TIMEPIECE COMPRISING A BAROMETRIC PRESSURE SENSOR

Technical Field

[0001] The present invention relates to the field of timepieces. In particular, it relates to timepieces comprising a barometric pressure sensor.

State of the art

[0002] Many different timepieces are known from the state-of-the-art which incorporate a barometric pressure sensor for indicating atmospheric pressure and/or altitude. For example, DE 68038, DE 63878, CH 376438, CH 324756, CH 433127, WO 13079810, US 2716327, CH 696047, FR 2209093, CH 4225, CH 328502, and CH 1425161 describe various constructions of timepieces integrating barometric pressure sensors, conventionally in the form of an aneroid capsule. In each of these constructions, the pressure sensor and its indicator are integrated to varying degrees with the timepiece movement. For instance, in CH 4225, amongst others, the indicator hand for the pressure sensor is coaxial with the time indicating hands and indicates on its own scale on the same dial. This requires a significant amount of integration of both the time measurement and the pressure measurement systems on the watch, leading to complexities in construction and difficulty in maintenance or replacement of one or the other subsystems.

[0003] An attempt at a more modular construction of such a timepiece is disclosed in CH 696047. In this timepiece, an arbor mounted in the encasement ring transmits movement from the pressure sensor, around the timepiece movement, to an indicator mounted conventionally and coaxially with the time indicating hands. Although this arrangement permits the use of a standard movement, the transmission of movement around the timepiece movement adds a degree of complexity and complicates assembly of the timepiece.

[0004] An object of the invention is thus to overcome at least partially some of the above-mentioned drawbacks of the prior art, thereby proposing a fully modular timepiece of simple construction and ease of assembly. Disclosure of the invention

[0005] More specifically, the invention relates to a timepiece comprising a housing comprising a middle, the housing being closed on a first side by a glass and on a second side by a case back, a timepiece movement arranged in the housing, said movement preferably being a self-winding mechanical movement although this does not necessarily have to be the case, time indicator organs cinematically linked to the movement and situated between the movement and the glass, a barometric pressure sensor situated between the movement and the case back, and a pressure indicator cinematically linked to the atmospheric pressure sensor.

[0006] According to the invention, the barometric pressure sensor is arranged substantially coaxial to the movement, and the pressure indicator is situated nearer to the case back than at least part of the movement, wherein at least part of the pressure indicator is visible through the glass around the periphery of movement, i.e. is visible between the movement and the middle.

[0007] In consequence, a completely modular timepiece construction is proposed which can utilise standard movements and standard pressure sensors. Since the movement and the pressure sensor can be rendered independent by this construction, fabrication, assembly, maintenance, and replacement of parts is significantly simplified compared to prior art constructions.

[0008] Advantageously, the movement is supported in the housing by an encasement ring situated between the movement and the middle, the encasement ring being at least partially transparent. The encasement ring may for instance be made at least partially (i.e. partially or completely) of transparent material (e.g. glass, plexiglass, sapphire), or may simply be partially transparent by virtue of comprising at least one opening in an otherwise opaque encasement ring, e.g. made of metal, carbon fibre or similar. This opening may, for instance, be at least one circumferential slot. The pressure indicator is thus at least partially visible through the encasement ring. [0009] Advantageously, the glass and the case back are hermetically sealed to the middle by means of gaskets, and a vent tube is provided in the middle linking the interior of the housing to the outside. The vent tube comprises a semipermeable membrane permitting the passage of air through the vent tube but blocking the passage of water therethrough. In consequence, the pressure sensor can be exposed to ambient air pressure without risk of moisture, dust etc. penetrating into the inside of the casing.

[0010] Advantageously, a hollow crown is arranged surrounding an outer end of the vent tube, said crown comprising a sealing arrangement arranged so as to permit selective hermetic sealing of the vent tube. The casing can thus be entirely hermetically sealed by the user to improve the watertightness of the timepiece, for instance in the case in which the timepiece is likely to be submerged in water. The vent tube may be hermetically sealed e.g. by screwing the crown onto the middle either directly or via a pipe fixed on the middle, said pipe comprising a first seal arranged to seal the vent tube to the pipe, said crown comprising a second seal arranged to seal the crown to the pipe.

[001 1] Alternatively, the glass and the case back are hermetically sealed to the middle by means of gaskets, and at least one opening is provided in the middle. This at least one opening is closed by a semipermeable membrane permitting the passage of air through the opening but blocking the passage of water through the opening.

[0012] Advantageously, a hollow crown is arranged surrounding an outer end of a stem which passes through a pipe provided in the middle in the conventional fashion, proximate to the semipermeable membrane. At least one of the middle and the crown comprises a sealing arrangement arranged so as to permit selective hermetic sealing of the opening. As above, the casing can thus be entirely hermetically sealed by the user to improve the watertightness of the timepiece, for instance in the case in which the timepiece is likely to be submerged in water. This sealing may be achieved by the pipe comprising a first seal arranged to seal the stem to the pipe, and by the middle comprising a second seal arranged in an annular groove provided therein. This second seal is arranged to selectively seal the crown to the middle in such a manner as to prevent water from reaching the semipermeable membrane.

[0013] Advantageously, the pressure indicator comprises a hand at least partially made of carbon fibre, preferably comprising a strand of carbon fibre. For instance, the hand can be made of a single strand of carbon fibre. By using such materials, the pressure indicator is rendered as light as possible, thereby reducing its inertia and reducing friction. The pressure indication is thereby made more responsive to changes in ambient pressure, rendering the pressure indication more accurate.

[0014] Advantageously, an adjustable scale ring is provided, the adjustable scale ring being rotatable with respect to the middle. In consequence, a scale provided on the adjustable scale ring can be calibrated to ambient conditions by the user with respect to e.g. a fixed scale provided on a fixed scale ring. The adjustable scale ring is advantageously attached to the barometric pressure sensor such that the barometric pressure sensor rotates therewith, for instance if the case in which the adjustable scale ring is calibrated to the barometric pressure sensor at the point of manufacture. The barometric pressure sensor and said adjustable scale ring may be mounted to a rotatable annular ring, said annular ring being arranged so as to be rotated by a user. The annular ring is advantageously sandwiched between at least part of the barometric pressure sensor and the adjustable scale ring. In consequence, the components in question are mounted in the timepiece as a single, simple unit.

[0015] Advantageously, the annular ring is selectively cinematically linked to the crown such that rotation of the crown causes rotation of the annular ring in at least one axial position of the crown, e.g. its fully pulled out position. In consequence, the user can easily adjust the adjustable scale ring.

[0016] Advantageously, a plurality of stable axial positions of the crown is defined by a plate spring translationally engaged with the vent tube and interacting with a plurality of notches provided in the middle. An extremely simple positioning of the crown is thereby attained. [0017] Advantageously, the annular ring comprises contrate gearing, said contrate gearing being positioned by at least one jumper spring. The contrate gearing may extend towards the encasement ring, whereupon the at least one jumper spring is mounted such that it extends towards said contrate gearing. The system for positioning the annular ring is thus extremely compact and simple.

[0018] Advantageously, the at least one jumper spring is arranged to urge the annular ring onto a corresponding shoulder provided on the case back. The annular ring and the other components attached thereto can thus be supported in the housing by only the shoulder and the jumper springs, obviating any requirement for further fixation means.

[0019] Advantageously, the adjustable scale ring comprises a scale indicating pressure, and wherein a fixed scale ring is arranged on the middle, said fixed scale ring comprising a scale indicating altitude. In consequence, both altitude and pressure can be indicated.

Brief description of the drawings

[0020] Further details of the invention will now be described with respect to the figures, in which:

- Figure 1 illustrates an exploded view of a timepiece according to the invention;

- Figure 2 illustrates a cross-sectional view of a timepiece according to the invention;

- Figure 3 illustrates a perspective view of the relationship between the movement, the encasement ring, and the annular ring, and the crowns, isolated from other components of the timepiece according to the invention;

- Figure 4 illustrates a perspective view of the relationship between the pressure sensor, the annular ring, and the calibration crown, isolated from other components of the timepiece according to the invention;

- Figure 5 illustrates a perspective view of the system for positioning the calibration crown; - Figure 6 illustrates a front view of a timepiece according to the invention as seen by a user;

- Figure 7 illustrates an exploded view of a further variant of a venting crown;

- Figure 8 illustrates a cross-sectional view of a timepiece incorporating the crown of figure 7.

Embodiments of the invention

[0021] In the following specification, the terms "upper" and "above" indicate directions towards the glass 45; the terms "lower" and" below" indicate directions towards the case back 9. Figure 1 illustrates an exploded view of the construction of a timepiece 1 according to the invention. Figure 2 illustrates in cross-section the structure of the timepiece with calibration crown 29 in its innermost position, this cross-section being along a diameter of the watch passing along the axis of tube 31.

[0022] The timepiece 1 comprises a middle 3 in which is mounted a movement 5 by means of an encasement ring 7. As is conventional, movement 5 is surmounted by a dial 8 (clearly visible on figure 2). Middle 3 is closed on its bottom side by a case back 9, and on its front side by a glass 45 (not illustrated in figure 1 ; see figure 2) so as to form a housing. It should be noted that further conventional features such as horns for the attachment of a bracelet have not been illustrated. A fixed scale ring 2, with markings indicating altitude, is provided on the front side of middle 3, held in place by the glass 45, fixed scale ring 2 being held in sandwich between the glass 45 and a shoulder 51 of the middle 3. Fixed scale ring 2 may be located with pins or screws, or may be glued in place. Alternatively, a scale may be provided on a convenient surface of the middle 3.

[0023] Movement 5 can be of any convenient type, whether mechanical, electromechanical, or digital, and may be either automatic or manual winding in the case of a mechanical movement. As is conventional, time indicators e.g. hands 53 or discs are provided between the movement 5 and the glass 45. As the invention is practised today, the movement 5 is a mechanical automatic winding movement. Movement 5 comprises a conventional winding and/or setting stem 6 which passes through an opening (not visible in figure 1) in the middle 3 and terminates in a crown 4 as is conventional and need not be described further.

[0024] Encasement ring 7 is provided with openings 1 1 , visible to the user through the glass 45, which allow the user to view a pressure indicator, as will be described more clearly below. Openings 1 1 are illustrated here in the form of elongated circumferential slots, however other forms are naturally possible. It is equally possible that the movement 5 is held by the encasement ring 7 merely at a number of discrete points, openings 1 1 in this case being formed as cutaways between the movement 5 and the exterior of the encasement ring 7.

[0025] Alternatively, encasement ring 7 can be made partially or entirely of a transparent material such as glass, plexiglass, sapphire, or similar, with or without openings.

[0026] Encasement ring 7 is attached to the middle 3 by means of a plurality of screws 35, numbering here three, however any convenient number can be used, inserted from the lower side of encasement ring 7 and screwing into corresponding threaded holes (not illustrated) provided in the middle 3. Screws 35 also each support a jumper spring 37 on the lower side of encasement ring 7, the function of which will be made clear below.

[0027] Mounted beneath the movement 5 between the movement 5 and case back 9 and coaxially to the movement 5 is a barometric pressure sensor 13 of any convenient type, preferably a mechanical type comprising an aneroid capsule. Pressure sensor 13 is provided with an indicator hand 40, 41 (see figure 2), which extends underneath the movement 5 towards the periphery of the middle, and at least part of which is visible through the openings 1 1 as will appear more clearly below.

[0028] Advantageously, the pressure sensor 13 is mounted to an annular ring 15 which is rotatably mounted in the housing, by means of screws 19 which pass through corresponding holes 21 in annular ring 15 and screw into corresponding threaded holes (not visible) in an adjustable scale ring 23. Annular ring 15, adjustable scale ring 23, and pressure sensor 13 are mutually fixed together and thus rotate together. Adjustable scale ring 23 is situated on the upper side of annular ring 15 and carries a scale e.g. of atmospheric pressure measured in hPa/mbar, bar, or atmospheres, which is visible through openings 1 1 , or through the encasement ring 7 itself in the case in which this latter is constructed of fully transparent material, and over which at least part 41 of a pressure indicator 40, 41 passes so as to indicate the pressure inside the housing. As such, the scale provided on adjustable scale ring 23 is calibrated to the pressure sensor 13 and to the pressure indicator at the point of manufacture. Alternatively, adjustable scale ring 23 may be integrated with annular ring 15 as a single piece, the scale being printed directly on annular ring 15. It should be noted that pressure indicator 40 extends behind the movement 5 over the majority of its length, only its extremity being visible between the movement 5 and the middle 3 through the openings 1 1 in the encasement ring 7, or through the encasement ring 7 itself in the case in which this latter is constructed of fully transparent material.

[0029] Annular ring 15 comprises contrate gearing 25 located near the periphery of the annular ring 15 and extending in the direction of the encasement ring 7. Alternatively, any other convenient form of gearing can be used.

Furthermore, and visible on figure 2 only, annular ring 15 may comprise openings 26 to permit free passage of air through annular ring 15 to guarantee that no pressure gradient exists within the housing.

[0030] Annular ring 15 is supported on a shoulder 17 on the case back 9, and is urged against shoulder 17 by jumper springs 37 which act perpendicular to the plane of the annular ring 15 and apply a force in the direction of the case back. Jumper springs 37 also serve to position annular ring 15 so as to prevent undesired rotation thereof.

[0031] In consequence of this construction, removal of the pressure sensor 13 along with the adjustable scale ring 23 and the annular ring 15 can be carried out merely by unscrewing the case back 9 and then removing the assembly comprised of pressure sensor 13, adjustable scale ring 23 and annular ring 15 without removal of any further fixation means. The movement 5 can subsequently be removed together with the encasement ring 7 merely by unscrewing screws 35 to which the technician then has free access.

[0032] Contrate gearing 25 meshes selectively with a pinion 27 which is cinematically linked to calibration crown 29 via a hollow vent tube 31 slidably mounted in a pipe 33 which is hermetically attached to middle 3, so as to permit the user to be able to adjust the angular position of the adjustable scale ring 23. It should be noted that in Figure 2 the lower part of the calibration crown 29 situated below the horizontal chain line is illustrated in a different angular position that the upper part of the calibration crown 29 situated above the horizontal chain line.

[0033] Calibration crown 29 is rotationally fixed to vent tube 31 , and comprises an inner thread such that it can be screwed onto a corresponding outer thread provided on pipe 33. Furthermore, the outer end of vent tube 31 is closed by a semipermeable membrane 39, which permits air to penetrate through the membrane 39, but prevents ingress of water. Such semipermeable membranes are made for instance of expanded PTFE (ePTFE). Adjacent to semipermeable membrane 39 is provided a spacer 42 which serves to hold membrane 39 in place and also to ensure that when the crown is in the open position, sufficient space exists between the membrane 39 and the inside face of the crown 29 to permit the passage of air. Plate spring 43 serves to position vent tube 31 in a plurality of stable axial positions, as will be described in more detail below.

[0034] In the view of figure 2, calibration crown 29 is in its screwed-in position, ensuring that the housing is hermetically sealed. To this end, a first seal 61 is provided on pipe 33 between the pipe 33 and vent tube 31 , and a second seal 63 is provided on the calibration crown 29 between the pipe 33 and the calibration crown 29, arranged such that, when the calibration crown 29 is screwed onto pipe 33, the seals 61 , 63 are compressed.

[0035] To take a pressure and/or altitude reading, the calibration crown 29 is unscrewed from the pipe 33 withdrawn into its intermediate stable position (not illustrated). In this position, pinion 27 does not mesh with contrate gearing 25, and can freewheel. Second seal 63 is withdrawn with the calibration crown 29 and is no longer in contact with the pipe 33. In consequence, air can flow between the pipe 33 and the inner wall of the calibration crown 29, and into or out of vent tube 31 via membrane 39, thereby equalising the pressure between the inside of the housing and the atmosphere. Pressure sensor 13 is thus exposed to the ambient conditions and indicates the ambient atmospheric pressure on the adjustable scale ring 23, and the altitude on fixed scale ring 2, this latter assuming that the indicator has been correctly calibrated for variations in atmospheric pressure. Nevertheless, the inside of the housing is protected from ingress of water by semipermeable membrane 39, although membrane 39 cannot withstand a significant depth of water immersion.

[0036] To calibrate the altitude indication, the calibration crown 29 is withdrawn into its outermost stable position (not illustrated). In this position, pinion 27 meshes with the contrate gear 25 of the annular ring 15. Turning calibration crown 29 at this stage causes annular ring 15 to rotate about its axis, thereby rotating pressure sensor 13 and adjustable scale ring 23, together with pressure indicator 40, 41.

[0037] Hence, the user of the timepiece can adjust the position of the indicator 40 and its corresponding pointer 41 with respect to the altitude markings provided on fixed scale ring 2 so as to adjust for variations in atmospheric pressure. For instance, if the user knows his current altitude, he can withdraw calibration crown 29 into its outermost position and adjust the position of annular ring 15 until the indicator 41 points to the correct altitude. Once the user has completed these actions, he pushes the calibration crown 29 back into its intermediate position to allow the altitude and/or pressure measurement to continue in real-time. Alternatively, he can push the calibration crown 29 back to its innermost position and screws it back onto the case, re-establishing hermetic sealing of the housing.

[0038] It should furthermore be noted that, although calibration crown 29 and setting crown 4 are separate, distinct crowns in the present embodiment, it is also possible to integrate the calibration function with the setting and/or winding function such that a single crown performs all functions. This can be achieved e.g. by using vent tube 31 as a hollow setting and/or winding stem, or by arranging a further setting/winding stem passing along the centre of vent tube 31. Another option could be to split the combined functions of the calibration crown 29 into two distinct, separated crowns. One for ventilation, the other one for calibration.

[0039] Figure 3 illustrates in more detail the relationship between encasement ring 7, movement 5, annular ring 15 and crowns 4, 29. Other components of the timepiece, including the middle 3, the pressure sensor 13, and the adjustable scale ring 23, have been omitted in this figure for clarity.

[0040] Movement 5 is supported in the encasement ring 7 in the conventional fashion. Setting stem 6 is hidden from view by a solid portion 7a of encasement ring 7 situated between adjacent openings 1 1. As described above, screws 35 attach the encasement ring 7 to the middle 3, and also support jumper springs 37, one of which is visible in figure 3. The distal end of jumper spring 37 positions the annular ring 15 angularly by engaging between 2 adjacent teeth of the contrate gear 25. Since jumper springs 37 apply a force to the contrate gear 25 in the direction of the case back, they force the annular ring 15 down onto the shoulder 17 of the case back 9 (see figures 1 and 2), and thus hold it in position both axially and angularly.

[0041] Figure 4 illustrates more clearly the relationship between the pressure sensor 13, the annular ring 15, and several parts of the adjustment mechanism for the annular ring, here illustrated in its inactive position.

[0042] Pressure sensor 13 is mounted in annular ring 15 as described above. In this figure, pressure indicator 40, 41 is clearly visible. Pressure indicator 40, 41 comprises a hand 40 terminating in a pointer 41. In order to minimise the inertia of the pressure indicator 40, 41 , the hand 40 and/or the pointer 41 can be made out of carbon fibre. The hand, in particular, may comprise, or indeed may even consist of, a single filament of carbon fibre as narrow as possible while still retaining the required stiffness and other mechanical properties.

Hand 40 is bent lightly upwards such that pointer 41 indicates on the sloping surface of adjustable scale ring 23. In this figure, crown 29 and pinion 27 are illustrated in their inactive position, i.e. pushed into the middle as far as they will go. Pinion 27 does not mesh with the contrate gearing 25 of the annular ring 15 in this position, however withdrawing the crown to its outermost position causes the pinion 27 to engage with the contrate gearing 25 so as to enable the user to adjust the angular position of annular ring 15, pressure sensor 13, and adjustable scale ring 23 with respect to the other components of the timepiece.

[0043] Figure 5 illustrates the arrangement used in the present timepiece for positioning calibration crown 29. As can be seen in figure 1 , plate spring 43 comprises a lateral slot 44 which engages with the vent tube 31 so as to translate therewith. In the present example, plate spring 43 engages between the pinion 27 and a shoulder provided on the innermost end of vent tube 31 (see figure 2). Alternatively, lateral slot 44 could engage with an annular groove provided in that tube 31. Plate spring 43 is furthermore provided with lateral elastic wings 65 engaging with notches 67a, 67b, 67c provided in the middle 3 either side of the vent tube 31 so as to position calibration crown 29, vent tube 31 , and pinion 27 in each of its 3 stable positions. Should more stable positions be required, it is a simple matter to provide a greater number of notches in the middle 3.

[0044] Furthermore, plate spring 43 comprises a guide member 69 which bears on the underside of fixed scale ring 2 so as to maintain plate spring 43 in position.

[0045] Plate spring 43 has three stable positions namely innermost position 43a (illustrated in solid), middle position 43b (illustrated in dark "ghost" form), and outermost position 43c (illustrated in light "ghost" form). In each of these positions 43a, 43b, 43c, the vent tube 31 is maintained in the position by the engagement of lateral elastic wings 65 in the respective notches 67a, 67b, 67c.

[0046] Advantageously, to avoid fatiguing lateral elastic wings 65, when the crown 29 is fully screwed in, plate spring 43 is pushed further towards the centre of the middle such that lateral elastic wings 65 are not in contact with notch 67a, thus are not stressed. [0047] It goes without saying that this positioning arrangement for calibration crown 29 is perfectly suited to be used with a conventional setting and/or winding crown, and is not linnited to use with a vent tube. In the case of application of plate spring 43 to a conventional winding and/or setting crown combined with a stem, lateral slot 44 would engage with a groove provided on the stem, or would engage between a shoulder provided on the stem and e.g. a pinion provided on the stem.

[0048] Figure 6 illustrates a front view of a timepiece 1 according to the invention. In addition to many of the features already described above, which need not be described again, this figure clearly shows how the adjustable scale ring 23 and pointer 41 are visible through openings 1 1 in encasement ring 7, and how pointer 41 simultaneously indicates atmospheric pressure on adjustable scale ring 23 and altitude on fixed scale ring 2. Self-evidently, if the adjustable scale ring 23 is rotated by means of calibration crown 29, its scale markings move with respect to altitude markings on fixed scale ring 2.

Furthermore, it is clear from figure 6 that the setting stem 6 is rendered invisible to the user of the timepiece since it extends from movement 5 to crown 4 underneath a section 7a of encasement ring 7 situated between two adjacent openings 1 1.

[0049] Figures 7 and 8 illustrate a further variant of calibration crown 29, in exploded view and in cross-section in its screwed-in position respectively. The remaining features of the timepiece 1 are substantially unchanged, with the exception of the middle 3 in the immediate proximity of the calibration crown 29, and the details thereof need therefore not be repeated here. For instance, it should be noted that the plate spring 43 is applied in exactly the same manner to the embodiment of figures 7 and 8 as it is in figure 5.

[0050] In the variant of figures 7 and 8, vent tube 31 has been replaced with a stem 71 , upon one end of which is mounted pinion 27 by means of a screw 73. The opposite end of stem 71 is fixed in a recess on the inside of crown 29 as is conventional, e.g. by force-fitting, soldering, welding, brazing, gluing or similar. Stem 71 passes through pipe 33, which it fixed to the middle 3, in the conventional manner, and is sealed thereto by first seal 61. Since stem 71 is solid, passages 75 are provided through the middle 3 immediately adjacent to the pipe 33, to permit the passage of air. To prevent ingress of water, dust etc., passages 75 are closed by semipermeable membrane 39 of annular construction. Membrane 39 comprises an annular active membrane area 39a, through which air can pass but moisture and dust cannot, and is bonded by adhesive 77 to the middle 3 on an appropriately-arranged surface.

[0051] In the screwed-in position of the calibration crown 29, in which a male thread provided on pipe 33 interacts with a female thread provided on the inside of calibration crown 29, crown 29 is hermetically sealed to the middle 3 by means of second seal 63, which is situated in an annular groove 79 provided on the middle 3, and which contacts a bevelled surface 81 appropriately provided on calibration crown 29. Calibration crown 29 is thus hermetically sealed to the middle 3, and membrane 39 is not exposed to ambient conditions.

[0052] When the calibration crown 29 is unscrewed from pipe 33 and withdrawn into its intermediate position, second seal 63 no longer contacts bevelled surface 81 , and hence air can penetrate around the outside of calibration crown 29, and can enter the interior of the housing via the active membrane area 39a of membrane 39 and the passages 75, thereby equalising the pressure inside and outside the housing such that the barometric pressure sensor 13 can indicate the ambient pressure and/or altitude. As in the case of the embodiment of figures 1 -6, in this position pinion 27 does not mesh with the contrate gearing 25 of annular ring 15.

[0053] As in the case of the embodiment of figures 1 -6, when the calibration crown 29 is withdrawn into its outermost position, pinion 27 meshes with the contrate gearing 25 of annular ring 15, permitting annular ring 15 to be rotated by the user so as to calibrate the altitude indication.

[0054] As above, calibration crown 29 may naturally be arranged so as to perform conventional winding and setting functions, combining all these functions in a single crown. The required modifications to do this are clear to the skilled person. [0055] It should be noted that it is not essential that either of the venting crown systems described above, comprising respectively crown 29, vent tube 31 , and semipermeable membrane 39 (see figures 1 and 2), or crown 29, stem 71 , openings 75 and semipermeable membrane 39 (see figures 7 and 8), be used with the coaxial timepiece construction described above. They can self- evidently also be used in combination with any other arrangement of a pressure sensor in a watch housing, or even in a timepiece not incorporating a pressure sensor in the case in which a requirement arises in which it is advantageous to be able to equalise the pressure inside and outside of the watch case without permitting ingress of water. In other words, in its most generic form, the calibration crown system can be used in a timepiece comprising a housing formed of a middle closed on a first side by a glass and on a second side by a case back, the calibration crown system comprising a vent tube passing through the middle and comprising a semipermeable membrane, and a screwed crown which, when screwed down, is arranged so as to hermetically seal the vent tube. Naturally, other details as described above can be incorporated therein, such as the arrangement of the pipe 33, the spacer 42, the openings 75, and the seals 61 , 63 of both variants. In this case, the crown could be for instance a setting and/or winding crown, the vent tube performing the role of setting and/or winding stem.

[0056] Additionally, the arrangements described above for adjusting adjustable scale ring 23 can be applied to other timepieces comprising other arrangements of pressure sensor 13, and/or indication of measurements other than pressure/altitude, such as for instance temperature, humidity, time, and so on.