16, and therefore the reed switch 14, can be selected to allow optimum detection of this magnetic target. For example, axial adjustment of the housing 16 by 10 mm using the spacer 22 will move the perpendicular focus of the reed switch 14 by 10 mm.

Alternatively, the sensor assembly 10 may be required to detect a magnetic target approaching axially but offset by a distance from the axis of the sensor assembly 10. Accordingly, the position of the housing 16, and therefore the reed switch 14, can be selected to allow optimum detection of this magnetic target.

Accordingly, examples of the disclose are better able to detect the position of a magnetic target accurately and in a number of different sensing directions by axial adjustment of the position of the housing 16, and consequently the reed switch 14, in the blind bore 20 of the body tube 18. Examples of the disclosure allow precise axial adjustment of the position of the housing 16, and consequently of the reed switch 14, in the blind bore 20 to define an optimised sensing window for a particular application. Accordingly, axial adjustment of the reed switch 14 in the blind bore 20 provides a different focus point of the reed switch 14 along the length of the body tube 18.

The spacer 22 may be referred to as a collar or position adaptor. The spacer 22 may be made of an insulating material, such as plastics.

Sensor assembly 10 according to examples of the disclosure are useable in process control automation, such as the process of water flow in a hydrogen generating electrolysis plant, for example in relation to process control valves and level detection devices. The abovementioned advantages of examples of the disclosure result in an overall more efficient and less costly process.

In some examples, the housing 16 is seated on or in the spacer 22 in one of a plurality of different seating positions to selectively define different axial positions of the housing 16 and thus the reed switch 14 in the blind bore 20. Fig. 3 illustrates a first condition of the sensor assembly 10 wherein the housing 16 is seated on or in the spacer 22 in a first seating position. Fig. 4 illustrates a second condition of the sensor assembly 10 wherein the housing 16 is seated on or in the spacer 22 in a second seating position.

The axial position of the housing 16, and therefore of the reed switch 14, is different in the first and second conditions of the sensor assembly 10.

The different seating positions may be provided by a ramped interface 23 between the spacer 22 and the housing 16 as illustrated in the drawings.

The ramped interface 23 may be a spiral ramped interface. The ramped interface 23 may be comprised of corresponding ramped engagement surfaces 25 on the respective interacting ends 29, 31 of the housing 16 and spacer 22. The corresponding ramped engagement surfaces 25 may be threaded. Accordingly, rotation of the spacer 22 and/or the housing 16 causes a change in the axial position of the housing 16 according to the profile of the ramped interface 23. Accordingly, the mated length of the spacer 22 and the housing 16 depends on the relative position of the spacer 22 and housing 16 about the ramped interface 23. The interacting ends 29, 31 are mated during manufacture according to a required seating position. In use, the angular correspondence is maintained between the ramped engagement surfaces 25, for example, by a press fit. Accordingly, there is no relative movement between the spacer 22 and housing 16 after the seating position has been set.

In some examples, the ramped interface may be splined. The splined ramped interface may be comprised of corresponding splined ramped engagement surfaces on the respective interacting ends 29, 31 of the housing 16 and spacer 22. The splined ramped engagement surface on one of the interacting ends 29, 31 comprises ridges or teeth. The splined ramped engagement surface on the other of the interacting ends 29, 31 comprises groves. The interacting ends 29, 31 are mated during manufacture according to a required seating position. In use, the angular correspondence is maintained between the splined ramped engagement surfaces at the splined ramped interface by the ridges mating with the grooves. Accordingly, there is no relative movement between the spacer 22 and housing 16 after the seating position has been set.

The spacer 22 is configured such that the housing 16 can be seated on or in the spacer 22 in a seating position selectively defining an axial position where the housing 16 is spaced from the closed end 24 of the blind bore 20.

In some examples, the spacer 22 is also configured such that the housing 16 can be seated on or in the spacer 22 in a seating position selectively defining an axial position where the housing 16 contacts the closed end 24 of the blind bore 20, or the bottom of the housing 16 is flush with the bottom of the spacer 22. In such a configuration the spacer 22 may be wound fully up the ramped engagement surface 25 of the housing 16.

The sensor assembly 10 may comprise one of a plurality of different spacers 22, each of which is dimensioned to selectively define a different axial position of the housing 16, and thus the reed switch 14, in the blind bore 20 when the housing 16 is seated on or in the spacer 22. Fig. 5 illustrates and example in which the spacer 22 is enlarged compared to the spacer 22 of the sensor assembly 10 of Figs. 3 and 4, and therefore selectively defines a different axial position of the housing 16 and thus the reed switch 14 in the blind bore 20. The enlarged spacer 22 of Fig 5 has a greater axial length than the spacer 22 of Figs. 3 and 4. Accordingly, the sensor assembly 10 may comprise one of a plurality of different spacers 22. The plurality of spacers 22 differ in terms of their axial length.

In some examples, the sensor assembly comprises a Mu-metal sleeve 26 in the blind bore 20. In some examples, the Mu-metal sleeve 26 consists of Mu-metal.

The Mu-metal sleeve 26 selectively covers a part of the housing 16. According, the Mu-metal sleeve 26 is received in the blind bore 20. The Mu-metal sleeve 26 may be referred to as a shim. The Mu-metal sleeve 26 may be referred to as a shroud.

In some examples, the Mu-metal sleeve 26 may be seated on a shoulder 28 of the housing 16. The Mu-metal sleeve 26 may be seated on one of a plurality of shoulders 28 of the housing 16 to selectively cover different parts of the housing 16. Accordingly, the Mu-metal sleeve 26 may be located at a plurality of different positions on the housing 16.

The Mu-metal sleeve 26 may by coupled to the housing 16. Accordingly, the Mu-metal sleeve 26 may contact the housing 16. In some examples, the Mu-metal sleeve 26 is coupled to the housing 16 by an interference fit. The Mu-metal sleeve 26 may be a foil. The foil is wrapped onto the housing 16 in a required position. The foil may have a thickness of 0.15 mm. The foil may be an adhesive foil. In some examples, the Mu-metal sleeve 26 has a constant thickness. In other examples, the Mu-metal sleeve 26 has a variable thickness.

Mu-metal is a soft magnetic alloy with exceptionally high magnetic permeability. The high permeability of Mu-metal provides a low reluctance path for magnetic flux.

As a magnetic target approaches a reed switch 14 it creates a magnetic field 27 around the reed switch 14 with centre lopes and outer lopes as illustrated in Fig. 6.

The Mu-metal sleeve 26 acts as a magnetic shield against the magnetic field 27 about an area of the housing 16 covered by the Mu-metal sleeve 26. Accordingly, the magnetic field 27 in examples in which the sensor assembly 10 comprises a Mu-metal sleeve 26 is focused, for example as illustrated in Fig. 7. In each of Figs. 6 and 7, as a magnetic target is presented to the reed switch 14, the magnetic field 27 will change state from the dashed lines to the solid lines.

The Mu-metal sleeve 26 works by providing a path for the magnetic field 27 around the shielded area, thus in Fig. 7 the magnetic field 27 is focused or directed out of one end 29 of the sensor assembly 10 towards a magnetic target, thus optimising sensing distance and/or direction. In other examples, the Mu-metal sleeve 26 may be positioned at or towards one end of the housing 16 and thus the magnetic field 27 will be focused or directed out of a side of the sensor assembly 10 (i.e., perpendicular to the axis of the body tube 18) towards a magnetic target, thus optimising sensing distance and/or direction.

Accordingly, examples of the disclosure enable windowing of the detection area via positioning of the Mu-metal sleeve 26 to detect the presence of a magnetic target in a precise sensing window. Furthermore, 'double switching' where a magnetic target can pass through the magnetic field 27 and trigger a secondary undesirable switch event can be prevented.

The Mu-metal sleeve 26 may be cylindrical. The Mu-metal sleeve 26 may be tubular or part tubular. The Mu-metal sleeve 26 may be in one or a plurality of bands to provide a required sensing window. Accordingly, sensor assemblies 10 according to some examples of the disclosure comprise a plurality of Mu-metal sleeves 26 selectively covering different parts of the housing. The plurality of Mu-metal sleeves 26 are arranged to define a plurality of different sensing window. The Mu-metal sleeve 26 may be dimensioned to provide a required sensing windowing. The Mu-metal sleeve 26 may comprise an opening or a plurality of openings therethrough to provide a required sensing window or windows.

Sensor assemblies 10 according to some examples of the disclosure may be mounted adjacent to or surrounded by ferrous metals without affecting the sensing distance because the Mu-metal sleeve 26 prevents magnetic field 27 from being lost to the adjacent or surrounding ferrous metal. Accordingly, the Mu-metal sleeve 26 stops surrounding ferrous metal from robbing flux and reducing the sensing range. Accordingly, the Mu-metal sleeve 26 provides shielding from surrounding magnetic flux in examples where a sensor assembly 10 is screwed into a valve or actuator mounting hole surrounded by ferrous material. The Mu-metal sleeve 26 will also protect the reed switch 14 from the external influence of magnets.

In some examples the sleeve 26 is formed of a different metal with high magnetic permeability. Accordingly, sensor assemblies 10 according to some examples of the

disclosure comprise a metallic sleeve 26.

As illustrated in Fig. 8, in some examples the blind bore 20 extends from the closed end 24 to an open end 30. The open end 30 connects with a body tube cavity 32. The body tube cavity 32 extends to an end 34 of the body tube 18. In the illustrated example the body tube cavity 32 has a diameter larger than the diameter of the blind bore 20. The body tube cavity 32 has a non-uniform diameter. The diameter of the body tube cavity 32 increases towards the end 34 of the body tube 18. The body tube cavity 32 is provided within an area 36 of the body tube 18. In the illustrated example, the area 36 is an enlarged area 36 and has the form of a bolt head, such as a standard hex-head bolt head. Accordingly, in some examples the body tube 18 is an elongate hollow tubular member comprising the blind bore 20 and the body tube cavity 32. In the illustrated example, solder pads 42 are provided on a printed circuit board, wherein the printed circuit board is attached to the reed switch 14. Electrical wires extending from the solder pads may be combined in a single cable 48, or may be provided in separate cables 48. In other examples, the electrical wires may extend directly from the reed switch 14 itself rather than from a printed circuit board. The electrical wires are arranged for being connected with control and/or sensing circuits elsewhere. The electrical wires extend through the body tube cavity 32 and out of the end 34 of the body tube 18. As is conventional, the switch assembly 12 may be hermetically sealed within the body tube 18 using an epoxy resin to provide an end seal assembly 50, i.e., potting. Alternatively, a glass hermetic seal and potting compound may be provided as an end seal assembly 50. The potting fixes and seals internal components. The potting substantially fills the body tube cavity 32.

In use, a controller (not illustrated) is configured to continuously supply an electrical input signal to the sensor assembly 10, and to monitor the electrical output signal using the control and/or sensing circuits. By monitoring the electrical output signal, it can be determined whether or not a magnetic target is within the sensing range of the sensor assembly 10.

In one none limiting example, the opening and closing of a valve causes a magnetic target to move in and out of the sensing range. Thus, by monitoring the electrical output signal it can be determined whether the valve is open or closed.

A method of manufacturing a sensor assembly 10 according to examples of the disclosure is also provided.

The method comprises providing the body tube 18 comprising the blind bore 20.

The method comprises seating the housing 16 on or in the spacer 22 to selectively define the axial position of the housing 16 and thus the reed switch 14 in the blind bore 20. Accordingly, the axial position of the housing and thus the reed switch 14 in the blind bore 20 is determined during the manufacture of the sensor assembly 10.

The housing 16 may be seated on or in the spacer 22 and then the mated assembly inserted into the blind bore 20 such that the spacer 22 contacts the closed end 24 of the blind bore 20. Alternatively, the spacer 22 may be inserted into the blind bore 20 such that the spacer 22 contacts the closed end 24 of the blind bore 20 and subsequently the housing 16 is inserted and seated on the spacer 22.

The spacer 22 and the sleeve 26 are separately manufactured parts The method may comprise forming the blind bore 20 by a drilling operation. The method may also comprise providing a body tube 18 comprising a body tube cavity 32 by a drilling operation. Accordingly, the method comprises forming a body tube cavity 32 by a drilling operation.

There is thus described a reed sensor assembly 10 and a method of manufacture with a number of advantages as described above.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, the housing 16 may comprise Mu-metal in one or more areas to provide a required sensing window in areas of the housing 16 not comprising Mu-metal.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

The term "comprise" is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use "comprise" with an exclusive meaning then it will be made clear in the context by referring to "comprising only one..." or by using "consisting".

In this brief description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term "example" or "for example" or "may" in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus "example", "for example" or "may" refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that comprise some but not all of the instances in the class. It is therefore implicitly disclosed that features described with reference to one example but not with reference to another example, can where possible be used in that other example but does not necessarily have to be used in that other example.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

15 20 25 30

Claims

CLAIMS1. A sensor assembly, the sensor assembly comprising a switch assembly, wherein the switch assembly comprises a reed switch received in a housing, wherein the sensor assembly comprises a body tube, wherein the housing is received in a blind bore of the body tube, wherein the sensor assembly comprises a spacer in the blind bore contacting the closed end of the blind bore, wherein the housing is seated on or in the spacer to selectively define the axial position of the housing and thus the reed switch in the blind bore.
2. A sensor assembly according to claim 1, wherein the housing is seated on or in the spacer in one of a plurality of different seating positions to selectively define different axial positions of the housing and thus the reed switch in the blind bore.
3. A sensor assembly according to claim 2, wherein the different seating positions are provided by a ramped interface between the spacer and the housing.
4. A sensor assembly according to claim 3, wherein the ramped interface is a splined.
5. A sensor assembly according to any of the preceding claims, wherein the sensor assembly comprises one of a plurality of different spacers, each of which is dimensioned to selectively define a different axial position of the housing and thus the reed switch in the blind bore when the housing is seated on or in the spacer.
6. A sensor assembly according to any of the preceding claims, wherein the sensor assembly comprises a Mu-metal sleeve in the blind bore, wherein the sleeve selectively covers a part of the housing.
7. A sensor assembly according to claim 6, wherein the Mu-metal sleeve is seated on a shoulder of the housing
8. A sensor assembly according to claims 6 or 7, wherein the Mu-metal sleeve is seated on one of a plurality of shoulders of the housing to selectively cover different parts of the housing.
9. A sensor assembly according to an of claims 6 to 8, wherein the Mu-metal sleeve is coupled to the housing.
10. A sensor assembly according to claim 9, wherein the Mu-metal sleeve is coupled to the housing by an interference fit.
11. A sensor assembly according to any of claims 6 to 10, wherein the Mu-metal sleeve is a foil wrapped onto the housing.
12. A sensor assembly according to any of claims 6 to 11, wherein the Mu-metal sleeve comprises an opening or a plurality of openings therethrough.
13. A sensor assembly according to any of claims 6 to 12, wherein the sensor assembly comprises a plurality of Mu-metal sleeves selectively covering different parts of the housing.
14. A sensor assembly according to any of the preceding claims, wherein the sensor assembly is a proximity sensor assembly.
15. A method of manufacturing a sensor assembly according to the preceding paragraphs, wherein the method comprises: providing the body tube comprising the blind bore; seating the housing on or in the spacer to selectively define the axial position of the housing and thus the reed switch in the blind bore.