EP1094373B1 - Electroluminescent device for dial illumination - Google Patents

Abstract

A watchcase (1) has battery compartment and battery(5,6), an electronic circuit delivering pulses (15), hands (12) and watchglass (4). The watch dial is illuminated by an electroluminescent ring which is secured to the watchglass heel (17) by a pressed fit translucent ring (19) and has tabs which make contact with elastic electrical connections (33,34) from the pulsing circuit

Description

The present invention relates to a light-emitting device for illuminating a dial, and more particularly to the circular dial of a small-sized device with an autonomous energy source, such as a timepiece to enable night reading. hourly indices located on the periphery.

The use of electroluminescent sheets to illuminate a dial at night is well known. In the document US 4,775,964 a electroluminescent sheet is cut to the dimensions of the dial of a wristwatch, pierced with a hole in its center for the passage of the axis of the needles, provided with hourly indices by printing or screen printing on the side facing the observer and connected, by flexible connectors welded to each electrode of the electroluminescent sheet, to an electronic circuit provided to provide an appropriate pulsed voltage. The improvements described in the document US5,265,071 essentially concern the simplification of the connection means which are then formed by a tongue, curved or not, and a bare electrode portion is coated with a conductive ink to avoid or compensate for possible cracking of the electrode to establish at least one contact with the printed circuit. Such a construction offers the advantage of being relatively simple to implement. However, it has the drawbacks of having a still high energy consumption, due to the importance of the surface covered, despite the progress made in the design of electroluminescent sheets and excitation circuits, and to restrict the possible aesthetic variations in the dial, variations that are often desired by manufacturers to differentiate their products from those of competitors.

To reduce the energy consumption it is naturally possible to reduce the surface of the electroluminescent sheet for example by limiting its area to the contour of the hourly indices, as described in document DE 4,023,693 , or on the contrary by cutting into its surface openings representing said hourly indices, as described in the document JP-A-02-177290 , which complicates the assembly of electroluminescent elements on the dial. On the other hand, to have a certain aesthetic effect it has also been proposed to use several electroluminescent sheets of different colors, for example cut into sectors or in concentric rings, as described in the document JP-A-05-182761 . Here again the construction, and especially the connection, becomes complicated and the aesthetic variations remain limited.

In fact, to have the greatest possible freedom in the decoration of the dial, both in daytime observation and night observation, it is better to have indirect lighting from the flange.

Many devices using one or more diodes, associated or not with a light guide have been proposed. As an example we can mention the documents US 4,705,407 ; US 4,908,739 or EP 0 860 755 which disclose different shapes or structures of PMMA rigid annular guides for optimally focusing the light on the dial and providing uniform illumination. It turns out however to use that it is very difficult, if not impossible to have a truly uniform illumination.

The object of the invention is to overcome the disadvantages of the aforementioned prior art by providing a lighting device by means of a strip-shaped electroluminescent lamp easy to set up and connect to the excitation circuit.

For this purpose the invention relates to a small device comprising a housing in which are housed a movement driving at least one needle facing a scale of a dial, a power source and an electronic circuit capable of supplying a pulsating voltage, said casing being closed by a prolonged dial-side mirror by an annular extension forming a flange, characterized in that a circular clearance is provided inside the base of the flange to receive on the one hand a light-emitting ring formed of a strip having a strip extending beyond the base and a connecting tab, on the other hand a ring of a translucent plastic material mounted in force in the annular clearance to hold the electroluminescent ring at the bottom of the this one.

• la figure 1 est une vue de dessus d'une montre-chronographe,
• la figure 2 est une vue en coupe selon la ligne II-II de la figure 1,
• la figure 3 est une vue agrandie de la zone de contact de l'anneau électroluminescent selon la flèche III de la figure 2,
• la figure 4 est une vue agrandie de l'assemblage de l'anneau électroluminescent en un point quelconque de son pourtour,
• la figure 5 représente en perspective agrandie la portion de l'anneau électroluminescent au niveau de la patte de connexion, et
• la figure 6 est une représentation en perspective éclatée, montrant le procédé d'assemblage du dispositif d'illumination dans une montre.

Other characteristics and advantages of the invention will appear on reading the description of an exemplary chronograph watch, with reference to the appended drawings in which:

• the figure 1 is a top view of a chronograph watch,
• the figure 2 is a sectional view along line II-II of the figure 1 ,
• the figure 3 is an enlarged view of the contact zone of the electroluminescent ring according to the arrow III of the figure 2 ,
• the figure 4 is an enlarged view of the assembly of the electroluminescent ring at any point of its periphery,
• the figure 5 represents in enlarged perspective the portion of the electroluminescent ring at the connection lug, and
• the figure 6 is an exploded perspective representation showing the method of assembling the illumination device in a watch.

Referring to figures 1 and 2 , there is shown a chronograph watch which comprises conventionally a casing formed by a housing 1, comprising a bottom 2 and a middle part 3 in one piece, closed at its upper part by an ice 4.

The bottom comprises a hatch 5 to replace the energy source 6 constituted by a button cell.

The caseband comprises a crown 7 and two pushbuttons 8, 9 serving in a conventional manner for setting the time and the chronograph operation, and a third pushbutton 10 for activating the illumination device for night reading Of time. It is obvious that for a watch without chronograph function it would be enough to have a crown and a single push-button, or even just a push-button knowing that there are mechanisms to perform both functions by means of a single control member. Inside the case there is a chronograph movement 14 for driving the needles at the center 12a, 12b, 12c and the counter hands 13a, 13b, 13c, above a dial 11.

Preferably the chronograph movement is an electronic movement powered by the button cell.

The housing 1 also contains an electronic circuit 15 connected to both the energy source 6 and flanges 33, 34 which will make it possible to establish contact with a light-emitting ring 20 by simple assembly.

Referring to Figures 2 to 4 and 6 it can be seen that the curved glass 4 has in its portion facing the dial an annular extension forming a flange 17. The flange 17 comprises at its base 18 a small annular shoulder 16 and a substantially rectangular annular clearance 19 and open towards the inside the case 1.

The annular clearance 19 comprises against its wall 19a, and all around its periphery, an electroluminescent ring 20 and a ring 30. The ring 20 is obtained by cutting in a light-emitting sheet, such as those available on the market from the company Lumitec (Gais-Switzerland), a strip having substantially the length of the perimeter 19, measured at its wall 19a. The width of this band must be slightly greater than the height of the clearance 19 to form a small strip 21 whose function will be explained later. At any point in the ring 20, there is provided a tab 22 perpendicular to the strip to enable the connection to be made. In the example shown, this lug 22 is arranged at 1/4 of the length, so as to be able to establish the electrical connection to the 9 o'clock position, where there is no crown or push button, and to have the joining the two ends of the band at the 6h position, which is the least visible in the case of a wristwatch.

This tab 22, shown in more detail at figure 5 , has two contact areas 23, 24 formed by the conductive tracks of the electroluminescent sheet. These contact zones 23, 24 are made during the manufacture of a light-emitting sheet, comprising a plurality of imprints having the developed form of the ring 20, removing at the tabs 22 of the structuring steps.

On the figure 5 it will also be observed that by bending the ring-shaped strip, the lug 22 is stiffened, but with a large radius of curvature that does not risk damaging the contact zones 23, 24, and therefore without being necessary to protect them with a conductive paint.

After setting up the ring 20 having previously returned the ice 4, operation represented by the arrow 1 on the figure 6 , it is blocked by means of the ring 30 of translucent plastic material, operation represented by the arrow 2. To facilitate this implementation, particularly in the case of automation of assembly operations, the ring 30 initially has a preform oval, and in the example shown a rectangular section. With particular reference to Figures 3 and 4 it can be seen that the thickness of the ring 30 is such that it is flush with the angle of junction with the window 4 and that its height is slightly smaller than the depth of the annular recess 19.

Once the ring 20 is blocked by the ring 30, the ice can be manipulated and returned to adjust it to the casing 1, operation represented by the arrow 3 on the figure 6 .

As we see on the Figures 3, 4 and 6 between the dial 11 and the inner wall 26 of the caseband 3 there is provided a circular passage 27 in which will engage the small annular shoulder 16 of the ice, the strip 21 of the ring 20, and the connecting lug 22 whose contact zones 23, 24 will engage between contact flanges 33, 34 connected to the electronic circuit 15 provided for delivering a pulsed voltage when exerting a pressure on the pusher 10.

The construction according to the invention which has just been described is therefore easy to implement and can be adapted by those skilled in the art to a large number of products without departing from the scope of the invention defined by the claims. . It has the advantage of allowing the utmost freedom for decoration and, by the choice of the electroluminescent sheet and the pulsed voltage, to make it possible to vary the color and the lighting zone from the width of the ring where the hourly indices are arranged up to the entire dial.

Claims (6)

1. Apparatus of small dimensions including a case (1) in which are housed a movement (14) driving at least one hand (12a, 12b, 12c) with respect to the scale of a dial (11), a power source (6) and an electronic circuit (15) able to supply a pulsed voltage, said case being closed by a crystal (4) extended on the dial side by an annular extension forming a flange (17), characterised in that a circular recess (19) is provided inside the base (18) of the flange (17) to accommodate on the one hand, an electroluminescent ring (20) formed of a strip having a border (21) extending beyond the base and a connecting lug (22), and on the other hand a ring (30) made of translucent plastic material forced into the annular recess (19) to hold the electroluminescent ring (20) at the bottom thereof.
2. Apparatus of small dimensions according to claim 1, characterised in that the holding ring (30) has an oval pre-shape so as to facilitate the setting in place thereof.
3. Apparatus of small dimensions according to claim 2, characterised in that the holding ring (30) has a regular rectangular cross-section the height of which is less than the depth of the annular recess.
4. Apparatus of small dimensions according to claim 1, characterised in that the translucent plastic material forming the holding ring (30) is for example polymethylmethacrylate (PMMA).
5. Apparatus of small dimensions according to claim 1, characterised in that dial (11) has a surface having the same contour as that of the bottom of the annular recess (19), reduced by a value equal to the thickness of the electroluminescent ring (20) so as to arrange a passage (27) for the connecting lug (22) towards elastic contact strips (33, 34) connected to the electronic circuit (15) and to grip the border (21) onto the periphery against the wall (18a) of the annular recess.
6. Apparatus of small dimensions according to any of claims 1 to 5, characterised in that the apparatus of small dimensions is a timepiece in which the movement (14) drives the hands with respect to the scale corresponding to the time symbols.

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