Abstract:
The invention is related to a watch case equipped with a decoration piece ( 50 ) which has the particularity of being difficult to machine and having moreover dimensions of rather wide tolerances, namely plus or minus about a tenth of a millimeter around a reference dimension, whereas the manufacturers of the watch cases are able to ascertain usually a precision in the order of a hundredth of a millimeter. This handicap is overcome in providing a clearance between the decoration piece and the adjacent elements ( 20, 30 ), namely the middle of the watch and the bottom, and thanks to means ( 60, 70 ) ascertaining the maintenance of these clearances, these means exerting at the same time the functions of tightness and of shock dampening where the shocks occur on the clockwork-movement ( 10 ) or on the decoration piece ( 50 ), or on both.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a watch case, equipped at its circumference with a decoration piece that extends around a middle part of the case to which are connected a back cover and a glass plate, an inner surface of the middle part surrounding a clockwork movement supported by a circular piece and connected to a crown through an arbor. 
     2. Description of the Prior Art 
     The problem associated with the manufacture of watches of this type where the decoration piece is present for esthetic reasons only, is based on the incompatibility of the manufacturing precision figures when the decoration piece is made from a very hard and only low resilient material such as glass, crystal glass or precious or semi-precious stones; this problem is well known to watchmakers. In fact, whereas the cases are manufactured with a precision in the order of 0.01 mm, this precision cannot be respected with the above-mentioned hard materials where internal tensions are present which may lead to fissures and fractures of the machined material. The manufacturers cannot generally offer a better precision than about 0.1 mm, considerable deviations of the dimensions of different pieces which are successively manufactures being further unavoidable. 
     It is therefore highly desired to compensate the allowances described above. 
     Efforts have already been made to solve the problem. Thus, Swiss patent specification No. CH-A-654,167 discloses a watch case comprising an annular piece 7 made from a material whose machining is very difficult. However, the proposed means do really not bring about a solution of the above-depicted problem since certain portions of said piece must still be machined in order to respect precise dimensions (page 4, left column, lines 19 ff.). Now, it is just this type of machining which should be made superfluous by the present invention. 
     European patent No. EP-B1-0,150,746 also describes a watch case comprising a middle portion formed by two concentric rings, namely an inner ring which constitutes the very middle portion of the watch case, surrounding the clock movement, and an outer ring (or annular piece or decoration piece) exerting before all a decorating function. However, this piece, maintained between a bottom and a frontal plate (covering the inner ring on which it is cemented), must have essentially the same thickness as the inner ring. In fact, it is stated that, should the decoration piece be separated from the middle of the case by a seal, it is axially retained by the clamping force between the bottom and the frontal plate only, no other fastening means being provided. This solution is therefore not satisfactory since the thickness of the decoration piece must necessarily be machined in respecting, here again, precise dimensions. If, on one hand, the thickness of the outer decoration ring is higher than the required dimension value, the bottom cannot be correctly fastened against the middle portion (the inner ring), which will lead in a mostly undesired manner to a very rapid breakdown of the watch since neither the tightness nor the dampening of shocks are assured any longer; moreover, the decoration piece will be damaged during the mounting of said bottom on the middle portion. If, on the other hand, the thickness of that outer ring is lower than the required dimension value, it will begin to move in axial direction, and this movement will damage the ring with time, together with the undesired unaesthetic effect caused by a not wanted liberty movement. 
     Furthermore, the problems caused by the differences between the dilatation coefficients of the metal forming the middle portion of the case and the material from which the decoration piece is made, are even not dealt with and still less resolved. 
     SUMMARY OF THE INVENTION 
     The purpose of this invention is to overcome the above-discussed disadvantages. This purpose is fulfilled by a watch case of the above-indicated kind wherein clearances are provided between the decoration piece and the middle of the case and the bottom, respectively, in such a manner that said decoration piece is out of contact with the middle and with the bottom, and wherein means are provided and established in order to maintain said clearances. 
     Further features, advantages and special realizations of the invention will become evident from the following description and from the dependent claims whose contents are incorporated by reference into this specification. 
     The implementation of the means according to the invention is particularly advantageous not only because the drawbacks associated with the watch cases of the prior art are overcome, but also because the proposed present solution is remarkably simple, elegant and cheap. Moreover, the same means fulfill simultaneously and in an ideal fashion the functions of tightness and shock absorption. These means allow to realize the ideal synthesis always searched for, namely manufacturing costs reduced to a minimum, functioning reliability in all situations, selected esthetics and possible or polyvalent presentation variations. 
     A special embodiment of the invention will now be described in detail as a non-limiting example thereof, and reference is made to the attached drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawing, 
     FIG. 1 shows a half sectional view in the plane of 9.00 to 3.00 o&#39;clock, and 
     FIG. 2 is a partial top view at another scale. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The wrist watch can be seen in FIG. 1; the watch comprises a clockwork-movement  10  with a central axis  10 A, supported on a circular plate  11 , of a type known per se. It may be a mechanical movement, a quartz movement, etc., with a display by hands or with a digital display. The shown movement comprises hands  14 H (for hours) and  14 M (for minutes), driven on the hour-wheel arbor and the cannon-pinion arbor, respectively, generally indicated by  14 , as well as a dial face  18 . All these elements are stowed in a case composed of a middle portion  20 , a bottom  30  and a glass cover  40  which is connected to the middle portion  20  by means  41 . The middle  20  surrounds by its inner face  22  the set composed of the movement  10  and the circular plate  11  and comprises a nose or notch  27  which retains said dial face. The bottom is fastened under the middle, preferably in a removable manner, by means of fastening elements, for example by four screws  19  distributed at 1:30, 4:30, 7:30 and 10:30 o&#39;clock. A hand-setting rod  15 , traversing the middle  20 , is also (partially) shown with its crown  16  (in fine dash-dot lines) and a seal  17 . Until now, the shown elements are conventional ones and follow a usual and known construction, it being understood that the case itself may take different shapes (circular, oval, rectangular as shown in FIG. 2, etc.). 
     The middle  20  comprises an outer lateral face  21  opposed to the inner face  22 , these two faces extending in parallel to the axis  10 A of the watch case, and further comprises a lower plane surface  25  orthogonal to the axis  10 A and facing the bottom  30 . At the opposite, namely in the upper part, the middle comprises a shoulder  24 . A surface  23  of this shoulder which is preferably parallel to the face  25 , is oriented against the latter. The upper, visible surface of this shoulder is referenced as  28 . As to its composition, the middle may be made of different materials, especially of a metal such as steel, yellow or white gold, a combination of these two gold types, etc. The surface  28  may be provided with decoration or jewelry elements. It may comprise, for example, mounted precious or semi-precious stones. 
     The bottom  30  is composed of a preferably plane metallic plate that is delimited by its inner face  32 , its outer face  33 , and its lateral faces  31 . It comprises (see FIG. 2) sides 6:00 and 12:00 o&#39;clock, and connecting means  34  for fastening a wristband, as it is known to the one skilled in the art. 
     The case is completed by a decoration piece having essentially an esthetical function, or annular piece  50 . The shape of this annular piece should of course be understood in its largest sense, i.e. it is not limited to a circular shape. According to the present Example, this piece  50  is made from a hard and brittle material, thus difficult to be machined, such as glass. It surrounds the middle  20 —which determines its shape, seen from above (see FIG.  2 )—and is clamped between the middle and the bottom  30  under the conditions to be described below. As to its sectional shape, according to the representation of FIG. 1, it is defined by the inner face  51  (disposed opposite to the face  21  of the middle), lower face  52 , upper face  53  and laterally outer face  59 A. The faces  52 ,  53  are partially covered, respectively by the lower face  32  of the bottom and the lower face  23  of the shoulder  24  of the middle. The faces  52 ,  53  are preferably parallel to each other at the regions where they are covered as described. Clearances  56 ,  58 ,  57  which will be described later in detail extend between the faces  51  and  21 ;  53  and  23 ; and  52  and  32 , respectively. The piece  50  has a boring  55  in the axis of 9:00 to 3:00 o&#39;clock for allowing the passage of the hand-setting rod  15 . The diameter of this boring may be greatly superior to that of the rod. The boring opens into a groove or notch  59  having a usual and known shape, see FIG. 2, for permitting the operation of the crown  16  fixed to the outer end of the rod  15 . Since the piece  50  is a decoration piece, the structure, the relief and the finishing of the face  53  are particularly carefully done whereas the choice of the material and the quality are also determined by a sophisticated esthetic. 
     The piece  50  cooperates further with means  60 ,  70  permitting to maintain the clearances  56 ,  58 ,  57  and, consequently, to avoid that the decoration piece comes into contact with the neighboring elements, namely, the middle  20  and the bottom  30 . 
     These means fulfill at the same time the functions of tightness and of shock dampening. 
     According to a preferred realization, these means are dissociated, namely, composed of first and second means referenced as  60  and  70 , respectively. 
     The first means  60  are advantageously constituted by at least one compressible annular element, disposed within the angular region formed by the faces  21  and  23  of the middle  20  and the corresponding faces of the piece  50 . According to the Example, the means are composed by a toric sealing ring  60  partially seated within a groove  26 . The seal may exert, when the bottom  30  is mounted on the middle  20  by means of the screws  19 , a reaction force F 1  by seating upon a chamfer  54  that breaks the angle of the faces  51 ,  53 . The dimensions of the means  60  are defined such as to ascertain a clearance or gap  56  between the above described faces  21 ,  51  and a gap  58  between the faces  23 ,  53  in a reliable manner and especially during said mounting, said clearance not falling below a limiting value of, say, a tenth of a millimeter which allows to take care of the decoration piece under all conditions. 
     The second means  70  are constituted by an annular or a plane piece, according to the particular embodiment. Seen in the section shown in FIG. 1, this piece  70  is plane like the bottom  30  on which it is laid down. Its shape may be geometrically defined by its outer, inner and lateral exterior faces which are referenced by the numerals  72 ,  73  and  71 , respectively; in its annular embodiment, the piece  70  is necessarily additionally defined by its inner lateral face that is symbolically shown in FIG. 1 by the reference  74 . The means  70  are made of a soft and compressible material. If the piece  70  is a plane annular or a solid (full) one, it carries the reference  70 . 
     In FIG. 1, the means  70  correspond to the solid piece. They are disposed on the inner face  32  of the bottom  30 , the lateral exterior face  71  being on a level with the lateral face  31  of the bottom  30  or, see FIG. 1, slightly retracted therefrom. According to the annular embodiment (not shown), the piece  70  should extend under the lower face  25  of the crown, under the lower face  13  of the ring  12  of the circular piece  11 , and partially under the face  52  of the decoration piece  50 . This will say that the inner lateral face (symbolically shown by the reference  74 ) is on a level with the inner face (without reference numeral) of said ring  12  or, for a better safety, slightly exceeds the limit  74  in the direction of the axis  10 A of the clockwork-movement. 
     This minimal width of the crown of the annular piece (when this variant is selected) that extends between the faces  71  and  74  (or even slightly further from the latter) is important. 
     The reason thereof will now be explained. It is first reminded that, on one hand, the precision of the dimensions of the decoration piece after finishing is rather high compared with the usual manufacturing precision of especially the middle part. On the other hand, it is one aim of the invention to avoid damages such as the formation of fissures and fractures of the decoration piece, be it during manufacture and machining or be it during the mounting of the bottom to the middle, and to avoid tightness and shock absorption defects. All these damages or defects may be caused by pinch of said piece. Furthermore, it is intended to take advantage from the constraint based on the finishing imprecision of this piece  50 . 
     Thus, at a first place, such reference dimensions should be selected for the manufacture of the piece  50  that, disregarding the means  60 ,  70 , the theoretical clearance between the faces  21  and  51  be at least equal to a tenth of a millimeter, plus a predetermined value (D 1 +S 1 ), and that the thickness between the faces  52 ,  53 , measured in the regions where they are parallel and covered by the shoulder  24  and the bottom, corresponds to the distance between the planes  23 ,  25  of the middle minus a value in the order of a tenth of a millimeter, and minus a predetermined value (D 2 +S 2 ). 
     The values D 1 , D 2  are provided and calculated in order to absorb the effects following from the differences between the dilatation coefficient of the metal (middle  20  and bottom  30 ) and that of the mineral element (decoration piece  50 ), the first being sensibly greater than the second. This is another considerable advantage brought about by the providing of clearances between the decoration piece  50  and the neighboring elements that are preferentially made from a metal. The values Si, S 2  constitute safety margins. They may be in the order of a tenth of a millimeter or slightly lower. 
     Under these conditions, and taking into account the manufacturing allowances mentioned above and regarding especially the clearance  56 , when the final dimension at the end of machining the face  51  of the piece  50  is at its highest limit, a very slight clearance equivalent to (D 1 +S 1 ) will still separate this face from the face  21  of the middle. 
     The assembled watch case has the configuration that is shown in FIG.  1 . 
     Thanks to the means  60 , the clearances  56  and  58  are maintained in a reliable manner, these means exerting furthermore and simultaneously a sealing function and a shock dampening function in order to take care of the decoration piece  50 . 
     However, if the means  60  resolve a part of the problem set forth above, they may create a new one, namely a possible defect of the shock dampening function on the movement  10 . In fact, hypothetically, if the thickness of the piece  50  corresponds at its maximal allowance on one hand and, on the other hand, the piece  70  when it has an annular shape, extends only under the face  25  and partially under the face  52  and is compressed at this regions by the tightening action of the means fastening the bottom to the middle, the circular piece  11  may be not or only insufficiently held, and the clockwork-movement  10  may “swim” at every wrist movement and be subject to all shocks. Under the opposite hypothesis that the piece  50  has its minimal thickness allowance (and the piece  70  is the same), this defect does not occur; regarding the piece  50 , it will be sufficiently maintained thanks to the play of a sufficient compression of the means  70 . 
     In fact, the phenomenon of insufficient holding of the clockwork-movement has been observed with certain ones of the first prototypes which were all equipped with an annular piece  70  which extended only under the face  25  of the middle  20  and partially under the face  52  of the piece  50  (as defined above). 
     It was therefore necessary to resolve this new problem. This could be done in designing a piece  70  that extends also additionally at least under the circular piece  11 . Thanks to this feature, the clockwork-movement is safely blocked, namely the function of dampening shocks on the movement is well fulfilled. Simultaneously, the decoration piece  50  remains maintained in an ideal manner. In this way, the means  60 ,  70  cooperate for exerting simultaneously the triple function of clearance, of sealing and of dampening shocks against the clockwork-movement  10  and against the decoration piece  50 . 
     According to another embodiment (not shown), the means  60 ,  70  may be monolithic ones, i.e. that they are connected to each other through a tubular envelope made of semi-rigid synthetic material whose circumference, seen from above, corresponds to the circumference of the faces  21 ,  51 . In this case, the reference dimensions of the recess of the decoration piece  50  will be such that the latter may easily be slipped on said envelope. 
     Finally, it is to be observed that the present inventive conception comprises the provision of a clearance  16 E between the inner face  16 B of the crown  16  and the outer lateral face  59 B of the piece  50 . In an analogous manner, other clearances (not referenced) are provided on both sides of the crown  16 . The determination of this clearance  16 E and the other that are perpendicular thereto can be established in taking the clearances  56 ,  58  as a model. 
     It can easily be seen that the application field of the present invention is extremely wide, and that the invention may be out into action also in such cases where one is not bound by any constraint caused by machining.