the inventive wristwatch includes a middle 1 in which a watch movement is lodged . a winding button 10 is connected to a winding shaft ( not represented ) and makes it possible to set the watch movement &# 39 ; s time and / or regulate other functions . the strap 4 of the watch is constituted of a single end whose two extremities 40 and 41 are fastened to the watch case . the extremity 41 is thus fastened , for example by means of a spring pin or other means , to the upper side at 6 o &# 39 ; clock of the middle 1 . the other extremity 40 is fastened at 12 o &# 39 ; clock on a base 3 of clasp described further below . the strap is advantageously moulded or injected in a flexible and extensible material , for example in a material on the basis of silicone , in order to perfectly adapt to the wearer &# 39 ; s wrist . a profiling 45 is preferably provided on the inside side of the strap to improve the skin &# 39 ; s respiration and reduce sliding . the watch case further comprises a clasp extension 2 . one extremity of the extension is connected by a first hinge 20 ( fig4 ) to the lower side of the middle , at 12 o &# 39 ; clock , whilst the other extremity of the extension is articulated by means of a second hinge 21 with the clasp base 3 at 6 o &# 39 ; clock . following an advantageous embodiment , the pivoting articulation 20 is a hinge designed for being easily disassembled in order to easily isolate the middle from the other parts of the wristwatch . this is notably useful for performing different operations , notably for casing up the movement , the dial and the hands or for performing different tests , such as tightness tests , or even for making easier different repair interventions if necessary . to this effect , the hinge 20 includes a removable pin 22 , visible in fig4 . in the illustrated preferred embodiment , the extension is formed of a hollow metallic frame ( stirrup ), which notably allows the weight of the watch case to be reduced and the bottom of the middle 1 to be accommodated if this bottom is protruding . preferably , as is clearly visible in particular in fig2 , the extension 2 has the shape of an open stirrup whose base is articulated with the base 3 through the intermediary of the hinge 21 . thus , this particular shape of extension makes it easier to lodge the extremity 40 of the strap under the middle 1 . however , a clasp extension in the form of a full blade or formed itself of an elastic material can also be conceived within the frame of the invention . furthermore , it is also possible in the frame of the invention to use clasp extensions in several elements to further increase the clasp &# 39 ; s elongation when the clasp is opened or to improve the comfort of opening . clasps integrated to the case of the butterfly type can thus be used . the base 3 is designed to come and rest against the wrist when the watch is worn . the bloc middle 1 — base 3 preferably forms a unit of monolithic aspect when the clasp is closed . to this effect , the base 3 and the middle fit one against the other without threshold at their junction . the base 3 includes a recess 30 sufficiently large and deep for lodging there the entire extension 2 is folded position . the extension 2 is thus dissimulated between the base and the middle when the watch is worn . as can be seen in particular in fig3 , the recess 30 also allows the extremity 40 of the strap 4 to be lodged . the depth with which the end 40 is engaged in the recess 30 can be adjusted to regulate the useful length of the strap according to the size of the wrist . in the illustrated embodiment , the strap 4 is held in the base 3 by a two - position eccentric cam 34 that can pivot parallel to the axis 3 o &# 39 ; clock - 9 o &# 39 ; clock between a position where the strap is wedged between the cam 34 and the base 3 and an adjustment position ( not illustrated ) where the interstice between the cam 34 and the base 3 is sufficient to have the strap 4 slide . the strap is thus held by compression of an arbitrary portion of one of its upper or lower sides and / or by friction against the elements 3 and 34 . as previously mentioned , the strap is preferably of an elastic material , so that it takes up its form again when the pressure of the cam 34 is relaxed . the cam 34 can preferably be freed only when the clasp 1 , 2 , 3 is open ; when the watch is closed , the case 1 blocks the cam &# 39 ; s rotation , thus preventing an accidental maladjustment of the strap &# 39 ; s length . the cam 34 is preferably arranged in such a manner as not to be disengaged by pivoting without a certain resistance , even when the clasp is open , so as to allow the clasp to open without risk of accidentally misadjusting the strap &# 39 ; s length . the resistance to the pivoting of the cam 34 can be for example caused by an increased compression of the strap during rotation of the cam . in an embodiment not illustrated , the cam 34 can be released only by acting on an additional control organ , for example a push - button , or by lifting one of the portions of the strap . the cam 34 can also be constituted of several elements . the visible portion of the cam 34 preferably has the same shape and visual aspect as the extremity 400 of the strap connected to the other side of the case and thus engages between two horns 13 of the middle . following a preferred embodiment , at least one banking 35 works with the cam 34 to prevent the latter from rotating around its axis . preferably , the cam &# 39 ; s rotation angle will be limited to a value lower than 90 °. by way of example visible in fig6 and 7 , at least one banking 35 is borne by the cam 34 and protrudes from at least one of its extremities . as can be seen in fig6 , when the cam 34 is in open position , the banking 35 coming into contact with the portion 37 of the horn 37 of the base , blocks the cam &# 39 ; s rotation . in this position , the extremity 40 of the strap can freely slide under the cam . in the closed position of the cam 34 , represented in fig7 , the banking 35 comes into contact with the exterior edge 38 of the base 3 whilst the cam 34 immobilizes by compression the extremity 40 of the strap . it will be noted that the maximal opening of the rotation angle of the cam can be adjusted by using the banking &# 39 ; s dimensions . the length of the recess 30 is preferably maximal , i . e . it is equal to the length of the base 3 minus the thickness of the recess &# 39 ; s edge . the cam 34 is placed so as to rest as far as possible from the extremity of the recess closest to the articulation 21 . this particular arrangement allows the distance between the cam 34 and the bottom of the recess close to the hinge 21 to be increased and thus the range of adjustment of the strap &# 39 ; s length to be maximized . the strap 4 is engaged under the extension 2 in the base 3 ; it is thus far from the bottom of the middle 1 , which can be prominent according to the thickness of the used movement . thus , the bottom of the watch / movement will not disturb the engagement of the strap . furthermore , the cam is arranged to exert a considerable pressure on the entire width of the strap . in this manner , the risk of the bracelet sliding outside the recess when only a small length of strap is engaged in the clasp can be minimized . by distributing the holding force of the cam 34 on the entire width of the strap , one furthermore reduces the local pressure and thus the risk of durably marking the surface of the strap . the resting surface of the base 3 on the lower side of the strap is preferably lower than the contact surface between the cam 34 and the upper side of the bracelet . this particular arrangement allows the strap to be held firmly thanks to the considerable pressure on the lower side whilst minimizing the risk of marking the strap &# 39 ; s upper side . holding the strap by friction and / or compression allows the inventive watch case to be used with any type of flexible strap , including leather or textile straps in which it would be difficult to provide fastening grooves or ribs . banking means , for example bankings working on the case and on the strap or an ardillon engaged in a hole through the strap can however also be used . the extremity 40 of the strap 4 is connected to the base of the watch case . the traction of this extremity is thus exerted following a more or less straight comprised in the main plane of the base . thus , the swinging torque on the case is minimal and the latter &# 39 ; s lower side at 12 o &# 39 ; clock does not risk lifting even if the bracelet is worn highly tensed . the extremity 41 of the strap connected to the case is preferably bent with a step 400 so that the traction force of this extremity is also exerted along a straight close to the wrist and more or less contained in the main plane of the base 3 . the lower side of the strap 4 is thus the closest to the wrist &# 39 ; s skin on its entire length , which is more aesthetic , more comfortable and improves the watch &# 39 ; s hold even during sudden movements . the watch case 1 comprises a mechanical locking device allowing the clasp to be locked in folded position . said mechanical locking device can , as in the example represented in fig4 , comprise two push - buttons 11 and 12 capable of acting on elastically deformable elements . as can be seen in fig4 , the push - buttons 11 and 12 are placed on the two lateral sides of the middle 1 . it can be seen that the push - button 12 allows a mobile hook 120 connected to the middle 1 and working with a banking 33 on the base to be actuated ( fig5 ). the push - button 12 can be pressed against the action of a spring or a blade , not represented , to disengage the hook 120 from the banking and thus open the clasp . a similar but symmetrical disposition is found on the other side of the case . the clasp can preferably be only opened by pressing simultaneously on the two push - buttons 11 , 12 and then by lifting the middle 1 relatively to the base 3 . the mobile hook 120 advantageously comprises a beveled side 121 , visible in fig4 , allowing the clasp - case to be closed again and the hook 120 to be pushed in without having to press on the bush - button 12 . a symmetrical beveled side , not represented , is also found on the hook 11 . the arrangement of the push - buttons on the middle 1 rather than on the base 3 allows them to be moved away from the wrist and thus the risk of injury to the wearer to be reduced . the winding button 10 is accessible even when the clasp is folded , so that it is not necessary to open it to set the time . according to a preferred embodiment of the invention , the winding button 10 is placed at 9 o &# 39 ; clock so that it cannot in any way come into contact with the back of the user &# 39 ; s hand . a locking of the middle 1 on the extension 2 or of the base 3 on the extension , is also conceivable within the frame of the invention . the illustrated locking of thee base on the middle however has the advantage of holding the whole case 1 , 2 , 3 firmly in closed position . the base 3 comprises a semi - circular notch 32 placed opposite the winding button 10 in folded position . in the same manner , the push - buttons 11 and 12 preferably rest in notches 31 respectively 36 of the base . this particular arrangement allows the winding button and the push - buttons 11 and 12 to be placed close to the junction line between the base and the middle and thus to partially hide this line or at least to make it less visible . the watch case that is the object of the present invention will be particularly suited to persons doing certain sports , such as golf in particular .
watch case comprising an unfolding clasp for a flexible strap , said unfolding clasp comprising : a middle connected to a first end of the strap , a base connected to the second end of the strap , an extension , connected in articulated fashion to the middle and to the base , wherein the articulations between the middle and the extension and between the base and the extension are arranged in such a manner as to allow the middle , the extension and the base to superimpose in folded position , and to be juxtaposed in unfolded position , a regulating cam for holding by compression and / or friction the strap against the base , the cam being capable of being swung to increase or reduce in a reversible manner the length of in folded position of the strap .