EP0899635B1 - Device for immersion in water and comprising a sound transducer - Google Patents

Description

The present invention relates to an apparatus likely to be immersed in a liquid such as water, such as devices worn on the wrist such as than watches. More particularly, the invention relates to such apparatus in the case of which is mounted a sound transducer.

To guarantee the water resistance of watches worn on the wrist at a depth of immersion that can nominally reach thirty meters it is already known to mount an acoustic transducer in the watch case without providing a way of communication between the transducer and the outside likely to conduct sound waves directly (CH-A-375 664). A such mounting has the advantage of guaranteeing very good waterproofness of the watch. On the other hand, the acoustic energy to reach or be emitted by the transducer through the solid wall of the housing, this solution is not possible only if we are satisfied with a sound quality poor. Indeed, the usable frequency band is then limited to frequencies that manage to cross this wall. In practice, we have to work with resonant frequencies of the transducer, these frequencies can be effectively transmitted through the wall of the case that if they correspond to a frequency of resonance of this wall. This necessarily limits the frequency range that can be transmitted and is therefore not suitable for reproducing and / or receiving sounds complex such as speech or music. We will note also that such a wall annoyingly dampens the transmission of sounds that can be emitted or received by the transducer.

The object of the invention is to provide an apparatus for type indicated above fitted with a sound transducer so that we can work with a broad spectrum sound, in particular the sound spectrum corresponding to the speech, while ensuring a high degree of tightness.

• ledit transducteur sonore est solidaire d'une membrane déformable le séparant de façon étanche d'une cavité d'entrée qui est ménagée dans ledit boítier et en communication directe avec l'extérieur, en ce que ladite membrane est appliquée élastiquement par sa-périphérie sur une surface d'appui ménagée autour de ladite cavité en séparant celle-ci de façon étanche d'une chambre de déformation ménagée dans ledit boítier du côté de la membrane opposée à ladite cavité tout en étant en communication avec l'intérieur de ce boítier, et en ce que le fond de ladite chambre de déformation forme une surface de soutien pour ladite membrane lorsqu'une pression statique extérieure supérieure à une valeur prédéterminée lui est appliquée.

The invention therefore relates to a waterproof portable device capable of undergoing immersion to a predetermined depth of a liquid such as water, in particular waterproof watch, comprising a housing in which is mounted a sound transducer so as to communicate in a fluid-tight manner with the outside of the housing by means of sound energy, characterized in that

• said sound transducer is integral with a deformable membrane sealingly separating it from an inlet cavity which is formed in said housing and in direct communication with the outside, in that said membrane is applied elastically by its periphery to a bearing surface formed around said cavity by separating the latter in a sealed manner from a deformation chamber formed in said housing on the side of the membrane opposite to said cavity while being in communication with the interior of this housing, and in that the bottom of said deformation chamber forms a support surface for said membrane when an external static pressure greater than a predetermined value is applied to it.

Thanks to these features, the sound transducer can receive or emit sound energy by through the membrane which, being suspended only by its peripheral edge in the case, can vibrate freely without hindering the transmission / reception of this sound energy to or from the transducer.

The membrane can be kept pressed against the bearing surface of the housing by means of a member elastic bearing on the bottom of the deformation and acting on the edge of the membrane.

Alternatively, however, the membrane may be kept pressed against its bearing surface by virtue of its own elasticity by being mounted taut in the housing.

• la figure 1 montre une vue en coupe d'une pièce d'horlogerie conçue selon l'invention et munie d'un transducteur qui dans cet exemple est un haut-parleur;
• la figure 2 est une vue schématique en coupe d'une variante de l'invention; et
• la figure 3 représente un détail des moyens élastiques maintenant l'ensemble transducteur en position contre une surface d'appui.

Other characteristics and advantages of the invention will become apparent during the description which follows, given solely by way of example and made with reference to the appended drawings in which:

• Figure 1 shows a sectional view of a timepiece designed according to the invention and provided with a transducer which in this example is a speaker;
• Figure 2 is a schematic sectional view of a variant of the invention; and
• Figure 3 shows a detail of the elastic means holding the transducer assembly in position against a bearing surface.

In the description which follows, the invention will be illustrated in its application to a timepiece such as a wristwatch. It is clear, however, that the invention can be applied to any other apparatus, usually portable and small, and in front include at least one sound transducer, the switchgear being further capable of being immersed in a liquid such as water to a predetermined depth. In Furthermore, in the example described, the sound transducer is a speaker, however a transducer microphone can also be used to advantage with the invention.

This being so, we see represented in FIG. 1, a sectional view of a wristwatch 1 which is guaranteed sealing up to a predetermined water depth, a depth of 30 m being a predicted value often in convenient.

We recognize from watch 1 in Figure 1 the case 2, glass 3, hands 4 and 5, dial 6 and some parts of the time setting mechanism 7. All these elements, as well as those simply sketched out, even not visible in FIG. 1, like the integrated circuit, the quartz, miniature motor, cog etc. are conventional and therefore need not be described here. Although this is not a limiting application - of the invention, the apparatus according to the invention provided with the microphone or speaker transducer may advantageously be a watch forming a telephone portable.

In the case shown, the housing 2 has a bottom 8 doubled by a support disc 9 superimposed on this bottom 8 in the housing 2 and secured to it by any means suitable, for example by gluing or clipping.

The bottom 8 has a cavity or inlet chamber 10 generally circular in shape and connected to outside through a channel 11 which leads to it laterally. Around the cavity 10, the bottom 8 has a circular bearing surface 12 which, in the present example, is slightly inclined to the axis of the cavity 10.

Opposite the bottom cavity 10, the disc of support 9 has a recess 13 of general shape circular and roughly coaxial to cavity 10 while having a slightly larger diameter. This recess 13 constitutes a deformation chamber. It is bordered by a peripheral rib 14 with rounded edge and contiguous with a annular groove 15 located inside with respect at rib 14.

In the volume constituted by the cavity 10 at the bottom 8 and the recess 13 of the support disc 9 is arranged a sound transducer assembly 16. This assembly includes a membrane 17 formed of a circular disc which is came from forming a peripheral rim 18 whose surface outside is fixed by gluing to a side wall peripheral 19 formed around the bearing surface 12 respectively on the bottom 8 and the support disc 9. Thus, the membrane 17 seals the interior of the watch 1 vis-à-vis the outside.

In the area inside the inner edge of the bearing surface 12, the membrane 17 is free to deform. It is pressed against this support surface by an elastic member 20 in order to allow the mode lower frequency vibration of the active part of the transducer 16. The latter is formed for example of a ring housed in the groove 15 of the support disc 9 and provided with elastic legs 21 in the form of a Z (FIG. 3), for example ten in number for a diameter of about 25 mm from membrane 17, which are cut out and folded out from its plane towards the membrane 17. The legs elastic 21 are under stress and therefore apply the membrane against the bearing surface 12 delimiting strictly the area of the membrane that can vibrate freely. As an indication, the elastic ring 20 develops a total strength of the order of 250 to 600 g. We understands that this force depends on the diameter of the membrane, its thickness and the sound frequencies that you want to send or receive.

The transducer assembly 16 also includes a transducer element 22 (forming the active part of the transducer) which, in the case shown, is a loudspeaker piezoelectric type. It can also be receiver (microphone function). In the case shown here, it has a metal blade interposed between two piezoelectric discs (not visible in Figure 1), the assembly being suitably connected to a circuit of control or an operating circuit (not detailed) housed in the housing 2. The transducer element 22 is bonded to the membrane 17 on the side of the recess 13 in the area of free vibration of it. It is available in the trade with the Murata Company, Japan. According to one variant, the transducer element 22 can also be secured to the membrane during molding thereof, either by being partially incorporated therein, or by being overmolded by the membrane material.

It should be noted that the legs 21 exert their pressure preferably on the extreme edge of the element transducer 22 so that it can transmit a frequency as low as possible for a given diameter. The tabs 21 bear against the edge of the blade metal of the transducer element 22 by through which they support the membrane 17 on the surface 12.

In order to avoid distortions, care should be taken that the support forces exerted by the elastic tabs 21 is sufficient to maintain the transducer element 22 against the bearing surface, i.e. it is permanently maintained during operation. However, these forces should not block its orientation (i.e. correspond to embedding) which would typically lead to a doubling of the fundamental frequency of the transducer element.

The recess 13 forms an internal chamber which is in communication with the interior of the housing 2 through through holes 23 formed in the bottom 13a of the recess 13. The membrane 17 can therefore deform in this internal chamber or recess 13 until applied against its bottom 13a. This thus constitutes a surface stop for diaphragm 17 if the differential pressure on both sides of the membrane exceeds a value predetermined.

The membrane 17 is preferably made of silicone and can have a thickness of around 300 µm, its diameter may be 25 mm, for example.

In an area away from the whole that we come to describe, the bottom 8 and the support disc 9 have a through passage 24 having a shoulder 25 against which is disposed a compensation disc 26 pressure. This is waterproof, but breathable provided that the variation in pressure difference on either side of this pastille varies very slowly. It can be done in Sintered Teflon® for example. This tablet can be assimilated to a low-pass filter allowing air to pass through the pressure varies at very low frequency (1/10 Hz, for example). This structure allows adaptation to variations in static pressure resulting for example variations in altitude and / or climatic conditions, when the watch is worn.

Note however that the membrane 17 itself can be designed in such a way that it fulfills the function pressure compensation in place of the pad 26. In this case, this membrane must be made in one flexible and semi-permeable gas material whose pressure static varies at very low frequency.

The behavior of the membrane 17 is as follows.

When the watch is worn out of the water, the membrane 17 has a flat configuration in which it is free to vibrate so to transmit to outside without disturbing sound vibrations produced by element 22.

However, when the watch comes to be submerged, the membrane 17 will deform due to an abrupt variation of the differential pressure which prevails two sides. It will then assume a domed shape in bottom direction 13a, the compensation path of pressure through passage 26 not reaching enough quickly to balance the difference in pressures. AT from a certain hydrostatic pressure value, the deformation of membrane 17 will be such that it will apply against the bottom 13a of the recess 13, which thus provides effective support preventing any deterioration of the membrane 17 and of the element transducer 22.

Figure 2 very schematically shows a variant of the invention in which an apparatus 1A has a 2A box with an inlet chamber circular 27. This can be arranged in the same way than that formed by the cavity 10 in FIG. 1. Around from the edge of this chamber 27 is formed, facing inside, an annular rib 28 which defines a bearing surface 12A. Around this rib is provided a first groove 29 in the outer wall of which opens a second groove 30.

The apparatus also includes a 17A membrane whose outer edge is received in the second groove 30 to be securely attached, for example by gluing. The membrane 17A has inherent elasticity and is fixed in the groove 30 so as to be under a slight constraint. Because of this, it is stretched over the surface support 12A formed on the annular rib 28 which protrudes from a certain distance the bottom of the first groove 29. A sound converter element 22A is fixed on the membrane 17A.

Behind the membrane 17A, on the inside, is in besides provided a support grid 31 forming the bottom of a deformation chamber 13A. This grid is provided through orifices 32 and makes it possible to maintain the membrane 17 in the event of overpressure exerted on it since outside.

A passage 24A can be provided in the wall of the box 2A and be closed by a balancing disc pressure 26A, as in the embodiment of the figure 1.

The arrangement of Figure 2 differs from that of Figure 1 in that it does not include any elastic means special to ensure the application of the membrane against an element of the housing, the elasticity necessary for this purpose being due to that inherent in the membrane itself.

Claims (13)

1. Portable water resistant device capable of undergoing submersion to a predetermined depth in a liquid such as water, in particular a water resistant watch, including a case (2; 2A) in which is mounted an acoustic transducer (22; 22A) so as to communicate in a water tight manner with the exterior of the case (2; 2A) via acoustic energy, characterised in that

   said acoustic transducer (22; 22A) is attached to a membrane (17; 17A) which is able to be deformed, separating it in a watertight manner from an inlet cavity (10, 11; 27) which is arranged in said case (2; 2A) and in direct communication with the exterior, in that said membrane (17, 17A) is resiliently applied by its periphery onto a rest surface (12, 12A) arranged around said cavity separating the latter in a watertight manner from a deformation chamber (13; 13A) arranged in said case (2, 2A) on the side of the membrane (17; 17A) opposite to said cavity (10, 11; 27) while being in communication with the interior of said case, and in that the bottom (13, 13A) forms a support surface for said membrane (17; 17A) when an external static pressure greater than a predetermined value is applied thereto.
2. Device according to claim 1, characterised in that it includes a resilient element (20, 21) resting on the bottom (13a) of said deformation chamber (13) and holding the periphery of said membrane (17) applied against said rest surface (12).
3. Device according to claim 2, characterised in that said resilient element is a ring (20) made of a resilient material arranged above the periphery of the membrane (17) and including several support lugs (21) bent outside the plane thereof and resting on said periphery.
4. Device according to claim 1, characterised in that said membrane (17A) is on said rest surface (12A) by virtue of its own resilience by being mounted taut in said case (2A).
5. Device according to any one of claims 1 to 3, characterised in that said membrane (17) has a peripheral rim (18) extending beyond the plane thereof and by means of which it is bonded to the lateral wall of said deformation chamber (13).
6. Device according to any one of claims to 5, characterised in that said deformation chamber (13; 13A) is placed in communication with the exterior by means (24, 25, 26; 24A, 26A) for balancing the slow variations in the differential pressure on either side of said membrane (17; 17A).
7. Device according to claim 6, characterised in that said balancing means are formed by the membrane itself.
8. Device according to claim 6, characterised in that said pressure balancing means include a disc (26; 26A) placed in a passage (24; 24A) arranged in the wall of said case (2; 2A), said passage being in communication on the one hand with the exterior and on the other hand with said deformation chamber (13; 13A), and in that said disc (26; 26A) is made of a material which only allows a flow of air when there are slow variations in the differential pressure of its two sides.
9. Device according to any of claim 8,
   characterised in that said disc (26; 26A) is made of sintered Teflon® or ceramic material.
10. Device according to any one of the preceding claims, characterised in that said acoustic transducer (22) is a microphone or a loud-speaker.
11. Device according to any one of the preceding claims, characterised in that said membrane (17; 17A) is made of silicon.
12. Device according to any one of the preceding claims, characterised in that said membrane has a thickness of 300 µm for a diameter of 25 mm.
13. Device according to any one of the preceding claims, characterised in that the bottom (31) of said deformation chamber (13A) is a perforated grid.

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