Patent Publication Number: US-6671231-B2

Title: Sequential control method for a display assembly including two superposed display devices

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns a sequential control method for a display assembly including two superposed, respectively top and bottom, display devices, and more particularly a control method for a timepiece including a display assembly of the aforementioned type wherein an analogue display assembly is combined with a digital display assembly. 
     A so-called analogue-digital watch including a combination of analogue and digital display means is already known from European Patent No. 0 078 237 in the name of the Applicant. More precisely, this watch includes analogue time display means including an hour hand and a minute hand. These hour and minute hands are arranged above a liquid crystal display cell which forms a dial for said hands. The cell includes a hole located substantially at its centre, through which a first shaft, onto which the hour hand is fixed and a second shaft onto which the minute hand is fixed, pass. A control circuit applies a control signal across the terminals of liquid crystal display cell so that this cell displays an item of data selected from several types of data, across the terminals of the liquid crystal display cell. It may be, for example, time-related data such as the time, the minute and the second. It may also be date-related data, measured time or other data. 
     Other types of electronic watches including a case inside which are arranged both an analogue display device and a digital display device are also known. This is the case, for example, of a watch having a conventional analogue display device including hands moving above a dial, and a digital display device such as a liquid crystal cell arranged under the dial and visible through an aperture made in said dial. 
     A new type of analogue-digital watch has recently appeared. Such a watch includes a display assembly formed by an analogue display device and a digital display device. The analogue display device includes hour, minute and second hands which move above a dial, while the digital display device includes a liquid crystal display cell arranged in front of the analogue display device which it completely covers. 
     When the digital display device is switched into the state in which it is transparent, the data displayed by the analogue display device is perfectly visible. If, however, one chooses to use the top display device, the latter is then switched into the state in which it is opaque and reflective to totally mask the bottom display device. 
     Thus, when no data is displayed by the digital display device, the watch has the appearance of a conventional analogue device, i.e. the hands and the dial are completely visible through the digital display device which is transparent. Conversely, when data is displayed by the digital display device, the watch has the appearance of a purely digital watch. i.e. the hands and the dial of the analogue display device are totally masked by the digital display device and only the data displayed by the latter is visible. 
     It is thus possible to use either the bottom display device, or the top display device selectively, without one altering the quality and legibility of the data displayed by the other. This constitutes real progress with respect to the analogue-digital watches known to date which simultaneously display analogue data and digital data, consequently making it difficult to read such data, and this is all the more so the greater the density of data displayed. 
     Unfortunately, in the places where these new analogue-digital watches are exhibited in order to be marketed (for example in the window of a retail outlet), there is nothing to distinguish them from conventional analogue watches or digital watches. Indeed, either the top display cell is switched into the state in which it is transparent and in which the dial and the hands of the bottom display device are perfectly visible, and in this case the watch has the appearance of a conventional analogue watch, or the top display cell is switched into the state in which it is opaque and reflective and displays data, and in this case the bottom analogue display device is masked and the watch has a purely digital appearance. Consequently, at first sight there is nothing to enable a potential purchaser or passer-by who may pass in front of the window of the retail outlet to distinguish the analogue-digital watches of the type described above from the purely analogue or purely digital watches and fully appreciate the originality of these new products. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is thus to overcome the aforementioned drawbacks, in addition to others by proposing a control method for an analogue-digital watch of the type defined above which allows a potential purchaser to distinguish such a watch from existing analogue or digital watches at a single glance. 
     The present invention therefore concerns a sequential control method for a display assembly including two superposed, respectively top and bottom, display devices, the top display device including at least a liquid crystal display cell and being arranged so as to be transparent in a first state to make the bottom display device visible, and so as to display a data item and to be opaque and reflective and to mask at least partially the bottom display device in a second state, control means supplying a control voltage to cause the top display device to pass from the first state to the second state and vice versa, this method being characterised in that the display assembly is made to enter an operating state wherein the top display device automatically switches in the state in which it is transparent or into the state in which it is opaque and reflective, so that the display assembly passes alternately from a mode displaying data via the top display device to a mode displaying data via the bottom display device. 
     As a result of these features, a potential client&#39;s attention, stopped in front of the window of a retail outlet or in front of an exhibition stand, is drawn to the originality of the display devices including two superposed display devices by alternately switching the top display device into the state in which it is transparent or into the state in which it is opaque and reflective, so that the display assembly passes automatically from a first data display mode to a second data display mode different to the first. The passer-by&#39;s eye will thus be drawn by this phenomenon, which should make the passer-by interested in the product in question. 
     According to another feature, the present invention concerns a sequential control method for a display assembly formed by an analogue data display device and a digital display device arranged in front of the analogue data display device which it covers at least partially, this method being characterised in that the display assembly is made to enter an operating mode in which the top display device automatically and alternately passes from an analogue data display mode to a digital data display mode. 
     Thus, when no data is displayed by the digital display device, the watch has the appearance of a conventional analogue watch. Conversely, when data is displayed by the digital display device, the watch has the appearance of a purely digital watch. Seeing the watch pass automatically from an analogue appearance to a digital appearance and vice versa, the potential purchaser immediately sees the difference which separates such a watch from conventional purely analogue or digital watches, and may fully appreciate all the advantages which this watch provides from the point of view of the originality of its design, its innovative aesthetic appearance, its ease of use and other advantages. 
     According to another feature of the invention, the top display device and the bottom display device are automatically and alternately activated at a frequency of the order of 0.5 Hz. 
     This frequency is sufficiently high for the flashing phenomenon to be immediately perceptible to the human eye, but nonetheless sufficiently slow for the human eye to be able to distinguish the details of the display in the analogue and digital modes respectively. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will appear more clearly upon reading the following detailed description of an implementation example of the method according to the invention, this example being given purely by way of non-limiting illustration, in conjunction with the annexed drawings in which: 
     FIG. 1 is a cross-section of a wristwatch fitted with a display assembly including two superposed, respectively top and bottom, display devices, the top display device including a double structure formed of a digital display cell arranged above an optical valve, and the bottom display device including analogue time display means formed by a dial above which hands move; 
     FIG. 2 is a cross-section of a wristwatch fitted with a display assembly including two superposed, respectively top and bottom, display devices the top digital display device including a cell arranged so as to be transparent in a first state, and diffusive or reflective in a second state, and the bottom display device including analogue time display means formed by a dial above which hands move; 
     FIG. 3 is a succession of top views of a similar wristwatch to those shown in FIGS. 1 and 2, the top display device being alternately switched into a state in which it is transparent and where the data displayed by the analogue display device is visible, and in a state in which it displays a data item and in which it is reflective and opaque to mask the analogue display device; 
     FIG. 4 is a succession of top views similar to those of FIG. 3 in which intermittently, both the digital display device and the analogue display device are simultaneously visible; and 
     FIG. 5 is a schematic diagram of the electronic circuit necessary to implement the method according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention proceeds from the general inventive idea consisting in controlling the automatic passage of an analogue-digital watch including an analogue display device for time-related data above which is arranged a digital data display device from an analogue display mode of time-related data to a digital display mode and vice versa. This phenomenon of switching on and off digital data giving way, at regular intervals of time, to an analogue display of time data is for the purpose of attracting the attention of the potential client, who passes, for example, in front of the window of a retail outlet, and interesting him in the product in question allowing him to establish immediately the distinction between this type of product and watches which are either exclusively digital or exclusively analogue, or which simultaneously display analogue and digital data. 
     The present invention will be described with reference to a timepiece such as a wristwatch. It goes without saying that the invention is not limited to this application and that it could advantageously be used within the scope of any other application requiring the display of data, such as, for example, measuring instruments. 
     With reference to FIG. 1, a timepiece of the wristwatch type designated as a whole by the reference numeral  1  can be seen. This watch  1  includes, in a conventional manner, a case  2  provided with a back cover  4  in which are arranged an electronic watch movement  6  and a battery  8  which rests on back cover  4  via a contact spring  10 . Movement  6  includes electronic time-keeping circuits associated, via a control circuit, with a drive device (not shown) for a second hand  12 , a minute hand  14  and an hour hand  16  which move above a dial  18 . Case  2  is also closed in a conventional manner by a crystal  20  covering the whole of dial  18 . 
     Watch  1  further includes a display assembly including two superposed, respectively top  22  and bottom  24 , display devices. The display assembly which is fitted to watch  1  will only be described succinctly here as regards its main means. For a more detailed description of this display assembly, reference will advantageously be made to European Patent Application No. 0 926 574 in the name of the Applicant. 
     In the example shown in FIG. 1, bottom display device  24  includes time-related display means, in particular analogue time display means formed by hands  12 ,  14 ,  16  and dial  18 . 
     It goes without saying that this bottom display device  24  could be formed by any digital display device, for example of the liquid crystal type. This bottom display device  24  could also include a combination of analogue and digital display means such as the combination disclosed in the aforecited European Patent No. B-0 078 237 in the name of the Applicant, or a decorative element, for example a picture, figure or other. 
     Top display device  22  includes a double structure formed of a display cell  26  arranged above an optical valve  28 , this top display device  22  extending between bottom display device  24  and crystal  20 . In the example shown, this top display device  22  covers the whole of the surface of dial  18 . 
     Top display device  22  is arranged on the one hand so that display cell  26 , arranged between crystal  20  and optical valve  28 , and the latter are transparent in a first switching state of cell  26  and valve  28 , so as to make the data displayed by bottom display device  24  visible, namely hands  12 ,  14  and  16  and dial  18  in the example shown. 
     On the other hand, top display device  22  is arranged so that display cell  26  display a data item, for example of the alphanumerical type, and so that optical valve  28  is opaque and masks at least partially bottom display device  24  in a second switching state. 
     The switching of display cell  26  and optical valve  28  from the first state to the second state and vice versa is achieved by control means integrated in movement  6 , these control means being connected to cell  26  and valve  28  by means of conventional connectors  30   a ,  30   b  to supply them with a control voltage. 
     According to a particular embodiment, cell  26  is a liquid crystal type display cell. The cell includes a transparent front substrate  32 , a transparent back substrate  34 , a sealing frame  36  forming spacing and closing means and delimiting with substrates  32  and  34  a closed cavity in which there is a layer of liquid crystals. The opposite faces of substrates  32  and  34  include transparent electrodes  38 ,  40 , made for example of indium/tin oxide. In the example illustrated, front substrate  32  carries electrodes configured in digits each formed of segments allowing alphanumerical characters to be displayed, while back substrate  34  carries an electrode extending over its entire surface. Electrodes  38  and  40  are connected to connector  30   a  via contact pads  42  located outside the cavity. 
     When a voltage is applied or removed across electrode  40  and certain of electrodes  38 , the liquid crystals between these electrodes  38 ,  40  are alternately passed from an absorbent state to a transparent state or vice versa, depending on the type of liquid crystals in question and/or the presence and arrangement of polarisers associated with the cell. It is thus possible to display data in a light colour on a dark background or dark data on a light background. 
     In the example shown, display cell  26  is a twisted nematic type liquid crystal cell whose respective external surfaces of substrates  32  and  34  are provided with polarisers (not shown) with crossed orientations. Thus, cell  26  is totally transparent, i.e. in the first switching state, when no voltage is applied across the terminals of its electrodes  38 ,  40  (non-switched state), and is absorbent or diffusing, i.e. in the second switching state, when a voltage is applied across the terminals of its electrodes  38 ,  40  (switched state). 
     It goes without saying that cell  26  may be of another type provided that in a first switching state, cell  26  is transparent, and that in a second switching state, cell  26  is absorbent or diffusing. 
     In the following description, elements identical to those described previously in conjunction with FIG. 1 will be designated by the same reference numerals. 
     With reference to FIG. 2, a timepiece of the wristwatch type is seen, designated as a whole by the general reference numeral  44 . In a similar way to the timepiece previously described, this wristwatch  44  includes a case  2  provided with a back cover  4  occupied by an electronic watch movement  6  and a battery  8 . Battery  8  rests on back cover  4  via a contact spring  10 . Movement  6  is associated with a drive device (not shown) for a second hand  12 , a minute hand  14  and an hour hand  16  which move above a dial  18 . Case  2  is closed in a conventional manner by a crystal  20 . 
     Watch  44  further includes a display assembly including two superposed, respectively top  46  and bottom  48 , display devices. In the example shown, bottom display device  48  includes time-related display means, in particular analogue time display means, formed by hands  12 ,  14 ,  16  and dial  18 . 
     It goes without saying that this bottom display device  48  could be formed by any digital display device, for example of the liquid crystal type. This display device  48  could also include a combination of analogue and digital display means such as the combination described in European Patent No. EP-B-0 078 237 in the name of the Applicant, or a decorative element, for example a picture, a drawing, etc. 
     The display device fitted to watch  44  will only be described succinctly here with respect to its main means. For a more detailed description of this display assembly, reference will advantageously be made to European Patent Application NO. 0 939 331 in the name of the Applicant. 
     According to the invention, top display device  46  includes a display cell  50  and extends between bottom display device  48  and crystal  20 . In the example shown, this top display device  46  covers the whole of the surface of dial  18 . It goes without saying that, according to an alternative embodiment, top display device  46  can form the crystal  20  of watch  44 . Top display  44  is arranged so that display cell  50  is transparent in a first switching state to make the data displayed by bottom display device  48  visible, i.e. hands  12 ,  14 ,  16  and dial  18 . On the other hand, top display device  46  is arranged so that display cell  50  displays a data item, for example of the alphanumerical type, in a second switching state. 
     Switching display cell  50  from the first state to the second state and vice versa is achieved by control means integrated in movement  6 , these control means being connected to cell  50  via conventional connectors  30   a ,  30   b  to supply it with a control voltage. 
     Cell  50  is a liquid crystal display cell of the diffusing or reflective type in the second switching state. 
     According to a particular embodiment, cell  50  is a twisted nematic (TN) type liquid crystal cell. This cell  50  includes a transparent front substrate  52 , a transparent back substrate  54 , and a sealing frame  56  forming spacing and closing means and delimiting with substrates  52  and  54  a closed cavity in which there is a layer of liquid crystals. The opposite faces of substrates  52  and  54  include transparent electrodes  58 ,  60 , made for example of indium/tin oxide. In the example illustrated, front substrate  52  carries electrodes  58  configured in digits each formed of segments allowing alphanumerical characters to be displayed, while back substrate  54  carries an electrode  60  extending over its entire surface. Electrodes  58  and  60  are connected to connector  30   a  via contact pads  42  located outside the cavity. Cell  50  further includes, on the side of crystal  20 , a linear polariser  62  and, on the side of dial  18 , a quarter-wave plate  64  associated with a cholesteric film  66 . 
     It goes without saying that cell  50  may be of another type provided that in a first switching state, cell  50  is transparent, and that in a second switching state, cell  50  is opaque and reflective or diffusing. 
     One thus has a wristwatch  1  or  44  which includes a display assembly formed by an analogue display device and a digital display device. The analogue display device, respectively  24  or  48 , includes a second hand  12 , a minute hand  14  and an hour hand  16  which move above a dial  18 , while the digital display device, respectively  22  or  46 , includes a liquid crystal display cell, respectively  26  or  50 , arranged in front of analogue display device  24  or  48  which it completely covers. 
     When digital display device  22  or  46  is switched into the state in which it is transparent, the data displayed by analogue display device  24  or  48  is perfectly visible. If however, one chooses to use top display device  22  or  46 , the latter is then switched into the state in which it is opaque and reflective to totally mask the bottom display device. 
     Thus, when no data is displayed by the digital display device, the watch has the appearance of a conventional analogue watch, i.e. hands  12 ,  14  and  16  and dial  18  are completely visible through digital display device  22  or  46  which is transparent. Conversely, when data is displayed by digital display device  22  or  46 , the watch has the appearance of a purely digital watch, i.e. hands  12 ,  14  and  16  and dial  18  of analogue display device  24  or  48  are totally masked by digital display device  22  or  46  and only the data displayed by the latter is visible. 
     Watch  1 ,  44  previously described, may thus have, as chosen, a purely digital appearance or a purely analogue appearance, which distinguishes it from watches which are only digital or only analogue, or even from watches which simultaneously display analogue and digital data. 
     However, at first sight, it is impossible to distinguish between a watch as described in the present Patent Application and a conventional watch which is purely analogue or purely digital. Means have therefore been sought to allow a potential purchaser or passer-by who stops, for example, in front of a the window of a retail outlet, to distinguish such a watch from existing analogue or digital watches at first glance. 
     Thus, according to the present invention, a sequential control method is proposed for a display assembly of the type described hereinbefore including a top display device, respectively  22  or  46 , and a bottom display device, respectively  24  or  48 , said method including the step of automatically switching the top display device into the state in which it is transparent or into the state in which it is opaque and reflective, so that the display assembly passes alternately from a first mode displaying data via the top display device to a second mode displaying data via the bottom display device. The passer-by&#39;s eye will thus be drawn by this phenomenon, which should interest him in the product in question. 
     Within the meaning of the present invention, automatic switching means a method in which the watch is made to enter, for example by pressing on a push-button of said watch, an autonomous operating mode requiring no external action on the watch and in which the top display device is alternately switched into a state in which it is transparent or into a state in which it is opaque and reflective, so that the data displayed by the bottom display device appear then disappear cyclically to the observer in order to be replaced by the data displayed by the top display device. 
     When the display assembly is formed by an analogue display device  24  or  48  and a digital data display device  26 ,  28  or  50  arranged in front of the analogue display device which it covers at least partially, the display assembly is automatically and alternately passed from an analogue data display mode to a digital data display mode by alternately switching the digital display device into a state in which it is transparent and in which the analogue data display device is perfectly visible, or into a state in which it is opaque and reflective and in which it displays data by masking the analogue data display device. 
     Thus, upon seeing the watch automatically pass from an analogue data display mode to a digital data display mode and vice versa, the potential purchaser can immediately appreciate the considerable differences which distinguish this watch from conventional purely analogue or purely digital watches. 
     FIG. 3 is a succession of top views of a similar wristwatch to those shown in FIGS. 1 and 2, the top display device  22  or  46  being alternately and automatically switched into a state in which it is transparent and where the time-related data displayed by the analogue display device, respectively  24  or  48  is visible, and into a state in which it displays a digital data item and in which it is reflective and opaque to mask the analogue display device. If the wristwatch shown in FIG. 3 is a watch of the type described with reference to FIG. 1, it includes a double structure formed of display cell  26  arranged above optical valve  28  which are both transparent in a first switching state, so as to make the data displayed by bottom display device  24  visible, whereas display cell  26  displays a data item and optical valve  28  is opaque and masks bottom display device  24  in a second switching state. Conversely, if the wristwatch of FIG. 3 is a watch of the type described with reference to FIG. 2, it includes a single display cell  50  which, as chosen, may be transparent in a first switching state to make the data displayed by bottom display device  48  visible, or display a data item and be opaque and reflective in a second switching state to mask the data displayed by bottom display device  48 . The analogue and digital display sequences follow each other over time at a frequency of the order of 0.5 Hz for example, in the order represented by an arrow in FIG.  3 . 
     FIG. 4 is a succession of top views of a wristwatch similar to those of FIG. 3 in which one can see that digital display device  26 ,  28  or  50  and analogue display device  12 ,  14 ,  16  and  18  are intermittently visible simultaneously, only half, for example, of the digital display device being electrically controlled to display data, while the other half of said digital display device remains transparent so as to make the subjacent analogue time-related data display device visible. Such an operating mode may be activated by the vendor before placing the timepiece in the window or by the user himself if he should wish to give a demonstration to his companions of the extended functions of his watch. Preferably, the analogue and digital display sequences follow each other in time at a frequency of the order of 0.5 Hz which is a sufficiently fast frequency to attract the attention of the potential client examining the contents of a shop window, but also slow enough to allow the observer to appreciate the details of the analogue display and the digital display. 
     FIG. 5 is a schematic diagram of the electronic circuit intended for implementing the method according to the present invention. This Figure shows an electronic time-keeping circuit  68  mounted across the terminals of a quartz oscillator  70 . This time-keeping circuit  68  is conventionally associated, via a frequency divider circuit  72 , for example with a drive device  74  for a motor  76  which supplies the mechanical power necessary to drive hands  12 ,  14  and  16  forming the analogue time-related data display bottom device  24  or  48 . Frequency divider circuit  72  also supplies to control means  78  of top display device  22  or  46  a signal at the desired frequency, for example of 0.5 Hz, so that these control means  78  will apply a control voltage at the same frequency of 0.5 Hz to optical valve  28  or to display cell  50  to cause the latter to pass from a state in which they are transparent and allow bottom display device  24  or  48  to appear, to a state in which they are opaque and reflective to mask said bottom display device  24  or  48  and display alphanumerical type data. 
     It goes without saying that the invention is not limited to the embodiments which have just been described, and that modifications and variants may be envisaged without departing from the scope of the present invention. In particular, it may be envisaged that the wearer himself adjusts the switching frequency at which the top display device becomes alternately opaque to display data and mask the bottom display device, or transparent, thus allowing the bottom display device to appear.