Abstract:
Push button for a timepiece for correcting the time display associated with a decompression valve within a single control device. It essentially includes a first push button return spring ( 10 ) followed by a second spring ( 13 ) arranged to bend and act as a valve spring.

Description:
This application claims priority from European Patent Application No. 12175537.5 filed Sep. 7, 2012, the entire disclosure of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a push button for a timepiece including a cylindrical armature inside which there is a longitudinally-arranged through push button (respectively a corrector) formed of a head, having a bottom face abutting against a first shoulder made in the armature when manual pressure is exerted on the head, and a stem ending in a screw limiting the axial travel of the stem in the armature. A first return spring of the push button is wound about the stem. 
     BACKGROUND OF THE INVENTION 
     Push buttons conforming to the above description are well known in the state of the art. They are, for example, fitted to chronographs or wristwatches for correcting, for example, the date. They are called “push buttons” when they protrude from the middle part and correct a function when pressed with a finger. When the pressure ceases, the push buttons return to their initial position. They are usually called “correctors” when they are embedded in the middle part of the watch. In principle, each push button is linked to the correction of a single function; thus where there is a plurality of functions to be corrected, a plurality of push buttons must be fitted to the middle part of the timepiece, which then weakens the sealing of said timepiece. 
     The idea of the present invention is to give a conventional push button an additional function, to avoid further piercing the timepiece. The additional function may consist of a valve fitted to a diver&#39;s watch. 
     For the reasons set out above, CH Patent Application No 699 558 A1 has already proposed a screw-in winding crown associated either with a push button, or with a valve in a single control device. There is no description or suggestion of a combined push button-valve. 
     As is well described in the aforecited document, diver&#39;s watches often include both a winding crown and a valve to prevent the watch exploding when the diver returns to the surface. Indeed, as explained in said document, professional divers descend to great depths to carry out work and are then returned to the surface using a pressurised chamber which controls the decompression stops required for the diver&#39;s health. During these decompression stops, gases—essentially helium—penetrate the divers&#39; watch case through the sealing gaskets which are essentially suited to preventing water or dust from entering inside the watch. When the pressure in the chamber drops during decompression stops, if there is no pressure balance device in the watch, excess pressure may build up inside the watch relative to the surrounding pressure, which may cause the watch to explode. In diver&#39;s watches, a valve is arranged separately from the other controls for the pressure balance. However, this valve suffers from the same drawbacks as those affecting push buttons or crowns with respect to sealing problems. 
     SUMMARY OF THE INVENTION 
     To avoid the aforecited drawback, the present invention proposes a push button conforming to the definition given in the first paragraph of this description, further characterized in that a second spring, placed after said first spring, is wound around the stem; one end of said second spring rests on said first retaining means and the other end rests on a second retaining means of said armature. The second spring is calibrated to a force matching the compensating pressure to bend and act as a valve if the pressure inside the timepiece is higher than the pressure prevailing outside said timepiece. 
     The features and advantages of the present invention will appear from the following description, given with reference to the annexed drawings, and providing, by way of explanatory, but non-limiting example, two advantageous embodiments of the invention. In the drawings: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 to 3  are plan and cross-sectional views of a first embodiment of the push button-valve according to the present invention. 
         FIG. 4  is an alternative embodiment of the push button-valve shown in  FIGS. 1 and 3 . 
         FIGS. 5 and 6  are plan and cross-sectional views of a second embodiment of the push button-valve according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the first embodiment shown in  FIGS. 1 to 3 , the push button includes a cylindrical armature  50  inside which there is a longitudinally-arranged through push button  51  formed of a head  9 , having a bottom face  11  abutting against a first shoulder  52  made in armature  50  when manual pressure is exerted on head  9 . Cylindrical armature  50  is in two parts; the first part is formed of a tube  7  fixed in the middle part of the timepiece. Here, tube  7  is screwed into the middle part of the timepiece via the bottom tube portion  81  and in the median tube portion has a bulge  82  provided with a groove housing an O-ring joint  83  sealing the tube at the level of the case. Tube  7  ends in a top tube portion  56  which protrudes from the middle part of the timepiece. This protruding portion  56  is provided with an external thread  6 . A crown  1  forms the second part of armature  50 . The inner circumference  3  of crown  1  is provided with an inner threaded portion  5  suitable for screwing onto external thread  6  of tube  7 . 
     Following head  9 , in the direction of the middle part of the timepiece, push button  51  has a stem  8 , which ends in a retaining means limiting the axial travel of the stem in armature  50 . In the example illustrated, the retaining means is formed by a screw  53 , screwed into the end face of stem  8  in the axial extension of the stem so that the head of screw  53  is stopped against the end face of tube  7  disposed on the side of the middle part of the timepiece. The screw thus enables the push button to be assembled on armature  50 . 
     A first push button return spring  10  is wound around push button stem  8 . This spring  10  is disposed between the bottom face  11  of push button head  9  and first retaining means  54  partially derived from armature  50 . In this first embodiment, first retaining means  54  comprises a second shoulder  2  arranged in crown  1 . Second shoulder  2  has a top face  57 , on which first spring  10  abuts, and a bottom face  58 , on which there abuts the top portion  59  of a cylindrical spacer  12  secured to stem  8 . The top end portion of cylindrical spacer  12  has a collar  12   a  whose function will be described below. The push button stem is moveable relative to spacer  12 . 
     After said first spring  10 , a second spring  13  is wound around stem  8 . One end of this second spring  13  is supported on said first retaining means  54  and the other end on a second retaining means  55 , partially derived from armature  50 . 
     This second spring  13  is arranged to bend and act as a valve spring if the pressure prevailing inside the timepiece is greater than the pressure prevailing outside said timepiece. Here, the second retaining means  55  comprises a third shoulder  18  arranged at the inner end of tube  7 . This third shoulder has a top face  60  on which a first O-ring joint  15  is mounted, followed by a sealing washer or ring  14 , and second spring  13  is disposed between said ring  14  and the bottom portion  61  of said spacer  12 . 
     It will be noted that, in practice and in a non-limiting manner, the stiffness of first spring  10  is greater than that of second spring  13 . 
     In this first embodiment and according to a first preferred variant, it is seen that cylindrical spacer  12  is made of deformable material so as to seal the push button. Preferably, cylindrical spacer  12  is made in a material having a shore hardness of between 50 and 100 and more preferably between 75 and 90. By way of non-limiting example, this spacer could typically be made of nitrile rubber (acrylonitrile-butadiene rubber NBR). 
     More particularly,  FIG. 1  shows the push button valve whose crown  1  is screwed onto tube  7 , with push button  5  in the rest position. In this situation the valve is closed, and second spring  13  is compressed between spacer  12  and ring  14 . 
       FIG. 2  illustrates the same screwed-in situation, where push button  51  is activated, with screw  53  of stem P activating a correction system of the timepiece, for example, to correct the date displayed on the dial. 
       FIGS. 1 and 2  show that the push button is sealed, on the one hand by deformable spacer  12 , whose collar  12   a  is clamped between the bottom face  58  of shoulder  2  and the end of the protruding portion  56  of tube  7  and on the other hand, at the tube-case connection by O-ring joint  83 . 
       FIG. 3  shows the push button-valve whose crown  1  is unscrewed from tube  7 . In this situation, second spring  13  is relaxed and the joint formed by collar  12   a  of the spacer is no longer active. Thus, joint  15  is capable of rising up against the return force of second spring  13  when the pressure inside the watch case is higher than that prevailing outside, which allows the valve to function. The compressed helium in the timepiece can escape through the space between cylindrical spacer  12  and the push button stem, or respectively the inner wall of tube  7 , then through the threaded portion  5  of crown  1 . 
     As seen in  FIG. 3 , it is to be noted that water resistance is entirely guaranteed by joint  15  and that the valve is thus also arranged to be unscrewed underwater. 
     Thus, when the crown is screwed onto the threaded portion of tube  7  as shown in  FIGS. 1 and 2 , the valve is inoperative and completely watertight. When the timepiece is employed in a liquid medium and at very great depths, the diver screws in crown  1 , which makes the push button valve completely watertight not simply by crushing collar  12   a  against the end of protruding portion  56  of tube  7 , but also by the additional effect of joint  15 , since second spring  13  develops an additional force on joint  15  when the crown is screwed in. 
       FIG. 4  shows a second variant of the first embodiment in which a second O-ring joint  16  has been added to a non-deformable spacer  12 , arranged between bottom face  58  of second shoulder  2  and a recess  62  made in spacer  12 . It is seen that second O-ring joint  16  abuts on end  63  of tube  7  when the crown is screwed onto the tube. In this variant, O-ring joint  16  plays the part of collar  12   a  illustrated in  FIGS. 1 to 3 . 
     It will be noted in the second embodiment shown in  FIGS. 5 and 6  that the push button includes a cylindrical armature  50  inside which there is a longitudinally-arranged through push button  51  formed of a head  9 , which has a bottom face  11  abutting against a first shoulder  52  made in armature  50  when manual pressure is exerted on head  9 . In this embodiment, armature  50  includes a single tube  7 . A first portion  90  of the bottom part  80  of the tube is screwed into the middle part of the timepiece and a second median portion  91  is provided with an O-ring joint  83  sealing the tube relative to said middle part. After head  9 , push button  51  includes a stem  8 , which ends in a screw  53  with a head for assembling the push button and limiting the axial travel of the stem in armature  50 . The head of screw  53  abuts against the end face of tube  7  disposed on the middle part side of the timepiece. 
     A first return spring  10  is wound around stem  8 . This spring is disposed between the bottom face  11  of head  9  and a first retaining means  54  partially derived from armature  50 . This retaining means includes a second shoulder  70  arranged in the inner wall of tube  7  and on which a washer  71  rests; the top face  72  of this washer acts as a support for first spring  10 . 
     After said first spring  10 , there is a second spring  13  wound around stem  8 , one end of which rests on said first retaining means  54  and the other end of which rests on a second retaining means  55  partially derived from armature  50 . The second spring is arranged to bend and act as a valve if the pressure prevailing inside the timepiece is higher than the pressure prevailing outside said timepiece. Here, the second retaining means  55  is the same as that cited in relation to the first embodiment, namely a third shoulder  18  arranged at the inner end of tube  7 . The third shoulder has a top face  60  on which a first O-ring joint  15  is mounted, followed by a ring  14 ; and the second spring  13  is disposed between said ring  14  and the bottom portion of said washer  71 . 
     More particularly,  FIGS. 5 and 6  show a push button-valve, whose push button is in the rest state in  FIG. 5  and in the activated state in  FIG. 6 . In both cases, the valve is potentially active whatever the position of the push button and operates in the same manner as described with reference to the push button-valve illustrated in  FIGS. 1 to 4 . Thus, when the pressure inside the watch case is higher than the external pressure, O-ring joint  15  can rise up against the return force of second spring  13 , which allows the pressurised air in the timepiece to escape through the space between the push button stem and the inner wall of tube  7 .  FIGS. 5 and 6  thus show an automatic valve, whereas  FIGS. 1 to 4  show a manual valve.