CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to European Patent Application No. 18173871.7 filed on May 23, 2018, the entire disclosure of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention concerns a watch comprising a watch case provided with a case middle, wherein the case middle carries an element provided with at least one illuminable index.

The watch is configured to be able to be immersed in seawater, such as, for example, a diver's watch.

BACKGROUND OF THE INVENTION

In the field of watches having a watch case provided with a case middle, it is known to arrange on the case middle an element provided with at least one illuminable index. In the case of a diver's watch, the element is, for example, a rotating bezel and the index, for example, indicates a reference position for the diver to measure his immersion time in the ocean. To achieve this, the diver rotates the bezel so as to align the index with the minute hand. This position then becomes the reference for measuring elapsed time. One of the main efficiency criteria of a diver's watch must be the legibility of the time and of the index during the immersion phase.

In order to meet this criterion, a known solution consists in coating the bezel index and the watch hands with a phosphorescent material. This makes the index and the hands visible in low lighting conditions, typically several metres underwater. Such a diver's watch is, for example, described in French Patent Application No. FR1572837A. However, a drawback of this solution is that it requires charging the phosphorescent elements in advance with sunlight or with an artificial light source, so that said elements can then emit light, for a duration limited to several hours and in a decreasing manner (type of phosphorus, quantity, charge duration and intensity prior to diving), in a dark environment, for example underwater.

Wristwatches having a dial provided with several luminous indices are also known, allowing information on the dial to be read in the dark as well as in broad daylight.

Such a wristwatch is, for example, disclosed in WO Patent Application No. 2016146350 A1. The wristwatch includes a watch case, a rotating bezel mounted on the watch case and a dial provided with several luminous indices. The luminous indices are illuminated through the dial by a light source disposed underneath the dial and powered by an electrical energy source such as a cell or rechargeable storage battery. A light source activation component is housed inside the rotating bezel and cooperates with a detection component housed inside the watch case. Thus, the user can switch on the light source by pivoting the rotating bezel and moving it into a predetermined position in which the presence of the activation component is detected by the detection component which, in response, switches on the light source; here, the bezel acts like a switch. However, when the electrical energy source runs out, it must be replaced or manually charged again, which is restrictive for the user.

SUMMARY OF THE INVENTION

It is thus an object of the invention to provide a watch allowing the index to be illuminated in low lighting conditions, especially underwater, yet which is simple to use and does not require phosphorescent elements to be charged in advance or an electrical energy source to be replaced or manual charged.

To this end, the invention concerns a watch, which includes the features mentioned in the independent claim1.

Specific embodiments of the watch are defined in the dependent claims2to20.

One advantage of this watch according to the invention lies in the use of a pair of electrodes fixed inside an inner cavity of the element and a light source device connected to the pair of electrodes and arranged opposite the index. The element is water permeable so that, when the watch is immersed in seawater, seawater can penetrate the inner cavity. The pair of electrodes and the seawater thus form an electrochemical cell. Thus, when the watch is immersed, seawater enters the space between the electrodes, thereby switching on the battery thus formed and powering the light source device. This offers a particularly simple solution for illuminating the index in low lighting conditions underwater, without requiring an operation to replace or manually charge an electrical energy source. Further, the index is illuminated and remains illuminated as soon as the watch is immersed, without the user having to press any particular buttons or control members.

According to a preferred embodiment of the invention, the element is an annular bezel rotatably mounted around the case middle, the bezel defining an inner cavity leading to the exterior of the watch case. The electrode pair and the light source device are preferably integral with the annular bezel so as to rotate around the case middle at the same time as the bezel.

Advantageously, the watch further includes a mechanical element for separating the two electrodes of the pair of electrodes. This prevents any physical contact between the electrodes.

Advantageously, the watch includes several pairs of electrodes of opposite polarity, the electrode pairs being series connected to each other. Thus, for example, when the light source device includes at least one light emitting diode, the diode threshold voltage is reached more quickly to switch it on.

According to a particular technical feature of the invention, the light source device includes at least one light emitting diode.

Advantageously, the light emitting diode is coated with a protective resin able to electrically isolate the light emitting diode from water. This protects and electrically isolates the light emitting diode from water.

Also advantageously, the light emitting diode is arranged inside the inner cavity of the element, underneath the index. This particularly configuration allows efficient illumination of the index when the watch is immersed in seawater.

According to a particular technical feature, the index is formed of an aperture arranged in the element, said aperture being provided with a window able to let in light. Preferably, the window is made of a sapphire glass.

Advantageously, at least one of the free surfaces of the sapphire glass is frosted. This diffuses the light emitted by the light source device better and increases the angle of view of the illuminated index.

According to a particular embodiment of the invention, the electrodes of the electrode pair are selected such that the electrode pair and seawater form a Leclanché type electrochemical cell. This particular example embodiment has the advantage of obtaining improved electric power for the electrochemical cell.

According to another particular example embodiment of the invention, the electrodes of the electrode pair are selected such that the electrode pair and the seawater form a metal-air electrochemical cell. This example embodiment has the advantage of obtaining high energy density for the electrochemical cell.

Advantageously, one anode of the electrode pair is formed of a metal material chosen from the group consisting of aluminium, zinc and magnesium. Such materials have the advantage of being very energetic.

Thus, if the cell dries quickly and thus becomes inactive between two successive immersions, corrosion of the anode will not have time to significantly affect the galvanic performance of the cell.

Advantageously, an inner wall of the inner cavity is coated with a layer of a water soluble salt. This offers the advantage of also allowing the watch to be used in a fresh water environment. Indeed, the salt, combined with the fresh water in which it dissolves, then forms an electrochemical cell with the electrode pair.

Advantageously, the watch also includes an external actuator and an additional light source arranged inside the watch case facing a dial of the watch, the external actuator and the additional light source being connected to the electrode pair. Thus, through contact on the electrodes via actuation of the external actuator, it is also possible to power the additional light source, and thus to illuminate not only the index but also the watch dial and hands.

