Wristwatch with sacrificial pin

Abstract

Device for fastening a bracelet strand to a case of a watch. The device includes at least one fastening element allowing this bracelet strand to be detached from this case when this fastening element is subjected to a predetermined force or moment. Wristwatch including a case and at least one bracelet strand pivotally hinged about a shoulder of a pin forming such a device. This pin is a sacrificial pin which includes, on this shoulder, at least one area of mechanical resistance lower than the lowest mechanical resistance of this case and than the lowest mechanical resistance of this bracelet strand.

What is claimed is: 
     
         1 . A device for fastening a bracelet strand to a case of a watch, wherein the device includes at least one fastening element allowing said bracelet strand to be detached from said case when said fastening element is subjected to a predetermined force or moment. 
     
     
         2 . The device according to  claim 1 , wherein said fastening element includes at least one watchmaker's pin including at least one shoulder extending in an axial direction, in that said pin is a sacrificial pin and includes, on said shoulder, at least one area of mechanical resistance lower than 45 MPa. 
     
     
         3 . The device according to  claim 1 , wherein said fastening element includes at least one end link, and in that said end link is a flexible link including a first end to be secured to said case and a second end to be secured to said bracelet strand, and including means of absorbing torsion torque so that the reduction factor between a torsion torque applied to said second end and the resulting torsion torque at said first end is higher than a factor 10. 
     
     
         4 . The device according to  claim 2 , wherein said fastening element includes at least one end link, and in that said end link is a flexible link including a first end to be secured to said case and a second end to be secured to said bracelet strand, and including means of absorbing torsion torque so that the reduction factor between a torsion torque applied to said second end and the resulting torsion torque at said first end is higher than a factor 10, and wherein said end link includes, at said first end thereof, a said pin. 
     
     
         5 . A wristwatch including a case and at least one bracelet strand secured to each other, wherein the connection between said bracelet strand and said case includes a fastening element according to  claim 1 . 
     
     
         6 . The wristwatch according to  claim 5 , wherein said case and said bracelet strand are pivotally hinged about a shoulder of a pin which forms said fastening device and which is a sacrificial pin which includes, on said shoulder, at least one area of mechanical resistance lower than the lowest mechanical resistance of said case and than the lowest mechanical resistance of said bracelet strand. 
     
     
         7 . The wristwatch according to  claim 6 , wherein said case includes at least a first clevis mount with a first hole along a first axis, and in that said at least one bracelet strand includes at least a second clevis mount with a second hole along a second axis and is fastened to said at least one first clevis mount of said case by said sacrificial pin wherein said at least one shoulder is dimensioned to pass into said first hole and into said second hole to pivotally guide and secure said bracelet strand and said case, and in that the resistance of said pin to traction, shearing, torsion, and fatigue is lower than the lowest respective resistance of said case and of said at least one bracelet strand. 
     
     
         8 . The wristwatch according to  claim 7 , wherein each said first clevis mount includes at least a first lateral face which is radial relative to said first axis, in that each said second clevis mount includes at least a second lateral face which is radial relative to said second axis, and in that, when said at least one bracelet strand is in the assembled position hinged on said case via said pin, said first clevis mounts are alternated with said second clevis mounts defining interface areas in each of which a said first lateral face faces a said second lateral face, with an axial play comprised between 0.000 and 0.060 mm. 
     
     
         9 . The wristwatch according to  claim 8 , wherein at least one said area of low resistance of said pin is situated, when said at least one bracelet strand is in the assembled position hinged on said case via said pin, perpendicular to a said interface area. 
     
     
         10 . The wristwatch according to  claim 7 , wherein at least one said first clevis mount is bushed with a metal insert including said first hole thereof. 
     
     
         11 . The wristwatch according to  claim 7 , wherein at least one said second clevis mount is bushed with a metal insert including said first hole thereof. 
     
     
         12 . The wristwatch according to  claim 6 , wherein said peripheral shoulder of said pin includes, over the length thereof, first areas of higher resistance alternating with second areas of lower resistance. 
     
     
         13 . The wristwatch according to  claim 12 , wherein said first areas of higher resistance are made of rigid metal material or hard plastic material, and in that said second areas of lower resistance are made of flexible plastic material or elastomer overmoulded on first areas of higher resistance. 
     
     
         14 . The wristwatch according to  claim 12 , wherein at least one area of low resistance is formed by a said second area of lower resistance. 
     
     
         15 . The wristwatch according to  claim 12 , wherein at least one area of low resistance is formed by the interface area between a said second area of lower resistance and a said first area. 
     
     
         16 . The wristwatch according to  claim 7 , wherein said peripheral shoulder of said pin includes, over the length thereof, first areas of higher resistance alternating with second areas of lower resistance, and wherein each said first area of higher resistance faces a said first hole. 
     
     
         17 . The wristwatch according to  claim 7 , wherein said peripheral shoulder of said pin includes, over the length thereof, first areas of higher resistance alternating with second areas of lower resistance, and wherein each said first area of higher resistance faces a said second hole. 
     
     
         18 . The wristwatch according to  claim 6 , wherein said pin includes at least one notch in a said area of low resistance. 
     
     
         19 . The wristwatch according to  claim 6 , wherein said pin is made of a plastic material chosen from among polyoxymethylene (POM), polytetrafluorethylene (PTFE) filled with glass fibre, poly(p-phenylsulfide) (PPS) filled with glass fibre, polyamide-imide (PAI), polyether ether ketone (PEEK), or even polybenzimidazole (PBI).