Switch box

Abstract

Switch box comprising a housing, a first shaft part 201, a second shaft part 301, a rotatable indicator 401 and one or more friction devices 160, 162. The housing comprises first and second housing po

Description

TECHNOLOGICAL FIELD Examples of the disclosure relate to a switch box. Some relate to a switch box for housing one or more sensors / switches which sense the position of a valve in a hazardous environment. BACKGROUND Valves may operate in hazardous environments, for example, in hydrocarbon or hydrogen processing plants. Flammable gases may be present in the environment. Electrical equipment located in such an environment can provide an ignition source, potentially creating a hazard. One or more sensors / switches may sense whether a valve is in an open state or a closed state. The valve may, for example, control the routing of fluid within a pipe in a hazardous environment. The switch(es) may be located in a switch box which is flameproof, explosion proof and / or intrinsically safe. BRIEF SUMMARY According to various, but not necessarily all, examples there is provided a switch box, comprising: a housing comprising at least a first housing portion and a second housing portion, the first and second housing portions being connectable to define a chamber for housing one or more switches, wherein: the first housing portion comprises an aperture; and the second housing portion comprises an aperture; a first shaft part, located at least partially in the aperture in the first housing portion and extending into the chamber, operatively connectable to an actuator for rotating first shaft part; a second shaft part located at least partially in the aperture in the second housing portion and is removably connectable to the first shaft part such that the first and second shaft parts corotate when the first shaft part is rotated; a rotatable indicator, arranged to visually indicate a state of opening of a valve, connectable to the second shaft part such that the rotatable indicator corotates with the second shaft part, and such that the rotatable indicator rotates with the first shaft part when the first and second shaft parts are connected; and one or more friction devices for resisting the rotation of the rotatable indicator and the second shaft part, when the second shaft part is disconnected from the first shaft part. At least one friction device of the one or more friction devices may be arranged to contact the second shaft part when the second shaft part is rotated. The second housing portion may comprise a bushing. The second shaft part may be partially located within the bushing and may be arranged to rotate within the bushing. The at least one friction device may be arranged to contact the bushing when the second shaft part is rotated. The bushing may be at least partially located within the aperture of the second housing portion. The at least one friction device may be located at least partially within the aperture of the second housing portion. The at least one friction device may be located within the bushing. The second shaft part may comprise a curved outer surface. The at least one friction device may be arranged to contact the curved outer surface of the second shaft part when the second shaft part is rotated. The bushing may have a curved inner surface. The friction device may be arranged to contact the curved inner surface when the second shaft part is rotated. The at least one friction device may be located around the second shaft part. The second shaft part may comprise a recess. The at least one friction device may be located in the recess. The recess may be a circumferential recess in a curved outer surface of the second shaft part. The at least one friction device may be ring-shaped. The at least one friction device may be located at least partially outside the aperture of the second housing portion. The at least one friction device may be located at least partially outside the bushing. The one friction device may be arranged to contact the bushing outside the aperture of the second housing portion. The second shaft part may comprise a recess. The at least one friction device may be located in the recess. The second shaft part may comprise a flange. The recess may be located in the flange. The recess may be located in a substantially planar surface of the flange. The at least one friction device may be ring-shaped. The one or more friction devices may be formed from at least one resilient material. The at least one resilient material may comprise at least one polymer. The second shaft part may be directly connectable to the first shaft part. The second shaft part may be directly connectable to the first shaft part by a male-female connection. The second shaft part may be fixedly connected to the rotatable indicator, such that the rotatable indicator corotates with the second shaft part. When the rotatable indicator is connected to the second shaft part, and the second shaft part is connected to the first shaft part, the rotatable indicator, the second shaft part and the first shaft part may be arranged to rotate about the same axis of rotation. According to various, but not necessarily all, examples there is provided a switch box, comprising: a housing comprising at least a first housing portion and a second housing portion, the first and second housing portions being connectable to define a chamber for housing one or more switches, wherein: the first housing portion comprises an aperture; and the second housing portion comprises an aperture; a first shaft part, located partially in the aperture in the first housing portion and extending into the chamber, operatively connectable to an actuator for rotating first shaft part; a second shaft part, located partially in the aperture in the second housing portion and extending into the chamber, wherein the second shaft part is removably connectable to the first shaft part such that the first and second shaft parts corotate when the first shaft part is rotated; and a rotatable indicator, arranged to visually indicate a state of opening of a valve, connectable to the second shaft part such that the rotatable indicator corotates with the second shaft part, and such that the rotatable indicator rotates with the first shaft part when the first and second shaft parts are connected. The aperture in the second housing portion may be located in a wall of the second housing portion. The wall may have an inner surface that at least partially defines the chamber. The second shaft part may extend beyond the inner surface into the chamber. In use, the first housing portion may be a lower housing portion, the second housing portion may be an upper housing portion, the wall of the upper housing portion may be a roof, and the inner surface may provide at least part of a ceiling of the chamber. The second shaft part may comprise a flange. When the first housing portion is connected to the second housing portion, the flange may be located in the chamber. The flange may be located adjacent the inner surface of the wall of the second housing portion. The switch box may further comprise at least one seal located around and in contact with the second shaft part. The second shaft part may comprise a recess. The at least one seal may be partially located in the recess. The recess may be a circumferential recess in the curved outer surface of the second shaft part. The second housing portion may comprise a bushing. The second shaft part may be partially located within the bushing and may be arranged to rotate within the bushing. The at least one seal may be arranged to contact the bushing. The bushing may be at least partially located within the aperture of the second housing portion. The second shaft part may extend beyond the bushing into the chamber. The at least one seal may be located within the bushing. The at least one seal may be located at least partially outside the aperture of the second housing portion. The second housing portion may comprise a bushing. The second shaft part may be partially located within the bushing and may be arranged to rotate within the bushing. The at least one seal may be located outside the bushing and may be arranged to contact the bushing. The at least one seal may be arranged to contact the bushing outside the aperture of the second housing portion. The bushing may provide at least part of the ceiling of the chamber. The at least one seal may be arranged to contact the bushing at the ceiling of the chamber. The at least one seal may be partially located in a recess in the flange. The recess may be located in a substantially planar surface of the flange. The at least one seal may be ring-shaped. The seal may be formed from at least one resilient material. The at least one resilient material may comprise at least one polymer. The second shaft part may be directly connectable to the first shaft part. The second shaft part may be directly connectable to the first shaft part by a male-female connection. The second shaft part may be fixedly connected to the rotatable indicator, such that the rotatable indicator corotates with the second shaft part. When the rotatable indicator is connected to the second shaft part, and the second shaft part is connected to the first shaft part, the rotatable indicator, the second shaft part and the first shaft part may be arranged to rotate about the same axis of rotation. According to various, but not necessarily all, examples there is provided a switch box, comprising: a housing comprising at least a first housing portion and a second housing portion, the first and second housing portions being connectable to define a chamber for housing one or more switches, wherein: the first housing portion comprises an aperture; and the second housing portion comprises an aperture; a target carrier, comprising an aperture and locatable in the chamber, arranged to carry at least one target for causing actuation of at least one of the one or more switches housed in the chamber; a support for supporting the target carrier in the chamber; a rotatable shaft, extendable through the aperture in the target carrier and comprising a flange, the rotatable shaft being separable into a first shaft part and a second shaft part, wherein: the first shaft part is located partially in the aperture in the first housing portion, extends into the chamber, and is operatively connectable to an actuator for rotating first shaft part; the second shaft part is located partially in the aperture in the second housing portion and is removably connectable to the first shaft part such that the first and second shaft parts corotate when the first shaft part is rotated; and the flange is configured to resist movement of the target carrier away from the support when the first and second shaft parts are connected and the rotatable shaft extends through the aperture in the target carrier; and a rotatable indicator, arranged to visually indicate a state of opening of a valve, connectable to the second shaft part such that the rotatable indicator corotates with the second shaft part, and such that the rotatable indicator rotates with the first shaft part when the first and second shaft parts are connected. The target carrier may be locatable on the support. The support may be supported by the rotatable shaft. The support may be supported by the first shaft part. The support may be arranged to rotate with the rotatable shaft. The support may be configured to extend through an aperture in the rotatable shaft. The second shaft part may comprise the flange. The rotatable shaft may be arranged to rotate about an axis, The flange may be arranged to configured to resist movement of the target carrier along the axis and away from the support. The target carrier may be configured to abut the flange. The aperture of the second housing portion may be located in a wall of the second housing portion. When the first shaft part is connected to the second shaft part, the flange may be located between the aperture in the wall of the second housing portion and the target carrier. The flange may be arranged to support a friction device that is arranged to contact the wall of the second housing portion when the rotatable shaft is rotated. The flange may comprise a recess. The friction device may be partially located in the recess. The recess may be located in a substantially flat surface of the flange. The friction device may be ring-shaped. The friction device may be located at least partially outside the aperture of the second housing portion. The second housing portion may comprise a bushing. The second shaft part may be partially located within the bushing and may be arranged to rotate within the bushing. The friction device may be arranged to contact the bushing when the second shaft part is rotated within the bushing. The bushing may be at least partially located within the aperture of the second housing portion. The friction device may be located at least partially outside the bushing. The friction device may be formed from at least one resilient material. The at least one resilient material may comprise at least one polymer. The second shaft part may be directly connectable to the first shaft part. The second shaft part may be directly connectable to the first shaft part by a male-female connection. The second shaft part may be fixedly connected to the rotatable indicator, such that the rotatable indicator corotates with the second shaft part. When the rotatable indicator is connected to the second shaft part, and the second shaft part is connected to the first shaft part, the rotatable indicator, the second shaft part and the first shaft part are arranged to rotate about the same axis of rotation. While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate. The description of a function should additionally be considered to also disclose any means suitable for performing that function BRIEF DESCRIPTION Some examples will now be described with reference to the accompanying drawings in which: FIG. 1A illustrates an exploded view of part of a switch box including a first housing portion and a first shaft part; FIG. 1B illustrates an exploded view of part of the switch box including a second housing portion, a second shaft part and a rotatable indicator; FIG. 2A illustrates an exploded view of a shaft including the first shaft part and the second shaft part; FIG. 2B illustrates a cross-section of the shaft through the line A-A shown in FIG. 2C; FIG. 2C illustrates a front elevation of the shaft; FIGs.3A and 3B illustrate upper and lower perspective views of the first housing portion connected to the first shaft part; FIGs 4A and 4B illustrate upper and lower perspective views of the second housing portion connected to the second shaft part; FIG. 5A illustrates a plan view of an example of the switch box; FIG. 5B illustrates a cross-section of the switch box shown in FIG. 5A, taken through the line marked C-C in FIG. 5A; FIG. 6A illustrates an exploded view of the shaft and a target carrier; FIG. 6B illustrates a cross section of the shaft and the target carrier through the line A-A shown in FIG. 6C; FIG. 6C illustrates a front elevation of the shaft and the target carrier; FIG. 7A illustrates a plan view of a further example of the switch box; FIG. 7B illustrates a cross-section of the switch box shown in FIG. 7A, taken through the line marked D-D in FIG. 7A; and FIG. 7C illustrates a magnified portion of the cross-section of the switch box shown in FIG. 7B. The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures. DETAILED DESCRIPTION Embodiments of the invention relate to a switch box. The switch box may be for use in a hazardous environment, such as in a hydrocarbon or hydrogen processing plant. Flammable gases may be present in the hazardous environment. The switch box may be for use in a non-hazardous environment. The switch box might be for use inland, or in a coastal or subsea environment. The switch box may comprise a housing for housing sensors / switches that might sense a state of opening of a valve (e.g., whether a valve is in a fully open state, a partially open state or a closed state). The valve may, for example, be a process control valve. While the term “switch” is used predominantly in this document, the term “sensor” is considered to be synonymous in this context and could be used in place of the term “switch”. The switches may, for example, be magnetic proximity switches that provide an electrical output which indicates whether the valve is in a fully open state, a partially open state or a closed state. The switch box may include a rotatable indicator that is configured to visually indicate the state of opening of the valve (e.g., whether the valve is in the open state, a partially open state or the closed state). A shaft may extend through the housing and connect to the rotatable indicator. In use, an actuator for opening and closing the valve may be operatively connected to the shaft, causing rotation of the shaft when the valve is opened or closed. Such rotation of the shaft may cause concomitant rotation of the rotatable indicator which visually indicates whether the valve is open or closed. The shaft may be disconnectable into first and second shaft parts, and the housing may be disconnectable into at least a first housing portion and a second housing portion. When the first and housing portions are disconnected from one another, the first and second shaft parts may be disconnected from one another, such that the first shaft part is retained by the first housing portion and the second shaft part is retained by the second housing portion. The switch box includes one or more friction devices that resist rotation of the rotatable indicator when the firstand second housing portions (and therefore also the first and second shaft parts) are disconnected. Advantageously, this enables the first and second housing portions to be easily re-connected. This is described in further detail below. The second shaft part may extend into a chamber defined by the first and second housing portions. Advantageously, this enables a user (e.g., a technician) to easily orient the second shaft part to enable the first shaft part to be connected to the second shaft part. Each switch located inside the housing may be configured to change state in the presence of a target. One or more such targets may be located on a target carrier which may, for example, be mounted on the shaft inside the housing. A support, such as a support pin, may be located on the shaft to support the target carrier. The shaft may include a flange which might resist movement of the target carrier away from the support in presence of external forces on the switch box (e.g., vibratory forces). This may advantageously avoid a sensing malfunction due to movement of the targets relative to the switches in response to the external forces. This is explained in further detail below. FIG. 1A illustrates an exploded view of part of a switch box including a first housing portion 101 and a first shaft part 201. The first housing portion 101 comprises an aperture 102. The aperture 102 is for receiving and retaining the first shaft part 201. The first housing portion 101 is connectable to a second housing portion (not shown in FIG. 1A) to define a chamber 115 for housing one or more switches. In use, the first housing portion 101 may be a lower housing portion 101 and the second housing portion may be an upper housing portion. The first housing portion 101 comprises a floor 103 and walls 104-107. The walls 104-107 extend around the periphery of the floor 103 and extend (upwardly) away from the floor 103. The floor 103 provides the floor 103 of the chamber 115 defined by the first housing portion 101 and the second housing portion. Each of the walls 104-107 may provide at least part of a side wall of the chamber 115. In the illustrated example, the aperture 102 is located in the floor 103. The first housing portion 101 has a lip 108 from which a flange 109 extends. In the illustrated example, the flange 109 extends from the lip in a direction that is substantially perpendicular to the direction from which the walls 104-107 extend from the floor 103. The flange 109 provides a ledge on which the second housing portion can be located. The flange 109 defines one or more fixing locations 111 at which the first housing portion 101 can be fixed to the second housing portion. In this example, each of the fixing locations 111 comprises an aperture. Each aperture may be for receiving a fastener. Each aperture may, for example, be a threaded aperture for receiving a threaded fastener, such as a bolt. The first housing portion 101 may define one or more mounting locations 110 for mounting one or more switches / sensors within the chamber 115. Each switch may be for sensing a position of a valve. The one or more mounting locations 110 may be located on the floor 103 of the chamber 115. In the illustrated example, the one or more mounting locations 110 comprise one or more mounting apertures in the floor 103. The first shaft part 201 is connectable to a second shaft part (not shown in FIG. 1A). The first shaft part 201 is locatable at least partially in the aperture 102, such that the first shaft part 201 extends into the chamber 115. A washer 112, a seal 113 and a retainer 114 are illustrated in FIG. 1A. The seal 113 may be formed from a resilient material. In this regard, the seal 113 may be formed from at least one polymer. The seal 113 may be ring-shaped. The seal 113 is an O-ring seal in the illustrated example. The seal 113 is arranged to be located around the first shaft part 201 adjacent and underneath the aperture 102 in order to prevent or mitigate the ingress of dust or fluids (e.g., water) into the chamber 115. The retainer 114 is arranged to be located around the first shaft part 201 and above the aperture 102. In the illustrated example, the retainer 114 is a circlip. The retainer 114 is configured to retain the first shaft part 201 in the aperture 102 and prevent the first shaft part 201 from dropping out of the aperture 201 under the influence of gravity. FIG. 1B illustrates an exploded view of part of the switch box including the second housing portion 151, a second shaft part 301 and a rotatable indicator 401. The second housing portion 151 comprises an aperture 152. The aperture 152 is for receiving and retaining the second shaft part 301. The second housing portion 151 comprises an upper wall / roof 153 and walls 154-157. The walls 154-157 extend around the periphery of the upper wall 153 and extend (downwardly) from the upper wall 153. The upper wall 153 provides the upper wall / roof of the chamber 115 that is defined when the first and second housing portions 101, 151 are connected. Each of the walls 154-157 may provide at least a part of a side wall of the chamber 115. In the illustrated example, the aperture 152 is located in the upper wall 153. The upper wall 153 has an inner surface that at least partially defines the chamber 115. The inner surface provides at least part of a ceiling of the chamber 115. The aperture 152 is also provided in a boss that protrudes from an exterior surface of the upper wall 153. The second housing portion 151 has a lip (not shown in FIG. 1B) from which a flange 159 extends. In the illustrated example, the flange 159 extends from the lip in a direction that is substantially perpendicular to the direction from which the walls 154-157 extend from the upper wall 153. The flange 159 of the second housing portion 151 is arranged to be located on the flange 109 of the first housing portion 101. In this example, the flange 159 of the second housing portion 151 contacts the flange 109 of the first housing portion 101 when located thereon. The flange 159 defines one or more fixing locations 171 at which the second housing portion 151 can be fixed to the first housing portion 101. In this example, each of the fixing locations 171 comprises an aperture. Each aperture may be for receiving a fastener 171. Each aperture may, for example, be a threaded aperture for receiving a threaded fastener, such as a bolt. The fixing locations 111 of the first housing portion 101 may be aligned with the fixing locations 171 of the second housing portion 151 to enable the first and second housing portions 101, 151 to be fixed together. The rotatable indicator 401 is arranged to visually indicate a state of opening of a valve (e.g., whether the valve is in an open state, a partially open state or a closed state). The switch box comprises a cover 408 for the rotatable indicator 401. The upper wall 153 of the second housing portion 151 may comprise one or more fixing locations 164 at which the cover 408 may be fixed to the upper wall 153. The fixing locations 164 may be spaced from the aperture 152 and located around the aperture 152. The fixing locations 164 may, for example, be apertures, such as threaded apertures. The cover 408 may comprise one or more fixing locations 405 for use in fixing the cover 408 to the upper wall 153 of the second housing portion 151. The fixing locations 405 may be apertures. Each aperture may be a threaded aperture. The fixing locations 164 of the upper wall 153 may be aligned with the fixing locations 405 of the cover 408, when fixing the cover 408 to the upper wall 153. One or more fasteners, such as one or more threaded fasteners (e.g,, one or more bolts), may be used to fix the cover 408 to the upper wall 153. The rotatable indicator 401 may include text and / or graphics 402 which visually indicate the state of opening of a valve. The rotatable indicator 401 is shaped to be located inside the cover 408, and is arranged to rotate relative to (and inside) the cover 408. At least a portion of the cover 408 may be substantially transparent to enable the text and / or graphics 402 to be seen through the cover 408. The rotatable indicator 401 is arranged to be fixedly connected to the second shaft part 301, such that the rotatable indicator 401 co-rotates with the second shaft part 301, and such that the rotatable indicator 401 rotates with the first shaft part 201 when the first and second shaft parts 201, 301 are connected. When the rotatable indicator 401 is connected to the second shaft part 301, and the second shaft part 301 is connected to the first shaft part 201, the rotatable indicator 401, the second shaft part 301 and the first shaft part 201 are arranged to rotate about the same axis of rotation. The axis of rotation extends along the longitudinal dimension of each of the first shaft part 201 and the second shaft part 301. The switch box may comprise a retainer 163 that is configured to retain the second shaft part 301 in the aperture 152 in the second housing portion 151. The retainer 163 is arranged to be located around the second shaft part 301 and above the aperture 152. In the illustrated example, the retainer 163 is a circlip. The retainer 163 is configured to retain the second shaft part 301 in the aperture 152 and prevent the second shaft part 301 from dropping out of the aperture 152 under the influence of gravity. The switch box may comprise one or more friction devices / seals 160, 162 which may mitigate or prevent the ingress of fluids (e.g., flammable gases) into the chamber 115. Each of the friction devices / seals 160, 162 may be formed from a resilient material. In this regard, each of the friction devices / seals 160, 162 may be formed from at least one polymer. Each of the friction devices / seals 160, 162 may be ring-shaped. It should be borne in mind, however, that in some implementations the one or more friction devices 160, 162 might be different and might not perform a sealing function. For example, each of the one or more friction devices could be a washer, such as a fibre washer or a felt washer. Further functionality of the one or more friction devices / seals 160, 162 is described below. FIG. 2A illustrates an exploded view of a shaft 250 including the first shaft part 201 and the second shaft part 301. FIG. 2B illustrates a cross-section of the shaft 250 through the line A-A shown in FIG. 2C. FIG. 2C illustrates a front elevation of the shaft 250. While the first shaft part 201 is shown as being larger than the second shaft part 301 in FIGs 2A, 2B and 2C, this might not be the case in other examples. For instance, the second shaft part 301 might be substantially the same size as, or larger than, the first shaft part 201. The first shaft part 201 is removably connectable to the second shaft part 301. The first shaft part 201 and the second shaft part 301 may be connected to each other such that they are fixed to one another. The connection between the first shaft part 201 and the second shaft part 301 is removable in the sense that the first and second shaft parts 201, 301 can be disconnected after they have been connected (and subsequently re-connected). When the first and second shaft parts 201, 301 are connected, in the event that the first shaft part 201 is rotated, for example by an actuator, the second shaft part 301 corotates with the first shaft part 201. The first shaft part 201 comprises a proximal end 200 and a distal end 202. The proximal end 200 is operatively connectable to an actuator. They are operatively connectable in the sense that an output from the actuator causes rotation of the first shaft part 201. The actuator may be a rotary actuator, or a linear actuator. If the actuator is a linear actuator, a mechanical device may be present between the shaft 250 and the linear actuator to convert the linear motion of the actuator into rotary motion, in order to rotate the first shaft part 201. The first shaft part 201 may be directly connectable to the second shaft part 301, as shown in FIGs2A, 2Band2C. The firstand second shaft parts 201,301 may be directly connectable via a male-female connection. As best seen in FIG. 2B, in the illustrated example, the distal end 202 of the first shaft part 201 is arranged to enter a recess 302 in the second shaft part 301 such that the distal end 202 provides the male part and the recess 302 provides the female part, but in other examples it could be the other way around. The recess 302 is located at a proximal end 300 of the second shaft part 301. In the illustrated example, the distal end 202 has a flat head and the recess 302 is a linear recess for receiving the flat head, but it is contemplated that in other examples, the shape of the distal end 202 and / or the recess 302 could be different. For instance, the recess 302 could be cross-shaped, or both the distal end 202 and the recess 302 could be cross-shaped. Provided that the first and second shaft parts 201, 301 connect in a manner that causes them to co-rotate, the exact nature of the connection does not necessarily matter. The first shaft part 201 comprises a ledge 203 on which the washer 112 may be located. In the illustrated example, the ledge 203 is a circumferential ledge that is located around a curved outer surface of the first shaft part 201. When the washer 112 is located on the ledge 203, the washer 112 is positioned outside the chamber 115 of the housing defined by the first and second housing portions 101, 151. The first shaft part 201 comprises a recess 204. In the illustrated example, the recess 204 is a circumferential recess that is located around a curved outer surface of the first shaft part 201. The recess 204 is located above the ledge 203, and between the ledge 203 and the distal end 202 of the first shaft part 201. The second shaft part 301 comprises a proximal end 300 and a distal end 303. The distal end 303 may be connectable to the rotatable indicator 401. The distal end 303 may be fixed to the rotatable indicator 401, such that the rotatable indicator 401 co rotates with the second shaft part 301 when the second shaft part 301 is rotated. The rotatable indicator 401 may comprise a recess for receiving the distal end 303 of the second shaft part 301. In some examples, the distal end 303 of the second shaft part 301 has a flat head and the recess of the rotatable indicator 401 is a linear recess for receiving the flat head, but it is contemplated that in other examples, the shape of the distal end 303 and / or the recess could be different. For instance, the recess could be cross-shaped, or both the distal end 303 and the recess could be cross-shaped. Provided second shaft part 301 and the rotatable indicator 401 connect in a manner that causes them to co-rotate, the exact nature of the connection does not necessarily matter. The second shaft part 301 comprises one or more recesses 304, 305 for receiving the one or more seals / friction devices 160, 162. In the illustrated example, multiple recesses 304,305 are provided and each recess 304, 305 is for receiving a seal / friction device 160, 162, but in other examples only a single recess might be provided in the second shaft part 301 for receiving a single seal / friction device. The illustrated second shaft part 301 comprises a flange 306. In this example, the flange 306 is located at the proximal end 300 of the second shaft part 301. In other examples, the flange 306 could be located at the distal end 303 of the second shaft part 301. It can be seen in FIG. 2B that the flange 306 extends outwardly, in a radial direction, at substantially the same axial location along the second shaft part 301 at which the recess 302 is located to receive the distal end 202 of the first shaft part 201. The flange 306 extends outwardly, in a radial direction, further than the first shaft part 201 extends in the same direction when the first and second shaft parts 201, 301 are connected together. The flange 306 is arranged to support a first one 160 of the friction devices 160, 162. A first one 304 of the recesses 304, 305 is arranged to receive the first friction device 160 and is located in the flange 306. The first friction device 160 may be seated in the first recess 304. The first recess 304 extends around a curved outer surface of the second shaft part 301. In the illustrated example, the first recess 304 is located in a substantially planar surface of the flange 306. The substantially planar surface is an upper surface of the flange 306. The first friction device 160 may be located partially in the first recess 304, such that part of the first friction device 160 is located in the first recess 304 and part of the first friction device 160 protrudes beyond the first recess 304. A second one 305 of the recesses 304, 305 for receiving a second one 162 of the friction devices 160,162 is located around the curved outer surface of the second shaft part 301. The second recess 305 is spaced axially from the first recess 304. That is, the second recess 305 is spaced from the first recess 304 along an axis of rotation of the shaft 250. The second friction device 162 may be seated in the second recess 305. The second recess 305 extends around a curved outer surface of the second shaft part 301. The second recess 305 is a circumferential recess and is located in the curved outer surface of the second shaft part 301. The second friction device 162 may be located partially in the second recess 305, such that part of the second friction device 162 is located in the second recess 305 and part of the second friction device 162 protrudes beyond the second recess 305. In this regard, the second friction device 162 can be considered to extend around the second shaft part 201. FIGs.3A and 3B illustrate upper and lower perspective views of the first housing portion 101 connected to the first shaft part 201. It can be seen in FIGs3A and 3B that the first shaft part 201 is located partially in the aperture 102 in the first housing portion 101 and extends into the chamber 115 that is partially defined by the first housing portion 101. FIG. 3A shows the retainer 114 located around the first shaft part 201 and above the aperture 102 in the first housing portion 101, such that the retainer 114 is located inside the chamber 115. FIG. 3B shows the underside of the first housing portion 101, and the washer 112 located underneath the first housing portion 101 (and outside the chamber 115). The first shaft part 201 is located partially in the chamber 115, partially in the aperture 102, and partially outside the chamber 115. As shown in FIG. 3B, the aperture 102 in the first housing portion 101 is provided in a boss that protrudes from an underside of the first housing portion 101. FIGs 4A and 4B illustrate upper and lower perspective views of the second housing portion 151 connected to the second shaft part 301. It can be seen in FIGS 3A and 3B that the second shaft part 301 extends into the chamber 115. The inner surface of the upper wall 153 partially defines the chamber 115, and the second shaft part 301 extends beyond that inner surface into the chamber 115. The second shaft part 301 is partially located outside the chamber 115, partially located in the aperture 152, and partially located inside the chamber 115. The distal end 303 of the second shaft part 301 is located outside the chamber 115 and the proximal end 300 is located inside the chamber 115. The flange 306, which is located at the proximal end 300 of the second shaft part 301, is located inside the chamber 115. The flange 306 is located adjacent the inner surface of the upper wall 153 of the second housing portion 151. An advantage of the proximal end 300 of the second shaft part 301 being located in the chamber 115 is that it enables a user to use her fingers to rotate the second shaft part 301 into a position at which the second shaft part 301 is connectable to the first shaft part 201. For example, if the distal end 202 of the first shaft part 201 has a flat head and the proximal end 300 of the second shaft part 301 has a correspondingly shaped recess 302, the flat head and the recess 302 can be lined up such that the flat head can be received in the recess 302. FIG. 5A illustrates a plan view of an example of the switch box 1000. FIG. 5B illustrates a cross-section of the switch box 1000 shown in FIG. 5A, taken through the line marked C-C in FIG. 5A. Some of the reference numerals from previous FIGs have been omitted from FIG. 5B to aid clarity. The switch box 1000 may further comprise at least one bushing 501, 502. In the illustrated example, a first bushing 501 and a second busing 502 are provided. The first bushing 501 may be at least partially located in the aperture 102 in the first housing portion 101. In the illustrated example, the first bushing 501 is wholly located within the aperture 102, but this need not necessarily be the case in other examples. The first bushing 501 may be shaped as a hollow cylinder. The first shaft part 201 is partially located in the first bushing 501 and is arranged to rotate within the first bushing 501. The first bushing 501 may be impregnated with oil to reduce friction between the first shaft part 201 when the first shaft part 201 rotates relative to the first bushing 501. In some examples, the first bushing 501 is substantially formed from at least one metal, for instance, an alloy such as brass. The seal 113 is located at least partially within the aperture 102 and at least partially within the bushing 501. In the illustrated example, the seal 113 is located wholly within the aperture 102 and wholly within the bushing 501. The second bushing 502 may be at least partially located in the aperture 152 in the second housing portion 151. In the illustrated example, the second bushing 502 is wholly located within the aperture 152, but this need not necessarily be the case in other examples. The second bushing 502 may be shaped as a hollow cylinder. The second shaft part 301 is partially located in the second bushing 502 and extends beyond the second bushing 502 into the chamber 115. The second bushing 502 is arranged to rotate within the second bushing 502. The second bushing 502 may be impregnated with oil to reduce friction between the second shaft part 301 when the second shaft part 301 rotates relative to the second bushing 502. In some examples, the second bushing 502 is substantially formed from at least one metal, for instance, an alloy such as brass. FIG. 5B shows the shaft 250 extending through the chamber 115 defined by the housing 100 formed from first and second housing portions 101, 151. In this example, the distal end 202 of the first shaft part 201 extends into the recess 302 at the proximal end 300 of the second shaft part 301, such that both the first shaft part 201 and the second shaft part 301 are located in the aperture 152 in the second housing portion 151. Furthermore, both the first shaft part 201 and the second shaft part 301 are partially located inside the second bushing 502. The flange 306 is located outside the aperture 152 in the second housing portion 151 and the second bushing 502. In the illustrated example, the flange 306 is located wholly outside the aperture 152 and the second bushing 502 such that no part of the flange 306 is inside the aperture 152 or the second bushing 502. It was explained above that the switch box 1000 comprises one or more seals / friction devices 160, 162. The seals / friction devices 160, 162 may perform two main functions. As explained above, they may mitigate or prevent the ingress of fluids (e.g., flammable gases) into the chamber 115. They may resist the rotation of the rotatable indicator 401 and the second shaft part 301, when the second shaft part 301 is disconnected from the first shaft part 201. This is explained in further detail below. Each of the seals / friction devices 160, 162 may be located around and in contact with the second shaft part 301. It can be seen in FIG. 5B that the second seal / friction device 162 is located at least partially within the aperture 152 in the second housing portion 151. The second seal / friction device 162 is also located within the second bushing 502. The second seal / friction device 162 is arranged to contact the second shaft part 301 and the second bushing 502. More specifically, in the illustrated example, the second seal / friction device 162 is arranged to contact a curved outer surface of the second shaft part 301 and a curved inner surface of the second bushing 502. The contact that the second seal / friction device 162 makes with the second shaft part 301 and the second bushing 502 creates a seal between the two to mitigate or prevent the ingress of dust or fluids (e.g., water) into the chamber 115. Furthermore, when the second shaft part 301 is rotated, that contact creates friction which resists the rotation of the second shaft part 301 within the second bushing 502. The first seal / friction device 160 is located at least partially outside the aperture 152 of the second housing portion 151, and at least partially outside the second bushing 502. It can be seen in FIG. 5B that the first seal / friction device 160 is located wholly outside the aperture 152 of the second housing portion 151, and wholly outside the second bushing 502. The first seal / friction device 162 is arranged to contact the second bushing 502 outside the aperture 152 of the second housing portion 151. The first seal / friction device 162 is arranged to contact a (substantially flat) surface of the second bushing 502. That surface provides a portion of the ceiling of the chamber 115 in the illustrated example. The presence of two seals 160,162 provides the switch box 1000 and its contents with added protection against water or dust ingress. When the second housing portion 151 is disconnected from the first housing portion 101 (e.g., prior to initial installation, or following installation for maintenance purposes), the second shaft part 301 is disconnected from the first shaft part 201. Some prior switch boxes include a single shaft that extends through an aperture in a lower housing portion, through a chamber, through an aperture in an upper housing portion, and then shaft connects directly to the rotatable indicator. In such prior switch boxes, when the housing portions are disconnected, the rotatable indicator is free to rotate, and connecting the shaft to the rotatable indicator can be difficult. In contrast, in embodiments of the invention, the friction provided by the seals / frictions devices 160, 162 resists the rotation of the rotatable indicator 401 (and the second shaft part 301), such that after the firstand second housing portions 101, 151 have been disconnected and the first and second shaft parts 201, 301 are disconnected, there may be little to no rotation of the second shaft part 301 and the rotatable indicator 401. This may enable the first and second shaft parts 201, 301 to be easily connected together when the first and second housing portions 101, 151 are re-connected. It was explained above that the housing 100 may house one or more sensors / switches that are configured to sense a state of opening of a valve (e.g., whether the valve is in an open state, a partially open state or a closed state). The shaft 250 may be operatively connected to an actuator for transitioning the valve between its open state and its closed state. Each switch may provide an output that is indicative of a state of opening of the valve, such as the valve being in an open state, a partially open state, or a closed state. The output provided by the switch may be an electrical output. In some embodiments, each switch is a magnetic proximity switch that provides an output which is configured to change in dependence on the presence of a target. The target may be at least partially formed from a ferrous material. Each target may include a permanent magnet. A further example of the switch box 1000 will now be described in which one or more magnetic proximity switches may be located in the chamber 115 for sensing a state of opening of a valve. This further example of the switch box 1000 may include all of the features as the example described above in relation to FIGs 1A to 5B, along with some additional features relating to targets for actuating magnetic proximity switches. FIG. 6A illustrates an exploded view of the shaft 250 and a target carrier 400 according to the further example. FIG. 6B illustrates a cross section of the shaft 250 and the target carrier 400 through the line A-A shown in FIG. 6C. FIG. 6C illustrates a front elevation of the shaft 250 and the target carrier 400. When comparing FIGs 6A to 6C with FIGs 2A to 2C, it can be seen that FIGs 6A to 6C illustrate the additional features of a target carrier 400, one or more targets 450, target carrier retainer 420, a target carrier spring 430 and a support 470. The target carrier 400 is locatable in the chamber 115 and comprises an aperture 401. The shaft 250 may extend through the aperture 401, as shown in FIGs 6B and 6C. The target carrier 400 is arranged to at least one target 450 for causing actuation of one or more switches / sensors housed in the chamber 115. Each target 450 may be at least partially formed from a ferrous material. Each target 450 may include a permanent magnet. The target carrier 400 may include at least one through hole 402 for use in carrying a target 450. In the illustrated example, the target carrier 400 includes multiple through holes 402. Each through hole 402 may be arcuate in shape, as shown. Each target 450 may be mounted to the target carrier 400 using at least one fastener 452. Each target 450 may face downwardly, as illustrated in the FIGs. It will be appreciated by those skilled in the art that the targets 450 could be mounted to the target carrier 400 in ways that differ from that illustrated. The support 470 is for supporting the target carrier 400 in the chamber 115. The target carrier 400 may be locatable on the support 470. The support 470 may be supported by (e.g., mounted to) the shaft 250. For instance, the support 470 may be supported by (e.g., mounted to) the first shaft part 201. The support 470 may be fixed to the shaft 250 (e.g., the first shaft part 201), such that the support 470 rotates with the shaft 250. The shaft 250 may include one or more apertures for receiving the support 470. The support 470 may extend through such an aperture, such that a portion of the support is present either side of the shaft 250. In the illustrated example, the support 470 has the form of a support pin. An underside of the target carrier 400 may comprise a recess for receiving the support 470. That is, the target carrier 400 may be seated on the support 470 such that at least part of the support 470 is located at least partially in the recess. In some examples, the recess may enable the target carrier 400 to be rotated around the shaft 250 and seated on the support 470 in different rotational orientations. For instance, the underside of the target carrier 400 may include a cross-shaped recess that the target carrier 400 to be seated on the support pin 470 in two different orientations. The ability to rotate the target carrier 400 around the shaft 250 may enable targets 450 carried by the target carrier 400 to be more appropriately positioned relative to switches located in the chamber 115. The target carrier retainer 420 may be a circlip. The target carrier retainer 420 may have a larger diameter than the aperture 401 in the target carrier 400 through which the shaft 250 extends. The target carrier spring 430 may be a helical spring. The target carrier spring 430 may be located around the shaft 250, such as around the first shaft part 201. The target carrier retainer 420 may be located around the shaft 250, such as around the first shaft part 201. The target carrier spring 430 may be located between the target carrier retainer 420 and at least a portion of the target carrier 400. The target carrier spring 430 may abut the target carrier retainer 420 and the target carrier 400. The target carrier spring 430 may urge the target carrier 400 towards the support 470 (and away from the target carrier retainer 420). When a user (e.g. a technician) is, for example, setting up the switch box, while the first and second housing portions 101,151 are disconnected if the user wishes to rotate the target carrier 400 around the shaft 250 to align a particular target 450 with a particular switch 600, a force is applied to the target carrier 400 by the user that is directed away from the support 470 and towards the target carrier retainer 420 (in use, this is an upwards force). This force compresses the target carrier spring 430. The user may then rotate the target carrier 400 (while applying the upwards force) until it reaches the location in which the support 470 aligns with a recess at the underside of the target carrier 400, at which location the user ceases to apply the upwards force and then the target carrier spring 430 urges the target carrier 400 towards the support 470 such that the support 470 is located at least partially in the recess. FIG. 7A illustrates a plan view of a further example of the switch box 1000. FIG. 7B illustrates a cross-section of the switch box shown in FIG. 7A, taken through the line marked D-D in FIG. 7A. FIG. 7C illustrates a magnified portion of the cross-section of the switch box shown in FIG. 7B. The portion that is magnified is marked with the reference numeral 500 in FIG. 7B. FIGs 7B and 7C illustrates one or more switches 600 located in the chamber 115 (e.g., using some of the mounting locations 110). Each switch 600 may be actuated when a target 450, that is associated with the switch 600, is aligned with that switch 600. A target 450 may be considered to be aligned with a switch 600 when the target 450 is located directly above the switch / sensor 600. When an actuator causes a valve to move between a fully open state, a partially open state and / or a closed state, the actuator causes the shaft 250 to rotate, which changes the position of the targets 450 within the chamber 115. When the valve is in a closed state, the targets 450 are located relative to one or more switches 600 in the chamber 115 such that the output of the one or more switches 600 is indicative of the valve being in its closed state. When the actuator causes the valve to transition from the closed state to a partially open state or a fully open state, the actuator causes the shaft 250 to rotate, which causes the targets 450 to rotate around the shaft 250 (because the targets are fixed in position relative to the shaft 250) and, following the rotation, the targets 450 are located relative to one or more switches 600 in the chamber 115 such that the output of the one or more switches 600 is indicative of the valve being in its open state. In use, the switch box 1000 may be subject to external forces, such as vibratory forces. If such forces were to change the positioning of the target 450 relative to its associated switch 600, the target 450 might not be positioned correctly to cause actuation of its associated switch 600 when it is supposed to do so. When the first and second shaft parts 201, 301 are connected, the flange 306 of the shaft 250 is configured to resist movement of the target carrier 400 away from the support 470 when the first and second shaft parts 201, 301 are connected together and the shaft 250 extends through the target carrier 400, as shown in FIGs 7B and 7C. That is, the flange 306 is configured to resist movement of the target carrier 400 in a direction that is aligned with the axis of rotation of the shaft 250 and away from the support 470. This may prevent the targets 450 mounted on the target carrier 400 from becoming misaligned with the switches 600 in response to external forces, such as vibratory forces, being applied to the switch box 1000. In the illustrated example, the target carrier 400 is configured to abut the flange 306. That is, at least a portion of an upper surface of the target carrier 400 is configured to abut at least a portion of an underside surface of the flange 306. As shown in FIGSs 7B and 7C, in a dimension aligned with the axis of rotation of the shaft 250, the flange 306 is located between the upper wall 153 of the second housing portion 151 and the target carrier 400. The flange 306 is located between the aperture 152 in the upper wall 153 and the target carrier 400. Given that the second bushing 502 is located in the aperture 152, the flange 306 is located between the second bushing 502 and the target carrier 400. The flange 306 may also increase the provide the “flame path” that is associated with the aperture 152. The “flame path” associated with the aperture 152 is a path from the chamber 115, through the aperture 152 and out of the switch box 1000. The presence of the flange 306 extends the flame path (relative to if the flange 306 were not present), thereby increasing the probability that any flame that were to occur inside the switch box 1000 would not escape the switch box 1000. This enhances the safety of the switch box 1000. It was explained above that the flange 306 could be located at the distal end 303 of the second shaft part 301. In this regard, the flange 306 may be located outside the aperture, such as above the second bushing 502. In such examples, the flange 306 may be configured to support a friction device 160, such as within a recess located in the flange 306. That friction device may be seated in the recess, such that the friction device is located (at least partially) outside the aperture 152 of the second housing portion 151, and (at least partially) outside the second bushing 502. The friction device may be arranged to contact the second bushing 502 outside the aperture 152 of the second housing portion 151. The friction device may be arranged to contact a (substantially flat) surface of the second bushing 502. Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described. 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 description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e., to provide direct or indirect connection / coupling. In this 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 ‘can’ 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’, ‘can’, 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 includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example. Although examples 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 claims. Features described in the preceding description may be used in combinations other than the combinations explicitly described above. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. The description of a feature, such as an apparatus or a component of an apparatus, configured to perform a function, or for performing a function, should additionally be considered to also disclose a method of performing that function. For example, description of an apparatus configured to perform one or more actions, or for performing one or more actions, should additionally be considered to disclose a method of performing those one or more actions with or without the apparatus. Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not. The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning. The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that 28 perform substantially the same function, in substantially the same way to achieve substantially the same result. In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described. The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure. Whilst endeavouring in the foregoing specification to draw attention to those features believed to be of importance the applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon.

Claims

1. A switch box, comprising:a housing comprising at least a first housing portion and a second housing portion, the first and second housing portions being connectable to define a chamber for housing one or more switches, wherein:the first housing portion comprises an aperture; andthe second housing portion comprises an aperture;a first shaft part, located at least partially in the aperture in the first housing portion and extending into the chamber, operatively connectable to an actuator for rotating first shaft part;a second shaft part located at least partially in the aperture in the second housing portion and is removably connectable to the first shaft part such that the first and second shaft parts corotate when the first shaft part is rotated;a rotatable indicator, arranged to visually indicate a state of opening of a valve, connectable to the second shaft part such that the rotatable indicator corotates with the second shaft part, and such that the rotatable indicator rotates with the first shaft part when the first and second shaft parts are connected; andone or more friction devices for resisting the rotation the second shaft part, when the second shaft part is disconnected from the first shaft part.

2. The switch box of claim 1, wherein at least one friction device of the one or more friction devices is arranged to contact the second shaft part when the second shaft part is rotated.

3. The switch box of claim 2, wherein the second housing portion comprises a bushing, the second shaft part is partially located within the bushing and is arranged to rotate within the bushing, and the at least one friction device is arranged to contact the bushing when the second shaft part is rotated.

4. The switch box of claim 3, wherein the bushing is at least partially located within the aperture of the second housing portion.

5. The switch box of any of claims 2,3 or 4, wherein the at least one friction device is located at least partially within the aperture of the second housing portion.

6. The switch box of any of claim 3 or 4, or claim 5 when dependent on claim 3 or 4, wherein the at least one friction device is located within the bushing.

7. The switch box of any of claims 2 to 6, wherein the second shaft part comprises a curved outer surface, and at least one of the friction devices is arranged to contact the curved outer surface of the second shaft part when the second shaft part is rotated.

8. The switch box of claim 3, 4 or 6, or claim 5 or 7 when dependent on claim 3 or 4, wherein the bushing has a curved inner surface, and the at least one friction device is arranged to contact the curved inner surface when the second shaft part is rotated.

9. The switch box of any of any of claims 5 to 8, wherein the at least one friction device is located around the second shaft part.

10. The switch box of any of claims 5 to 9, wherein the second shaft part comprises a recess, and the at least one friction device is located in the recess.

11. The switch box of claim 10, wherein the recess is a circumferential recess in a curved outer surface of the second shaft part.

12. The switch box of any of claims 5 to 11, wherein the at least one friction device is ring-shaped.

13. The switch box of claim 2, 3 or 4, wherein the at least one friction device is located at least partially outside the aperture of the second housing portion.

14. The switch box of claim 3 or 4, or claim 13 when dependent on claim 3 or 4, wherein the at least one friction device is located at least partially outside the bushing.

15. The switch box of claim 13 or claim 14 when dependent on claim 13, wherein the one friction device is arranged to contact the bushing outside the aperture of the second housing portion.

16. The switch box of claim 2, 3, 4, 13, 14 or 15, wherein the second shaft part comprises a recess, and the at least one friction device is located in the recess.

17. The switch box of claim 16, wherein the second shaft part comprises a flange, and the recess is located in the flange.

18. The switch box of claim 17, wherein the recess is located in a substantially planar surface of the flange.

19. The switch box of claim 13 to 18, wherein the at least one friction device is ringshaped.

20. The switch box of any of the preceding claims, wherein the one or more friction devices are formed from at least one resilient material.

21. The switch box of claim 20, wherein the at least one resilient material comprises at least one polymer.

22. The switch box of any of the preceding claims, wherein the second shaft part is directly connectable to the first shaft part.

23. The switch box of claim 22, wherein the second shaft part is directly connectable to the first shaft part by a male-female connection.

24. The switch box of any of the preceding claims, wherein the second shaft part is fixedly connected to the rotatable indicator, such that the rotatable indicator corotates with the second shaft part.

25. The switch box of any of the preceding claims, wherein when the rotatable indicator is connected to the second shaft part, and the second shaft part is connectedto the first shaft part, the rotatable indicator, the second shaft part and the first shaft part are arranged to rotate about the same axis of rotation.5

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