BACKGROUND OF THE INVENTION In the field of digital watches, a certain number of solutions which make it possible to establish an electrical connection between the watch and an external device are already known. Documents US 4,118, 922, US 4,323, 996, US 4,103, 483 and US 4,165, 605 describe for example a certain number of solutions which consist in placing one or more electrical contact elements in the bottom of the casing of the watch, in an area where the watch is in contact with the user's skin, the electrical connection with these contact elements being guaranteed by an adaptor or by suitable contact means.

The proximity of the electrical contact elements of the watch to the user's skin is an important constraint. It is indeed desirable, as a general rule, to avoid all contact of these elements with the user's skin. Mechanical or electrical means of protection must typically be provided in order to limit this risk. On the other hand, these solutions are subject to dirtying or contamination problems which impair the quality of the electrical connection.

More desirable solutions for tackling the problem of a possible contact with the user's skin have already been suggested. The document US 5,703, 460 describes for

example an electrical connection device using a plug-in adaptor which is inserted into a socket provided laterally in the watch casing. Although it allows all contact with the user's skin to be avoided, this solution nonetheless has the disadvantage of only allowing the establishment of an electrical connection with a single contact element (an additional plug-in adaptor being necessary for the establishment of an electrical connection with a supplementary contact element in the watch) and of being more severely subject to contamination problems, dirt and impurities accumulating in the bottom of the socket as the watch is used. Moreover, the configuration of the connection device is not suitable from the viewpoint of guaranteeing the water resistance of the portable instrument.

Another solution using a plug-in adaptor is illustrated by the document JP 2001-186584. This document describes a portable electronic instrument taking the form of a wrist-watch provided with a connection device ensuring an electrical link with a pair of headphones. The plugging-in of the pair of headphones is ensured by a conventional jack-type adaptor. In the context of this application, the adaptor has three electrical contact zones aligned the one behind the other in the direction of insertion of the adaptor into its socket. In the same way, this socket is provided with three electrical contact elements also aligned the one behind the other in the direction of insertion of the adaptor, these three contact elements being electrically linked to the electrical and electronic components housed in the casing of the instrument. It should be noted that the socket into which the adaptor is to be plugged in is not as such arranged directly in the casing of the instrument, but into an additional casing attached to the casing of the instrument, the electrical connection between the two casings being ensured by components of a similar construction to that of a push-button.

This solution has the advantage of requiring only a single plug-in connector to establish a plurality of electrical connections, as well as constituting a relatively widespread standard on the market. This solution is however always ill-adapted with regard to the sealing constraints of the portable instrument and is also very sensitive to the build-up of dirt or impurities which may impair the quality of the electrical contact. Moreover, the construction of such a device remains relatively complex and is not very robust in use.

SUMMARY OF THE INVENTION The aim of the present invention is to propose a solution of simple and robust construction which is particularly adapted to the construction constraints of a portable

electronic instrument intended to be used in various environments where the accumulation of dirt and of impurities constitutes a problem.

The present invention has furthermore the aim of proposing a solution which allows the water resistance of the portable electronic instrument to be readily ensured.

A further aim of the present invention is to propose a solution which makes it possible to guarantee a high quality of electrical contact between the portable instrument and the plug-in adaptor.

Yet another aim of the present invention is to propose a solution which may be particularly suited for use within the framework of a battery recharging system The present invention has thus as its main object a device providing an electrical connection between a portable electronic instrument and an external device the features of which are set down in the independent claim 1.

The present invention also has as object a battery recharging system for a portable electronic instrument using such an electrical connection device.

Finally the present invention also has as object a plug-in adaptor used in the framework of the above-mentioned electrical connection device.

Advantageous embodiments of the present invention are the subject of the dependent claims.

According to the proposed solution, the electrical contact elements arranged in the socket into which the plug-in adaptor is inserted are disposed substantially perpendicularly to the direction of insertion of the adaptor. The adaptor for its part comprises electrical contact zones each intended to come into contact with a corresponding electrical contact in the socket and extending side by side substantially parallel to the direction of insertion of the adaptor in the socket. It will be understood thus that the contact elements arranged in the socket and the corresponding contact zones provided on the adaptor do not face one another, but cooperate perpendicularly.

This respective arrangement of the electrical contact elements and the electrical contact zones has the advantage of great simplicity and great robustness in use. As will be seen in detail in the remainder of the description, the arrangement of the electrical contact elements in the portable instrument may very easily be achieved at the same time as ensuring an adequate water resistance of the instrument at this level.

Preferably, the arrangement of the contact elements and the contact zones in relation to one another is selected such that, during the insertion of the adaptor, the

contact elements exert friction on the corresponding contact zone. In this way self- cleaning of the electrical contacts takes place facilitating a high quality of contact.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the present invention will become more apparent by reading the detailed description which follows of a preferred embodiment of the invention given solely by way of non-restrictive example and illustrated by the annexed drawings in which: - Figure 1 shows a plan view of a portable electronic instrument in the form of a wrist-watch, as well as of a plug-in adaptor inserted in a socket of the portable instrument to ensure an electrical connection of this instrument with an external device not illustrated, this arrangement illustrating an embodiment of the present invention; - Figure 2 is a partial view taken in the 9 o'clock position of the portable electronic instrument of Figure 1 showing the socket intended to receive the plug-in adaptor, two electrical contact elements the ends of which are shown being arranged inside this socket; - Figures 3a and 3b are perspective views, respectively of the upper and lower sides, of the plug-in adaptor of Figure 1; - Figure 4 is a partial sectional view of the portable instrument and of the plug-in adaptor of Figure 1 taken on a cutting plane parallel to the direction of insertion of the plug-in adaptor and passing through one of the electrical contact elements illustrated in Figure 2; - Figure 5 is a partial sectional view of the portable instrument and of the plug-in adaptor of Figure 1 taken on a cutting plane perpendicular to the direction of insertion of the plug-in adaptor and passing through the electrical contact elements represented in Figure 2; and - Figure 6 is a perspective view of the lower face of the portable electronic instrument, with the plug-in adaptor mounted, illustrating a snap-lock mechanism of the adaptor in the socket of the portable instrument.

EMBODIMENTS OF THE INVENTION The Figures show one embodiment of a device for establishing an electrical connection between a portable electronic instrument and an external device using a plug-in adaptor according to the invention. It will be understood that the invention is

not limited to this single embodiment but may be applied to all types of portable electronic instrument, which may be in the form of a wrist-watch as illustrated or in the form of any other portable instrument (mobile telephone, pocket calculator, electronic organiser, personal digital assistant, etc.).

It will also be understood that the nature of the external device which is to be connected electrically to the portable electronic instrument has only little importance. It could be for instance, in accordance with what will be discussed below, a device for recharging the battery of the portable instrument or of any other device requiring an electrical link with the portable instrument. Thus, the plug-in adaptor could be used to connect a peripheral to the portable instrument (for example a pair of headphones, an external interface for non-contact communication-RF-type, optical, inductive,..., etc. ) or to connect the portable instrument to a computer terminal or another portable instrument. Generally speaking, the device for establishing electrical connection according to the invention may be used to pass electrical signals or data.

Figure 1 shows a plan view of a portable electronic instrument designated globally by the reference numeral 1 and taking the form of a wrist-watch, to which an external device (not illustrated) is linked by means of a plug-in adaptor, designated globally by the reference numeral 2, which is inserted in the direction A into a socket 15 of the portable instrument 1. As illustrated in Figure 2, the socket 15 into which the plug-in adaptor 2 is inserted is provided in a part forming the bottom 11 of the casing 10 of the portable instrument 1.

In the example illustrated, two electrical contact elements 31,32 emerge in the socket 15 (only the ends of the elements 31,32 being visible on Figure 2). These contact elements 31,32 are intended to come into contact with the corresponding electrical contact zones, designated respectively 21 and 22, provided on an extension 25 of the adaptor 2. In this embodiment, contact elements 31,32 are aligned in a plane which is substantially perpendicular to the direction of insertion A of the plug-in adaptor 2. The contact elements 31,32 could alternatively be offset with respect to the direction of insertion A.

According to the preferred embodiment illustrated in Figures 1 and 2, it will be noted that the portable electronic instrument 1 is adapted to be worn in contact with the user's skin (in this case in contact with the wrist), the lower face 11 a of the bottom 11 of the portable instrument thus constituting an area of contact with the skin.

Because of the proximity of the skin, the socket 15 is preferably provided in the bottom 11 recessed with respect to the zone of contact 11 a of this bottom with the user's skin. On the other hand, the electrical contact elements 31,32 extend into the

socket 15 in the direction of the contact zone 11 a but without being able to come into contact with the user's skin.

Figures 3a and 3b illustrate in greater detail the structure of the plug-in adaptor 2. The latter consists essentially of a body 20, constructed here of two assembled portions 20a and 20b, and of an extension 25 disappearing for the most part in the socket 15 after insertion in the portable instrument 1. The body 20 is linked to the external device, not illustrated, by means of a cable comprising two conductors in this example. On this account, it will be understood that the number of contact elements, of contact zones and of conductors obviously depends on the nature of the external device and/or on the nature of the electrical signals to be transmitted. As an example of application, the adaptor 2 is here used to connect the portable instrument 1 to an external device for recharging batteries and requires in this case a pair of connection lines to connect the portable instrument 1 and its battery, not illustrated, to the recharging system. Alternatively, more than two connection lines might be provided.

The electrical contact zones 21,22 take the form of a pair of conducting tongues arranged side by side substantially in the same plane. A portion of these conducting tongues is exposed on the upper face of the extension 25, that is to say the face of extension 25 which is directed towards the electrical contact elements 31,32 during the insertion of the plug-in adaptor 2 into the socket 15 of the portable instrument 1.

The other face of extension 25 (the lower face) has a rib 25a intended to cooperate with a corresponding opening 15a in the wall of the socket 15. This lateral opening 15a is more clearly visible in Figures 4 to 6. The rib 25a includes moreover a protuberance, designated 25b, which plays a part in the mechanical locking of the adaptor 2 in the socket 15 of the portable instrument, as will be seen in more detail with reference to Figure 6.

Figures 4 and 5 illustrate more clearly the manner in which the adaptor 2 is arranged after insertion into the socket 15 of the portable instrument as well as the manner in which the contact elements 31,32 and the contact zones 21,22 cooperate.

Figure 4 is a partial sectional view of the portable instrument 1 and of the adaptor 2 along a cutting plane parallel to the direction of insertion A of the adaptor 2, and passing through the contact element 31. Figure 5 is a partial sectional view of the portable instrument 1 and of the adaptor 2 along a cutting plane perpendicular to the direction of insertion A and passing through the contact elements 31 and 32.

As can be seen in greater detail in Figures 4 and 5, each contact element 31,32 takes the form of a moveable conductive stem (similar in configuration to the stem of a push-button) mounted vertically, top towards the bottom, in the bottom 11 of the

casing 10. Each contact element 31,32 is thus mounted in a corresponding opening 41,42 provided in the bottom 11 and opening into the upper wall of the socket 15. It should be noted that each contact element 31,32 is held in its opening 41,42 by means of a collar provided at the base of its head and which is able to come to rest, as is illustrated in Figures 4 and 6, on a narrowing in the opening. This narrowing thus ensures the retention of each contact element. It is to be noted that this narrowing is configured so as to deform in a resilient manner during mounting of the contact elements 31,32 in casing 10.

The water resistance of the portable instrument 1, at the level of the socket 15 and of the openings 41,42 is ensured by a pair of O-ring joints 35,36 arranged in a groove provided on the contact elements 31,32.

It will be noted also that each contact element 31,32 is firmly attached to a spring element 33,34 respectively, which conditions their axial displacement. These spring elements 33 and 34 are placed between the contact elements 31,32 and a printed circuit board (hereinafter referred to as PCB) 50 bearing two contact areas 51, 52 connected electrically to the spring elements 33,34. This PCB 50 rests for its part in the casing 10 of the portable instrument as illustrated in Figure 4.

In the rest position, as illustrated partially in Figure 2, the spring elements 33 and 34 cause a slight vertical displacement of the contact elements 31,32 towards the bottom. During insertion of the plug-in adaptor 2, the contact elements 31 and 32 are pushed upwards in the direction of PCB 50, compressing the spring elements 33 and 34, under the effect of the conducting tongues 21,22. As illustrated in Figures 3a and 4, the ends 21 a and 22a of the conducting tongues 21,22 are curved downwards to facilitate the insertion of the tongues and to avoid becoming jammed.

In the light of Figures 4 and 5, it will be understood that during the insertion of the plug-in adaptor 2 into the socket 15, each contact element 31,32 will exert friction on the corresponding electrical contact zone 21,22. This friction is preferable from the point of view of the quality of electrical contact because it ensures self-cleaning of the contact region.

As has already been mentioned above, according to the preferred embodiment, the socket 15 has, besides its front opening allowing the insertion of the plug-in adaptor 2, a lateral opening 15a in the lower wall of the socket 15. This opening 15a facilitates, on the one hand, cleaning of the ends of the contact elements 31 and 32, the latter being partially accessible through this opening 15a. On the other hand, as illustrated in Figures 4 and 5 (as well as in Figure 6), the lateral opening 15a receives the rib 25a formed on the extension 25 of the adaptor 2 and thus plays the role of a

foolproof mechanism, that is to say a mechanism for ensuring that the adaptor 2 can only be inserted into the socket 15 in a single manner as will be understood readily from the illustration of Figure 5.

By preference, as has already been mentioned and illustrated in Figure 6, the rib 25a on the adaptor 2 is also provided with a protuberance 25b which is intended to retain the adaptor 2 mechanically in the socket 15 once inserted. The opening 15a has therefore an enlargement 15b to receive this protuberance 25b. It will have been understood that the rib 25a, the protuberance 25b, the opening 15a and the enlargement 15a cooperate to form a snap-lock mechanism for the adaptor 2 in the socket 15. It will also be understood that other snap-lock mechanisms could be envisaged, the adaptor 2 being able for example to be locked in the socket by means of a mechanism placed on the front portion of the socket 15. In the same way, the foolproof function of the opening 15a and of the rib 25a could be achieved differently, for example by means of a rib formed on one of the lateral portions of the extension 25 and of a corresponding groove in one of the lateral walls (vertical walls in Figure 5) of the socket 15. It will be noted nevertheless that the lateral opening 15a is preferable however, as already mentioned, in order to facilitate cleaning of the ends of the contact elements 31 and 32.

By way of advantageous modification, it may be wise to provide the bottom of the socket 15 with a switching mechanism permitting the electrical uncoupling of the contact elements 31 and 32 from the electrical and/or electronic components to which they ought to be linked when the plug-in adaptor 2 is not inserted. This switching mechanism may, as far as its mechanical and electrical parts are concerned, take the form of a push-button, the axial displacement of which would be initiated by the end portion of the extension 25 and which, once displaced by the presence of the adaptor 2, would lead to the closing of an electrical circuit interposed between the contact elements 31 and 32 and the associated electrical and/or electronic components.

By way of supplementary modification, the provision of a mechanism to vertically displace the contact elements 31,32 only after the insertion of the adaptor 2 could be easily envisaged. This could be effected by means of a cam mechanism similar to that which is encountered in crown-stem mechanisms in order to follow their axial displacement, the displacement of the cam being produced mechanically by the presence of the adaptor 2 in the socket 15. According to this modification, it will be understood that the contact elements 31,32 could be arranged in such a way that they do not necessarily exert friction on the contact zones 21,22 of the adaptor. This

friction remains nonetheless preferable from the point of view of guaranteeing the good quality of the electrical contact.

It will be generally understood that various modifications and/or obvious improvements for the person skilled in the art can be made to the embodiment described in the present description without departing from the framework of the invention defined by the annexed claims. In particular, the present invention is not limited solely to a use in a wrist-watch and is obviously not limited to a connection device employing only two electrical connection lines.

One modification could for instance consist in providing the plug-in adaptor with additional contact zones and providing the socket with additional contact elements. In particular, the plug-in adaptor might be provided with four distinct contact zones (for example through the provision of four conductive tongues on the upper and/or lower part of the plug-in adaptor) arranged in any suitable manner so as to respectively contact four electrical contact. elements disposed in the socket. In this case, two contacts could be used to perform a recharging operation while the other two could be used to exchange data. The four contact zones could either be arranged side by side on the plug-in adaptor or could be arranged by pairs in two separate planes so that the plug-in adaptor can be constructed as a more compact unit. Similarly, the four contact elements could be aligned in a same plane (as this is the case for contact elements 31,32 in the Figures) or be arranged in a 2 x 2 configuration in two separate planes. Additional contact zones might also be arranged laterally on each side of the adaptor and corresponding contact elements be provided in the casing with a horizontal orientation.