Portable electronic device comprising a pressure sensor

0001The present invention relates to a portable electronic device to the wrist, including a wristwatch diver, a depth gauge or an altimeter, having a housing and a pressure sensor which is mounted in a housing housing and has an exposed surface within the housing for receiving the ambient pressure, said recess opening on an outer face of the housing and being closed on this side by a cover having an outer wall provided with at least an orifice in front of the housing for transmitting the ambient pressure outside the housing to housing.

0002Discloses a wristwatch of this kind, described in EP 195 636, where the housing of the pressure sensor is provided in a protrusion side of the housing and opens onto the upper face of the housing so that can set up the sensor from above. According to a construction which is the most currently running, the pressure sensor comprises a piezoresistive element silicon which is accommodated in a cup-shaped structure and coated with a gel silicone so as to be protected from the effects of water. This gel is further coated with a flexible layer of silicone rubber or resin, which forms the exposed surface the sensor and transmits the ambient pressure piezo-resistive element. Above, the cover closing the housing is formed by a perforated circular plate. the orifices this plate are arranged along its periphery, so as not to be opposite the silicon element and the gel coating thereof. This provision aims to prevent foreign bodies engaging in these holes can damage the silicon element or gel.

0003However, such an arrangement has two disadvantages. On the one hand, requires enlarge the closure plate so that the orifices lie outside of the central area occupied by the sensor. On the other hand, it would be desirable to subtract the element silicon to prolonged exposure to sunlight, but the construction described above does not sufficiently stops diffusion of light in the sensor.

0004In EP 677 798 there is described a watch of the type indicated in the introduction above, but wherein the housing for the pressure sensor is formed by a tube placed in a cavity in the back of the watch case. To avoid supporting the housing against the wearer's wrist discomfort transmission ambient pressure to the sensor, the back of the case has grooves, while that the housing is covered by a lid or cap having an outside bearing surface located flush with the case back to lean against the wrist carrier and leave behind the cover or through the side openings a communication between the grooves and the sensor housing. Such a construction has the disadvantage of leading to a large thickness of the watch. On the other hand, it is not not arranged to prevent the sunlight from reaching the sensor, in particular when the watch is not put on the wrist.

Summary of the Invention

0005The present invention aims to remedy the aforementioned drawbacks of the prior art, thanks to a particularly simple and effective arrangement of organs Mounting the sensor in the housing intended for it. A particular purpose is to design these so as to simplify a large extent the organs mounting the sensor and components of the device associated to it, in particular for an automated mounting.

0006To this end, the invention relates to a portable electronic apparatus of the type indicated above, characterized in that said outer face of the housing from a side of the housing which is not in contact with the wearer's wrist and in that least one shield is disposed in the housing behind the orifice the hood so as to prevent any online communication between the right or cover ports and the exposed surface of the pressure sensor, so that any transmission path of the ambient pressure to the exposed surface of sensor is sinuous.

0007Thus, the protective screen provided in this invention has a dual protection of the sensor, that is to say against solid bodies and against the light, and this with a construction that can be extremely simple and compact by example with the addition of a plate having perforations judiciously arranged in the cover closing the housing of the pressure sensor. Furthermore, this Construction advantageously allows placement or the external openings of the hood before the exposed surface of the sensor, so in the central region of the hood, which reduces the outer dimensions and the visual impact of the cover. The side of housing including housing for the sensor can also be a side face that the upper side of the housing.

0008According to an embodiment very simple and inexpensive, especially if the cover is a plastic molded part, the shield can be formed by a perforated plate extending substantially parallel to said cover wall, the holes in the perforated plate being laterally offset with respect to each orifice of hood such that orthogonal projection of the orifice on the perforated plate is spaced holes thereof.

0009Other features and advantages of the invention will be better understood using the following description of a presently preferred embodiment, given by way of nonlimiting example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

0010<sl><li>Figure 1 is a side view of a wristwatch comprising a sensor pressure and arranged according to the principles of the present invention.</li><li>Figure 2 is an exploded perspective view of the pressure sensor and elements of its mounting in the case of the watch of Figure 1.</li><li>Figure 3 is a front view of the housing for the pressure sensor.</li><li>Figure 4 is a partial sectional view of the watch according to the line IV-IV of Figure 1.</li><li>Figure 5 is a perspective view of the rear face of a cap shown in Figure 2.</li><li>Figure 6 is a front view of a protective plate shown in 2.</li></sl>

detailed description of an embodiment of the invention

0011Referring to Figures 1 to 4, a wristwatch 1 has plunger a housing 2 of rigid synthetic material which contains in particular a movement electronic watch, a sensitive pressure sensor to the ambient pressure prevailing outside the housing, the analog display members and / or digital and electronic circuitry for processing the pressure data and display results by the display means. The housing 2 includes a middle part 3 in synthetic, surrounding a central cavity 4 (Figure 4) which is closed at the bottom by a bottom 5 and the top by a glass 6 bordered by a bezel 7. The central cavity 4 contains the main components of the diver's watch, including the circuit board printed 8 which carries the main electronic circuits of the watch.

0012As seen particularly in Figures 2 and 4, the sensor pressure 10 is placed in a housing 11 arranged in middle part 3 and opening on the outside left 9 of the housing 2, so that the sensor can be mounted in this housing from outside the housing. The sensor 10 is held in this housing using two elements shown in Figure 2, namely an O-ring seal 12 and a cap 13, and is further protected by a screen formed by a perforated plate 14 mounted inside the hood 13. On the outside, the hood surface 13 is preferably, but not necessarily, flush with the outer face 9 side of the housing. This face is never in contact with the wrist 15 of the wearer when the wristwatch is worn, so that the ambient pressure reaches this surface of the cover without restraint, either in air or in water.

0013The pressure sensor 10 is of known construction. It has an element piezoresistive silicon 16, mounted on a square ceramic substrate 17 provided with conductors connecting the element 16 to the contact pads disposed on the back of substrate. These pads make contact with a printed circuit film 18 applied behind the substrate 17. The sensor 10 further includes a cylindrical sidewall 20 which is fixed to the front face of the substrate 17 and form therewith a shaped structure pot which surrounds the silicon member 16, which is coated by a silicone gel 21 whose front surface 22 is the exposed surface of the sensor, for receiving ambient pressure.

0014As seen particularly in Figure 3, the housing 11 provided for the sensor in the middle of the housing has a bottom wall 24 and substantially flat square, against which support the sensor structure and the printed circuit film 18 and in which is provided a window 25 which communicates the housing 11 with the central cavity 4. The housing 11 is delimited laterally by a wall circular protrusion 26 having a discontinuous radial flange 27 on its outer surface. This flange extends in a groove 28 surrounding the wall 26 over its entire circumference, except in sectors provided with a blind guide hole 29.

0015The gasket 12 of elastomer is disposed around the side wall 20 sensor and is compressed radially between said wall and the protruding wall 26 of housing 11. It thus ensures not only sealing but also a suspension elastic protecting the sensor against shocks that could suffer the case.

0016As can be seen in particular in Figures 2 and 5, the cap 13 is of preferably molded of opaque plastic or provided with a opaque coating. It comprises in its central region an outer wall 31 in circular plate of variable thickness, traversed by three holes 32 which have a diameter of about 1.5 mm in this example. These orifices open outwardly in respective concave surfaces 33 whose effect is both decorative and functional, to prevent the orifice is sealed by an easily flat foreign body. On its inner face, the wall 31 of this cover surfaces prominent 34 and 35 to support the protection plate 14 shoulders 36 side to laterally wedge the plate and three pins 37 whose role appear later. The periphery of cap 13 includes a circular flange 38 arranged to hook onto the outer rim 27 of the wall 26 of the Housing sensor, so that the cap 13 can be fixed simply by clipping on the housing 2. Thus, the hood is secure, but we can pull it off in case it should change the sensor 10. The cover further comprises a guide finger 39 which engages in the hole 29 to ensure proper orientation of the cap, so the position due to its three ports 32.

0017Figure 6 shows in more detail the configuration of the protection plate 14, which is, in this example, a simple circular plate plastic enough rigid, such as Kapton®, but may be made of any rigid material resistant to corrosion, particularly in the presence of sea water. On its periphery are provided three jack notches 40, intended to cooperate with the shoulders 36 of the hood 13, and a registration notch 41 serving to mechanized positioning of the plate in the cover. The notch 41 can also be used visual cue for manual introduction of the plate. Small parts projections 44 (Figure 5) are formed on the inside of the cover to retain the plate 14 by their elasticity.

0018The plate 14 is pierced with a plurality of holes 42 to allow the ambient pressure to be transmitted toward the sensor 10. In the present example, there is provided a twenty holes 42 having a diameter of about 0.5 mm. All these holes are distinctly laterally offset relative to the openings 32 of the cover 13, holes whose projected position perpendicular to the plate 14 is shown in Figure 6 by three circles 32a. The holes 42 are distributed over the plate 14 so that none of them is less than 0.75 mm from one of 32a circles. will also be noted that three of the holes 42 are arranged so as to be traversed by the pins 37 of the lid, which can abut against the face end of the cylindrical wall 20 of the sensor 10 to retain it in its housing.

0019The protection plate 14 once it is placed within the cap 13, is located at a constant distance of about 0.1 mm from the wall 31 of the hood. Accordingly, the ambient pressure outside of the housing 2 is transmits to the exposed surface 22 of the sensor 10 by passing through the orifices 32 of cover, and then following a distance the gap of 0.1 mm between the plates 14 and 31, and finally through the holes 42 of the plate 14 to achieve in the housing 11 of the sensor. Thus, any transmission path of the pressure ambient to the exposed surface 22 of the sensor is highly tortuous. Firstly, This eliminates any risk of damaging the sensor by ingress of foreign bodies, particularly as the interval between the two plates is very small. Preferably the thickness of this gap is less than 0.2 mm to prevent the penetration of foreign bodies such as grains of sand. Moreover, this keeps the sensor largely immune to external light, so the gel coating the element 21 silicon need not be opaque or covered with an opaque membrane. Good Naturally, the transmission of light along the transmission paths of the ambient pressure can be further reduced if the plates 14 and 31 have a color dark along these paths.

0020Thus, we see that the protective plate 14 is a screen at a time very effective and simple to manufacture and assemble, preventing the intrusion of body foreign and ambient light to the sensor. A significant advantage of this type screen is to allow to place the orifice 32 of the cover 13 opposite the exposed surface 22 of the sensor, even at the hood center, which reduces to a minimum exterior dimensions of the hood, its diameter in this case. This aspect is particularly advantageous when the present invention is applied to a wristwatch, because it allows to place the pressure sensor discretely in a side of the case without affecting the overall aesthetics of the shows.

0021In Figure 4, we see that the electrical connection between the sensor pressure 10 and the card main circuit 8 of the watch is assured means of four flexible contact blades 46 which are embedded by molding in a block 47 of insulating plastics material and emerge on the other side of this block in the form of tabs 48 which are connectable by soldering to circuits of the card 8. The block 47 is provided with feet 49 for fixing by heat sealing to the plate 50 supporting the movement, as well as other not shown for the feet precisely positioned relative to the plate 50 and the card 8.

0022The leaf springs 46 extend through the window 25 and through apply their elasticity against the contact pads provided on the printed circuit 18 backed the sensor 10, which ensures a good transmission of electrical signals output of the sensor even if the latter moves slightly under the effect of an impact. But the main advantage of this arrangement is to facilitate the assembly of components of the watch. For example, you can mount the pressure sensor 10 in the middle part 3 housing and fasten using the cap 13 before beginning assembly General and shows in particular the mounting of the components in its cavity Central 4. During assembly, it is then placed in this cavity the module preassembled electronic map 8, such that the contact blades flexible 46 will automatically establish a correct electrical contact with the sensor 10. Conversely, one can choose to install the pressure sensor 10 in the middle part 3 after mounting of the internal components of the watch, especially if it is wishes to perform tests using the contact blades 46 before mounting the sensor.

0023Of course, it is also possible to make the electrical connection between the elements 8 and 10 through the window 25 of another known manner, for example by using a flat cable plug on the map 8.

0024While the shield described above with reference to the drawings is formed by adding a simple perforated plate, it could be done otherwise without departing from the scope of the invention defined by the claims. For example, the screen protection could have two parallel perforated plates and spaced from each other, the respective holes of the plates being laterally offset to one another so that an orthogonal projection of the holes of one of the plates on the other plate is spaced holes thereof. In another variant, the shield could comprise a flat element thicker than a plate containing in its thickness a plurality of channels extending in its median plane and whose would lead ends respectively on both sides of this element. We can easily achieve such an assembly element by two molded plates synthetic material, the channels being formed on a face of one of the plates.

0025The applications of the invention are not limited to the example described above, but extend to all portable electronic device with a sensor Pressure mounted in a housing which leads to outside of the housing of the apparatus, for example an altimeter or a dive computer.