HK1209825B - Pressure sensor - Google Patents

Description

Pressure sensor

Technical Field

The present invention relates to the field of pressure measurement devices, and more particularly, to a pressure sensor including a pressure sensing device that utilizes the propulsion of liquid within an enclosed volume to effect sensing when the sensor is subjected to external pressure. The invention also relates to a barometer device comprising a pressure sensor in which pressure information sensed by the sensor is transmitted and then displayed in the barometer device, for example using an indicator device, and/or used to control a predetermined operation. The barometer device may be included, particularly in small-sized portable items such as wristwatches.

Background

Wristwatches provided with pressure measuring means are known. These wristwatches, for example divers' wristwatches, often comprise pressure sensors, such as membrane sensors, the deformation of which varies with the pressure fluctuations encountered during diving. In one known embodiment, the change (value) in the geometry of the pressure sensor with the air pressure fluctuations is converted into a linear movement of a sensing arm which controls the pivoting of the lever. The pivoting movement of the lever is in turn converted into a rotary movement of a gear train which meshes with the display wheel with a transmission ratio calculated so that the pressure indicator hand carried by the display wheel provides the user of the watch with a clear indication of the pressure.

Structures of the type briefly described above are generally used to provide a pressure indication to the user of the watch during diving.

These mechanical pressure measurement and display devices are relatively complex and difficult to implement in view of the large number of mechanical components contained therein. Furthermore, it is necessary to provide communication between the outside of the watch case and the inside in which the device is mounted, which would lead to a complex configuration if it were necessary in all cases to ensure the watch is sealed. These factors therefore make it difficult to produce in an economical manner a watch equipped with a mechanical pressure measuring and display device.

A main object of the present invention is to provide a pressure sensor which is simple and economical to implement.

Another object of the present invention is to provide a pressure sensor having a structure that allows its easy integration into small-sized portable objects, in particular watches, without affecting the seal of the watch.

Disclosure of Invention

To achieve the above object, according to a first aspect, the present invention relates to a pressure sensor comprising means for sensing pressure and converting the pressure into an electrical signal that can be transmitted by an electrical circuit to a control interface circuit of an indicator device, characterized in that said sensing and converting means comprise:

-an enclosed volume/space and a liquid contained in the enclosed volume, the liquid being electrically conductive and movable within the enclosed volume,

-at least one sensing element arranged at a specified position inside the enclosed volume, the sensing element comprising at least one pair of electrodes and cooperating with the liquid when the liquid moves within the enclosed volume such that the electrical circuit is closed when the liquid passes the sensing element.

According to a particular feature, the closed volume comprises a first portion forming a reservoir in which the liquid is contained without pressure and a second portion forming a capillary tube, and moves from the reservoir towards the capillary tube into the capillary tube when subjected to pressure.

According to one particular feature, the sensing element is arranged along the capillary. Thus, when pressure acts on the reservoir, the sensing element may sense liquid traveling within the capillary.

Preferably, the pressure sensor further comprises first and second substrates stacked, and a sealing frame joining the first and second substrates to define the enclosed volume therebetween.

According to a second aspect, the invention relates to a barometer device comprising a pressure sensor according to the first aspect of the invention.

In addition to the pressure sensor of the present invention, the barometer device further comprises:

-at least one indicator device for indicating the position of the object,

-an electrical circuit comprising a control interface circuit for the indicator device for transmitting a pressure-related electrical signal to the indicator device, an

-at least one energy source for said electric circuit.

According to a third aspect of the invention, the invention relates to a timepiece comprising a pressure measuring device according to the second aspect of the invention.

Preferably, the reservoir and the capillary of the pressure sensor extend in a substantially circular direction, which advantageously enables the sensor to be housed under the timepiece mirror or inside a timepiece bezel.

According to a particular embodiment, the indicator device comprises a display screen and/or a sound emitter and/or a light emitter associated with the pressure sensor, in particular with its electric circuit.

Drawings

The invention will be better understood on reading the following description of a particular embodiment, provided by way of non-limiting example and illustrated with the aid of the attached drawings, in which:

fig. 1 shows a top view of a timepiece provided with a pressure sensor housed under a mirror, according to a first embodiment of the invention.

Fig. 2 is a cross-sectional view taken along line a-a in fig. 1 showing a first variant embodiment.

Figures 3 and 4 show a perspective top view and a top view, respectively, of a pressure sensor housed inside a timepiece bezel (bezel) according to a second embodiment of the invention.

Fig. 5 to 7 are partial cross-sectional views taken along lines i-i, ii-ii, iii-iii in fig. 4 showing the arrangement of the pressure sensors inside the bezel.

Detailed Description

Referring first to fig. 1 and 2, there is shown a pressure measuring device 100, such as a depth gauge, the pressure measuring device 100 taking the form of a wristwatch-type timepiece 2. Timepiece 2 comprises, in a conventional manner, a case 4, said case 4 comprising an intermediate part 6, a mirror 8 and a back cover 10, these parts defining a space 12 for receiving movement M (fig. 2). The watch also comprises a winding crown 14, a dial 16 and hands 18.

Timepiece 2, which timepiece 2 is also a pressure measuring device 100 in this example, includes a depth indicator device 20, for example in the form of a liquid crystal display device, and a pressure sensor 22.

In the example of fig. 1, the pressure sensor 22 also functions as a watch mirror 8, here in the form of an at least partially transparent glass or composite component covering the entire dial 16 in a conventional manner.

The pressure sensor 22 comprises a closed volume formed by two consecutive parts. One of these two components is in the form of a reservoir 24 and the other component is in the form of a capillary tube 26, which capillary tube 26 is closed at one end and communicates with reservoir 24 at the other end.

The enclosed volume formed by reservoir 24 and capillary 26 is defined by upper and lower substrates 8a and 8b forming watch mirror 8. The upper substrate 8a and the lower substrate 8b are joined in the form of a liquid crystal cell by a sealing frame 28 having a closed contour, and the shape of the sealing frame 28 defines the dimensions of the reservoir 24 and the capillary 26.

The base plates 8a, 8b are in the form of discs having a diameter substantially equal to the diameter of the upper aperture 6a of the intermediate member 6. A sealing ring 30 is advantageously provided in the orifice 6a between the intermediate part 6 and the sensor assembly, in order to fix said assembly to the watch case in a conventional sealed manner, said assembly resting on a shoulder 6a provided inside the intermediate part 6. The flange 32 keeps the watch crystal 8 at a distance from the dial 16.

The sensor 22 also includes an outer sealing frame 34 disposed between the peripheral edges of the substrates 8a and 8 b.

The sealing frame 28 serves as a spacer between the upper substrate 8a and the lower substrate 8 b. The substrate forming the sensor is made of an insulating material. In the embodiment shown, in which the sensor is integrated into the timepiece above the display device and forms the mirror 8, the upper 8a and lower 8b substrates are made of transparent material and are arranged so that the conventional time display information of the timepiece 2 can be read out.

The thickness of substrates 8a and 8b is designed such that they can be bent at least in their region above reservoir 24. Typically, the thickness of these substrates, at least in the region of the reservoir, is about 0.1 mm. Thus, when the reservoir has a projection of 150mm onto the plane of the substrate²And the capillary has a projection of 70mm onto the plane of the substrate²A pressure range of 1 to 6 bar can be sensed, the cross-sectional area of the capillary being typically about 0.1mm²。

According to a preferred variant, the upper substrate 8a has a smaller thickness than the lower substrate 8b, so that the upper substrate subjected to the pressure can flex independently of the lower substrate 8 b. Thus, the response/sensitivity to pressure variations is improved, while the mechanical stability of the assembly remains compatible with the strength and rigidity requirements of the timepiece mirror.

By way of example, a suitable transparent material may be glass, a plastic material or sapphire.

According to a variant in which the sensor is not integrated above the display device, as shown in figures 3 to 7, which will be described in greater detail below, the upper 8a and lower 8b substrates may be made of an opaque material, such as plastic or opaque ceramic, for example when the sensor is integrated within a watch bezel.

In the embodiment shown in fig. 3 and 4, reservoir 24 and capillary 26 are arranged in a substantially circular orientation for insertion of sensor 22 into timepiece 2. Of course, a configuration of the reservoirs and capillaries in a linear direction, or any other non-linear and non-circular configuration is contemplated.

The sensor 22 of the present invention also includes a conductive liquid 36. Liquids that are particularly suitable due to their electrically conductive properties may be, for example, mineral/mineralized water, mercury or any other electrically conductive liquid. The liquid 36 is confined within the enclosed volume formed by reservoir 24 and capillary 26.

When pressure measurement device 100 is at atmospheric pressure, liquid 36 is contained entirely within reservoir 24 (fig. 1). When pressure measurement device 100 is subjected to pressure due to depth, pressure is applied to reservoir 24 over the entire surface of reservoir 24 projected onto the substrate. Upper substrate 8a is at least partially curved in its area near reservoir 24. Liquid 36 is then forced out of reservoir 24 to move to capillary 26.

The higher the pressure applied, the greater the distance the liquid 36 travels within the capillary tube 26. Thus, the amount of pressure acting on the pressure measurement device 100 may be determined by measuring the distance traveled by the liquid 36 within the capillary tube 26. To accomplish this, pressure sensor 22 also includes sensing and converting means for sensing the presence of liquid 36 within capillary tube 26 and converting it into information that is readily understood by a user.

According to one feature of the invention, the liquid 36 is electrically conductive. The liquid 36 cooperates with a sensing and converting means comprising an electrical circuit 38 and at least one sensing element 40 (fig. 2) placed on said electrical circuit. Advantageously, the circuit 38 with the various constituent components (energy source, conductive path PC, zebra connector Z, user interface microcontroller MC, display 20) is carried by a substrate S arranged below the dial 16. According to a variant, circuit 38 may be connected to a control circuit of timepiece movement M and share common components with this control circuit.

The sensing element 40 comprises at least one pair of electrodes 40a, 40 b. The pair of electrodes are arranged on the surface of the upper substrate 8a and/or the lower substrate 8b, said upper substrate 8a and/or lower substrate 8b being in contact with the liquid 36 along the capillary 26. Generally, the electrodes are made of a material such as Indium Tin Oxide (ITO), which has the advantage of being electrically conductive and optically transparent. There are other possible materials for making the electrodes, such as nanowire conductors (AG nanowires) or other layered conductive materials that are thin enough to be invisible.

Under the pressure applied to the sensor surface, liquid 36 is forced out of reservoir 24 and into capillary 26. When the liquid 36 comes into contact with the sensing element 40, an electrical contact between the pair of electrodes 40a, 40b is formed due to the conductivity of the liquid 36, and thus the sensing circuit 38 is closed. The electrical signal is then passed to the interface control circuitry of the indicator device 20, which indicator device 20 indicates to the user that the first pressure threshold has been passed. When the liquid 36 comes into contact with the sensing element 40 along the capillary tube 26, the electrical contact closes again and then passes a second electrical signal to the interface control circuit of the indicator device, which indicates to the user that a second pressure threshold has been passed, and so on.

The electrodes 40a, 40b of the pair of electrodes are arranged either juxtaposed on the upper substrate 8a or the lower substrate 8b (fig. 1), or are arranged facing each other between the upper substrate 8a and the lower substrate 8b (not shown).

Thus, by arranging the sensing elements 40 at appropriate distances from each other along the capillary tube 26, it is possible to not only sense the pressure exerted on the reservoir 24, but also quantify and/or determine the pressure threshold that is passed in succession. Typically, the sensing elements are spaced from each other at a distance that can allow providing stage related information to the diver.

The pressure related information is thus converted into an electrical signal which is communicated by means of the electrically conductive path to a control interface circuit of an indicator device such as the display device 20.

Fig. 2 shows a variant embodiment in which the indicator means is a display device 20 arranged below the dial 16 and visible through an aperture 16a provided in the dial 16.

Display device 20 not only provides an indication of the fact that pressure is being applied, but also provides a value representative of that pressure, which may gradually change as liquid 36 travels through capillary tube 26 and in cooperation with successive sensing elements 40.

Preferably, the depth display device 20 takes the form of a well-known digital display device that includes a liquid crystal cell that displays alphanumeric characters that are also easily readable underwater. Of course the backlight may be turned on for easy reading of the display in low brightness conditions. In the example shown in fig. 1, the displayed information is 5 meters in depth due to the pressure exerted on the pressure measuring device and measured by the pressure sensor 30.

As a variant, the visual indicator device 20 just described may be replaced by or associated with other types of indicators, such as sounders, vibrating devices and/or light emitters. For example, in the example of a diver's watch including a means for illuminating the dial, the illumination means may be turned on automatically once the sensor of the present invention senses that a pressure threshold representing a determined depth has been crossed.

As a known and advantageous way, the circuit 38 can be powered by at least one solar cell 42 suitably arranged on the dial 16 for optimal light reception. The solar cell may provide energy to be stored in an energy storage element (battery, supercapacitor, etc.) to power the circuit even when there is no longer any light on the solar cell 42.

Fig. 3 to 7 show another embodiment of the invention in which pressure sensor 22 is not formed by a timepiece mirror, but is integrated into a timepiece bezel 70. In a known manner, bezel 70 takes the form of a grooved ring arranged on and rotatable relative to the middle part of the timepiece.

Bezel 70 includes an annular housing cavity 72 extending transversely from an upper surface thereof and housing pressure sensor 22 similar to that described with reference to fig. 1 and 2. Pressure sensor 22 includes a reservoir 24 and a capillary tube 26, the reservoir 24 and capillary tube 26 extending in a substantially circular direction and being housed within an enclosed space defined by an upper substrate 74 and a lower substrate 76 that are joined by a sealing frame 78. A circular inner sealing frame 78a and an outer sealing frame 78b are provided over the entire perimeter of the sensor 22 to mechanically stiffen the sensor.

A protective layer 80 and a masking layer 82 are disposed over the upper substrate 74. Masking layer 82 is interrupted in the area above reservoir 24 (fig. 6 and 7). Protective layer 80 includes two holes 84 also disposed above reservoir 24 to allow pressure, e.g., via a liquid, to be applied directly to the portion of upper substrate 74 facing the sensor disposed in reservoir 24 and thus acting (pressure) on substrate 74 at this location.

Thus, as seen in FIG. 7, a blank space 86 is provided in the reservoir region between the upper substrate 74 and the protective layer 80. Spaces 86 and holes 84 allow external pressure to be applied to the entire surface of reservoir 32 and liquid 36 to be driven into capillary 34 in a manner similar to that described in the previous embodiments (fig. 1 and 2).

The above arrangement is particularly illustrated in fig. 5, 6 and 7, where fig. 5 is a cross-section of bezel 70 (taken along line i-i in fig. 4) showing capillary 26, fig. 6 is a cross-section of bezel 70 (taken along line ii-ii in fig. 4) showing one of holes 84, and fig. 7 is a cross-section of bezel 70 (taken along line iii-iii in fig. 4) showing reservoir 24.

As shown more particularly in fig. 3 and 5, a sensing element 40, in this example an indium tin oxide electrode pair 40a, 40b, is disposed on the lower substrate 76 at a suitable location within the area of the capillary 26 and is in contact with the conductive liquid 36 contained within the volume defined by the upper and lower substrates and the sealing frame 78. The electrodes 40a, 40b are connected to a conductive path 88, said conductive path 88 being partially arranged on the lower substrate 76 (fig. 5 and 6) and being connected to a control interface circuit 90 of an indicator device 92 via a zebra connector 94, which zebra connector 94 is arranged in a recess 96 located below the sensor 22. In the embodiment shown, the indicator device is an LED (light emitting diode) visible through the substrates 74, 76 and the protective layer 80. The circuit 90 is powered by a battery 98 (fig. 6).

As described with reference to the embodiment in fig. 1, when the conductive liquid 36 advances in the capillary 26 until it reaches one of the sensing elements 40, the circuit between that sensing element 40 and the conductive path 88 is closed. This passage extends below the lower base plate 76, where it communicates with a printed circuit board that can transmit information to a receiving device (not shown) arranged inside the timepiece. The receiving means may be a pressure value display means as in the example of the first embodiment, or a means for automatically detecting the crossing of a pressure threshold.

In the example shown in fig. 3, the electrodes 40a, 40b of the sensing element 40 are arranged side by side so that only one of the substrates 74, 76 may be processed during manufacturing.

The present invention is not limited to the particular embodiments just described. In particular, when the pressure measurement device is not a timepiece, the pressure sensor may extend in a non-circular direction, for example a substantially linear direction. The electrical energy may be supplied by other sources than batteries or solar cells. The display device may be different from the liquid crystal display.

In particular, the circuit of the pressure measuring device may be independent of the circuit of the timepiece.

In particular, the sensing elements may be distributed differently on one substrate or the other. Similarly, the electrical vias may be disposed on the upper substrate rather than the lower substrate.

Claims (14)

1. A timepiece (2) with a pressure sensor (22), the pressure sensor (22) including a sensing and converting device that senses pressure and converts the pressure into an electrical signal that can be transmitted by an electrical circuit to a control interface circuit of an indicator device, the sensing and converting device comprising:

-an enclosed volume (24, 26) and a liquid (36) contained in the enclosed volume, the liquid (36) being electrically conductive and movable within the enclosed volume (24, 26),

-at least one sensing element (40) arranged at a specified position within the enclosed volume (24, 26), the sensing element (40) comprising at least one pair of electrodes (40a, 40b), and the sensing element (40) cooperating with the liquid (36) when the liquid moves within the enclosed volume (24, 26) such that an electrical circuit is closed when the liquid (36) passes the sensing element (40), and

characterized in that said closed volume (24, 26) comprises a first portion forming a reservoir (24) and a second portion forming a capillary (26), said capillary (26) being arranged along the periphery of said timepiece, said liquid (36) being contained in said reservoir (24) in the absence of pressure and moving from said reservoir (24) into said capillary (26) when subjected to pressure.

2. Timepiece (2) with a pressure sensor (22) according to claim 1, characterised in that the at least one sensing element (40) is arranged along the capillary tube (26).

3. Timepiece (2) with a pressure sensor (22) according to claim 1 or 2, characterised in that the reservoir (24) and the capillary (26) are arranged in sequence in a substantially circular direction.

4. Timepiece (2) with a pressure sensor (22) according to claim 1, characterised in that it comprises a plurality of sensing elements (40) arranged sequentially at a determined distance from each other along the capillary tube (26).

5. Timepiece (2) with a pressure sensor (22) according to claim 1, characterised in that each sensing element (40) comprises a pair of electrodes (40a, 40b) arranged in the same plane.

6. Timepiece (2) with a pressure sensor (22) according to claim 1, further comprising an upper (8a, 74) and a lower (8b, 76) superposed substrate, and a sealing frame (28, 78) joining the two substrates to define the closed volume between them.

7. Timepiece (2) with a pressure sensor (22) according to claim 6, characterised in that each sensing element (40) is carried by one or the other of the upper and lower substrates (8a, 8b, 74, 76).

8. Timepiece (2) with a pressure sensor (22) according to claim 7, characterised in that all the sensing elements (40) are carried by the lower substrate (8b, 76).

9. Timepiece (2) with a pressure sensor (22) according to claim 1, characterized in that the sensing and switching means further comprise an electrical path cooperating with the sensing element (40) and the liquid (36).

10. Timepiece (2) with a pressure sensor (22) according to claim 6, characterised in that the upper substrate (8a) has a smaller thickness than the lower substrate (8b), making it more sensitive when subjected to pressure.

11. Timepiece (2) with a pressure sensor (22) according to claim 1, characterised in that it is provided with a watch mirror (8) inside which the pressure sensor (22) is integrated.

12. Timepiece (2) with a pressure sensor (22) according to claim 11, characterised in that the mirror forms one of the substrates of the pressure sensor.

13. Timepiece (2) with a pressure sensor (22) according to claim 1, characterised in that it is provided with a bezel (70) housing the pressure sensor (22).

14. Timepiece (2) with a pressure sensor (22) according to claim 1, characterised in that the indicator means comprise one or more of a display screen, a vibrating device, a sound generator and a light emitter.