Portable electronic device comprising a pressure sensor

p0001The present invention relates to a portable electronic device to the wrist, in particular a wristwatch for divers, a depth gauge or an altimeter, having a housing and a pressure sensor which is mounted in a housing of the casing and has a surface exposed to the interior 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 one orifice to the housing for transmitting the ambient pressure outside the housing to housing.

p0002Discloses a wristwatch of this kind, described in the patent <patcit id="pcit0001" dnum="EP195636A"><text>EP 195 636</text></patcit>Wherein the housing of the pressure sensor is provided in a side projection of the housing and opens onto the upper face of the housing, so that it can set up the sensor from above. According to a construction which is the most common at present, the pressure sensor comprises a silicon piezo-resistive element which is accommodated in a cup-shaped structure and coated with a silicone gel to be protected from the effects of water . This gel is further coated with a flexible layer made of silicone rubber or resin, which forms the exposed surface of the sensor and transmits the ambient pressure piezo-resistive element. Above, the cover closing the housing is formed by a perforated circular plate. The holes in said plate are arranged along its periphery, so as not to be in front of 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 freezing.

p0003However, such an arrangement has two disadvantages. On the one hand, it requires to 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 silicon element to prolonged exposure to sunlight, but the construction described above does not sufficiently stops diffusion of light in the sensor.

p0004In Patent <patcit id="pcit0002" dnum="EP677798A"><text>EP 677 798</text></patcit>There is disclosed a wrist 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 watchcase. To prevent the support of the housing against the wearer's wrist hinders the transmission of ambient pressure to the sensor, the back of the case has grooves, while the housing is covered with a lid or cap bearing in outside a bearing surface located flush with the back of the body to bear against the wearer's wrist and leave behind the cover or through the side openings communicating between the grooves and the sensor housing. Such a construction has the drawback to lead to a large thickness of the watch. Moreover, it is not arranged to prevent sunlight from reaching the sensor, especially when the watch is not put on the wrist.

p0005Also known are portable electronic devices to the wrist as described in <patcit id="pcit0003" dnum="EP1006418A"><text>EP 1006418</text></patcit> or in <patcit id="pcit0004" dnum="JP2002323581A"><text>JP 2002 323581</text></patcit>.

p0006These documents disclose devices according to the preamble of claim 1.

Summary of the Invention

p0007The present invention aims to overcome the aforementioned disadvantages of the prior art, thanks to a particularly simple and effective arrangement of the sensor mounting bodies in housing intended for it. A particular object is to design these members so as to simplify to a large extent the installation of the sensor and components of the device associated to it, in particular for an automated mounting.

p0008To this end, the invention relates to a portable electronic apparatus as defined in claim 1.

p0009Thus, the protective shield provided in this invention provides double 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, for example with the addition of a plate having suitably positioned holes in the cover closing the housing of the pressure sensor. In addition, this construction advantageously allows placement or the external openings of the cover to the exposed surface of the sensor, so in the central region of the cover, which reduces the external dimensions and the visual impact of the cover. The side of the housing having the housing for the sensor can also be a side face as the upper face of the housing.

p0010Especially 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 of the perforated plate being laterally offset from each hood opening so that an orthogonal projection of the orifice on the perforated plate is spaced holes thereof.

p0011Other 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

p0012<ul><li>The <figref idrefs="f0001">figure 1</figref> is a side view of a wristwatch comprising a pressure sensor and arranged according to the principles of the present invention.</li><li>The <figref idrefs="f0001">2</figref> is an exploded perspective view of the pressure sensor and its mounting members in the watch case of the <figref idrefs="f0001">figure 1</figref>.</li><li>The <figref idrefs="f0002">3</figref> is a front view of the housing for the pressure sensor.</li><li>The <figref idrefs="f0003">4</figref> is a partial sectional view of the watch according to line IV-IV of <figref idrefs="f0001">figure 1</figref>.</li><li>The <figref idrefs="f0004">5</figref> is a perspective view of the rear face of a cap shown in <figref idrefs="f0001">2</figref>.</li><li>The <figref idrefs="f0005">6</figref> is a front view of a protective plate shown in <figref idrefs="f0001">2</figref>.</li></ul>

detailed description of an embodiment of the invention

p0013With reference to <figref idrefs="f0001 f0002 f0003">Figures 1 to 4</figref>, A wristwatch 1 to plunger has a housing 2 of rigid synthetic material which contains in particular an electronic watch movement, a pressure sensor sensitive to the ambient pressure outside of the housing, the analog display organs and / or digital and electronic circuits for processing pressure information and display results by the display means. The housing 2 comprises a middle part 3 of synthetic material, surrounding a central cavity 4 (<figref idrefs="f0003">4</figref>) 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 major components of the diver's watch, including the printed circuit board 8 which carries the main circuits electronic watch.

p0014As seen particularly in <figref idrefs="f0001">figures 2</figref> and <figref idrefs="f0003">4</figref>, The pressure sensor 10 is placed in a housing 11 arranged in middle part 3 and opening on the outer left wall 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 with two elements shown in<figref idrefs="f0001">2</figref>, 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 lateral surface 9 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.

p0015The pressure sensor 10 is of known construction. It comprises a piezo-resistive element 16 made of silicon, mounted on a square ceramic substrate 17 provided with conductors connecting the element 16 to the contact pads disposed on the back of the substrate. These pads make contact with a printed circuit film 18 applied behind the substrate 17. The sensor 10 further includes a cylindrical side wall 20 which is fixed on the front face of the substrate 17 and form with the latter a pot-shaped structure surrounding 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 the ambient pressure.

p0016As seen particularly in the <figref idrefs="f0002">3</figref>, 11 provided for housing the sensor in the middle part of the housing has a bottom wall 24 flat and substantially square, against which support the sensor structure and the printed circuit film 18 and in which is provided a window 25 which is the housing 11 communicate with the central cavity 4. the housing 11 is laterally delimited by a projecting circular wall 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 an area provided with a blind guide hole 29.

p001712 the elastomeric seal is disposed around the side wall 20 of the sensor and is compressed radially between said wall and the protruding wall 26 of the housing 11. It thus not only provides a seal, but also a resilient suspension protecting the sensor against shocks that could suffer the case.

p0018As seen particularly in <figref idrefs="f0001">figures 2</figref> and <figref idrefs="f0004">5</figref>The cap 13 is preferably molded of opaque plastic or provided with an opaque coating. It comprises in its central region a circular plate outer wall 31 in the form of varying 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 easily blocked by a foreign body flat. On its inside wall 31 of this prominent hood surfaces 34 and 35 to support the protection plate 14, lateral shoulders 36 to laterally wedge the plate and three pins 37 whose role will appear later. The periphery of cap 13 includes a circular flange 38 arranged to hook over the outer edge 27 of the wall 26 of the sensor housing, so that the cover 13 can be fixed simply by clipping on the housing 2. Thus, the cover is secure, but we can pull it off in case it would change the sensor 10. the cover also includes a guide pin 39 which engages in the hole 29 to ensure proper orientation of the cap, so the desired position its three orifices 32.

p0019The <figref idrefs="f0005">6</figref> shows in more detail the configuration of the protective plate 14, which is, in this example, a simple circular plate relatively rigid synthetic material, for example 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 cover 13, and a locating notch 41 serving to mechanized positioning of the plate in the cover. The notch 41 may also serve as a visual cue for manual introduction of the plate. Small protrusions 44 (<figref idrefs="f0004">5</figref>) Are formed on the inside of the cover to retain the plate 14 by their elasticity.

p0020The 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 significantly offset laterally relative to the orifices 32 of the cover 13, holes whose position projected perpendicularly on the plate 14 is shown in<figref idrefs="f0005">6</figref> 32a by three circles. The holes 42 are distributed over the plate 14 so that none of them is less than 0.75 mm from one of circles 32a. It will also be noted that three of the holes 42 are arranged so as to be traversed by the studs 37 of the lid, which can abut against the end face of the cylindrical wall 20 of the sensor 10 to retain it in its housing.

p0021The protective plate 14, once it is in place inside the cap 13, is located at a constant distance of about 0.1 mm of the wall 31 of the cover. Accordingly, the ambient pressure outside of the housing 2 is transmitted to the exposed surface 22 of the sensor 10 by passing through the orifices 32 of the cover, then following on a distance gap of 0.1 mm between the plates 14 and 31, and finally through the holes 42 of the plate 14 to reach into the housing 11 of the sensor. Thus, any transmission path of the ambient pressure to the exposed surface 22 of the sensor is highly tortuous. On the one hand, 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 objects such as grains of sand. Moreover, this keeps the sensor largely immune to external light, so that the gel 21 coating the silicon element need not be opaque or covered with an opaque membrane. Of course, the transmission of light along the transmission paths of the ambient pressure can be further reduced if the plates 14 and 31 have a dark color along these paths.

p0022Thus, we see that the protective plate 14 is a screen both very effective and very simple to manufacture and assemble, preventing the intrusion of foreign bodies and ambient light to the sensor. A significant advantage of this type of display 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, thereby minimizing the external dimensions of hood, its diameter in this case. This is particularly advantageous when the invention is applied to a wristwatch because it allows placement discreetly pressure sensor in a side of the case without affecting the overall aesthetics of the watch.

p0023In the <figref idrefs="f0003">4</figref>, It is noted that the electrical connection between the pressure sensor 10 and the main printed circuit board 8 of the watch is provided by means of four flexible contact blades 46 which are embedded by molding in a block 47 of insulating plastics material and emerging 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, and other not shown feet to position it precisely relative to the plate 50 and the card 8.

p0024The leaf springs 46 extend through the window 25 and apply due to their elasticity against contact pads provided on the printed circuit 18 leaning against the sensor 10, which ensures a good transmission of electric signals output from the same sensor if it moves slightly under the effect of a shock. 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 of the housing and fix it using the cap 13, before beginning the general assembly of the watch, especially the assembly of its components in its central cavity 4. During assembly, it is then placed in this cavity the pre-assembled module on the electronic card 8, such that the flexible contact blades 46 will automatically establish a proper electrical contact with the sensor 10. Conversely, you can choose to install the pressure sensor 10 in the middle part 3 only after installation of interior elements of the watch, especially if we want to conduct tests using the contact blades 46 before mounting the sensor.

p0025Of course, it is also possible to achieve electrical connection between the elements 8 and 10 through the window 25 of another known manner, for example by means of a flat cable to be plugged into the card 8.

p0026While the shield described above with reference to the drawings is formed by adding a simple perforated plate, it could be achieved otherwise without departing from the scope of the invention defined by the claims. For example, the shield 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 orthogonal projection of the holes of one of the plates on the the other plate is spaced holes thereof. In another variant, the shield may comprise a flat element thicker than a plate and containing in its thickness a plurality of channels extending in its median plane and the ends of which would result on the two sides of this element. Can be easily realized such an element by assembling two molded plastic panels, the channels being formed on a face of one of the plates.

p0027applications of the invention are not limited to the example described above, but extend to any portable electronic apparatus comprising a pressure sensor mounted in a housing which opens on an outer face of the camera body, eg an altimeter or a dive computer.