Patent Publication Number: US-6655831-B1

Title: Case for an instrument of small volume including a manually removable back cover

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a case for an instrument of small volume, in particular a watch, including a middle part and a removable back cover applied under the middle part. 
     This type of case is commonly used to cover a wristwatch. The back cover may either be screwed on or snap fitted and may have a sealing gasket interposed between the back cover and the middle part. A back cover of this type can only be set in place or removed using special tools and these operations are generally reserved for a watchmaker, as is apparent in the two designs taken as an example hereinbelow. 
     Swiss Patent No. 251 447 shows a back cover snap fitted under a middle part. The case includes a middle part-bezel, a casing frame freely fitted in the middle part, a crystal the heel of which is clamped between the inner edge of the middle part-bezel and the casing frame, and a back cover. The back cover is fitted freely in the middle part and is pressed against a compressible sealing gasket lining the bottom face of the casing frame, by two levers each pivoting on an edge located on the inside each of the two opposite sides carrying the lugs of the middle part. 
     Swiss Patent No. 329 625 shows a back cover applied under a middle part by means of a screw system. This watch includes a crystal of which the edge bent towards the exterior is pressed against a gasket by a casing ring on which it rests. In order to hold the latter in the case, and so that it exerts a pressure against the edge, the back cover, whose contour is rectangular like the middle part, is fitted into the bottom opening of the latter and has, on its outer face, an annular housing, of which the outer wall is tangential to the sides of the opening and open at these tangent locations. In this housing there is arranged an externally threaded round ring, which is screwed into the middle part at the aforementioned tangent locations. Notches facilitate the screwing and unscrewing thereof. 
     In the design types briefly described above as in all the other designs known to date, if the watch is fitted with a battery in order to operate, the user will have no other choice than to give the watch to a person skilled in the art to change the battery once the battery reaches the end of its life. 
     It is true that in order to overcome this drawback, certain case back covers are fitted with a battery hatch which consists of a cap screwed on or fixed by a bayonet fitting in the back cover, the cap being provided with a screw slot which allows the user to open the hatch himself by means of a coin, as is implemented for example in the Swatch watch (registered trademark). 
     However, this solution would not be suitable for a battery, or other power source, with a large diameter as is found in pager watches or in watches fitted with a GPS system. It would also not be suitable for a particular watch including at least two batteries. For this type of instrument of small volume, it is thus necessary to find a solution which allows the entire back cover to be removed in order to have free access to the battery or batteries which have to be changed, such access having to remain simple to implement by the user, and without having to use any tools. 
     It will also be noted that in this type of instrument (pager or GPS for example) the power source has to be changed frequently, due to the high power consumption of the system. The battery change must thus be able to be effected quickly and by the user himself who will keep spare batteries on him. 
     SUMMARY OF THE INVENTION 
     In order to overcome this problem, the present invention proposes a back cover held under the middle part by means of at least one rail, this rail having a first longitudinal portion arranged to be slid into a groove made in the middle part and a second longitudinal portion arranged to cap an edge of the back cover when said first portion is introduced into said groove to fix said back cover under said middle part. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will appear from the following description, made with reference to the annexed drawings and giving, by way of explanatory but non limiting example, several advantageous embodiments of the invention, in such drawings: 
     FIG. 1 is a perspective bottom view of the case according to the invention, and in its most evolved meaning; 
     FIG. 2 is a cross-section of the case along the line II—II of FIG. 1; 
     FIG. 3 is a cross-section in the case along the line III—III of FIG. 1; 
     FIG. 4 is a blown up perspective view of the parts obturating the back of the middle part of the case according to the invention; 
     FIG. 5 shows a possible system for blocking the back cover of the case onto the middle part; 
     FIG. 6 is a partial cross-section of the case according to the invention in its simplest meaning; 
     FIG. 7 is a partial cross-section showing a construction variant to that shown in FIG. 2; 
     FIG. 8 is a perspective disassociated view of an alternative embodiment of the parts obturating the back of the middle part of the case according to the invention; 
     FIG. 9 is a simplified bottom view of the middle part; 
     FIG. 10 is a cross-section along the line X—X of FIG. 9; 
     FIG. 11 is a cross-section along the line XI—XI of FIG. 9; 
     FIG. 12 is a bottom view of the back cover of the case; 
     FIG. 13 is a cross-section along the line XIII—XIII of FIG. 12; 
     FIG. 14 is a top view of the plate for holding the back cover to the case; 
     FIG. 15 is a cross-section along the line XV—XV of FIG. 14, and 
     FIG. 16 is a cross-section in the assembly formed by the middle part of the watch and the parts obturating the back thereof. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The perspective view of FIG. 1 shows a watch case  1  according to the present invention and in its most evolved meaning. It shows a middle part  2  in which are integrated various horns  30  which will be used to secure the strands of a bracelet. Inside this middle part  2  are placed the watch movement and all the components which can accompany it, like for example, a pager or GPS electronic arrangement and a power source in the form of one or two batteries. A removable back cover  3  is applied under middle part  2 . If necessary, a sealing gasket  4  (see FIGS. 2 and 3) is inserted between middle part  2  and back cover  3 . 
     As FIG. 1 shows, the case of the invention is characterised in that back cover  3  is held under middle part  2  by means of two rails  5  and  6  located on either side of back cover  3 . As is visible in FIG. 2, which is a cross-section along the line II—II of FIG. 1, rail  5  has a first longitudinal portion  7  arranged to be slid into a housing or groove  9  made in middle part  2 . Rail  5  also has a second longitudinal portion  11  arranged to cap an edge  13  of back cover  3  when said first portion  7  is introduced into said housing or groove  9 . FIG. 2 also shows rail  6  constructed in a similar way to rail  5 . Thus, rail  6  has a first longitudinal portion  8  arranged to be slid into a housing or groove  10  made in middle part  2 . Rail  6  also has a second longitudinal portion  11  arranged to cap an edge  14  of back cover  3  when said first portion  8  is introduced into said housing or groove  10 . It will thus be understood that when rails  5  and  6  are in place, back cover  3  is fixed under middle part  2 . 
     In order to complete case  1  shown in FIGS. 2 and 3, middle part  2  carries on its upper portion a bezel  31  under which a crystal  32  is applied. The sealing between bezel  31  and crystal  32  is assured by a sealing gasket  33 . The sealing between bezel  31  and middle part  2  is assured by a sealing gasket  34 . 
     The invention could stop there and merely arrange two rails  5  and  6  to block back cover  3  under middle part  2 . In this case, in order to remove back cover  3 , the user slides rails  5  and  6  one after the other out of their respective housings, after which back cover  3  can be taken off. In order to facilitate this removal, each of the rails may be provided with a protruding portion at its end (not shown in the drawings). In order to close the case, back cover  3  is applied under middle part  2  and first of all first portion  7  of rail  5  is made to slide into its groove  9 , second portion  11  of this rail then resting on edge  13  of back cover  3 , then first portion  8  of rail  6  is made to slide into its groove  10 , the second portion of this rail then resting on edge  14  of back cover  3 . In the case which has just been explained, it will be noted that the rails are independent of each other and not necessarily parallel to each other. 
     It was however deemed useful and convenient to join the two rails  5  and  6  by a crosspiece  15  as shown in FIGS. 1,  3 ,  4  and  5 . Crosspiece  15  forms with rails  5  and  6 , arranged in parallel, a stirrup referenced  16  which is seen clearly in FIGS. 1 and 4. This stirrup  16  has the advantage of having on the one hand a single fastening part which is more difficult to lose and on the other hand, gripping means  17  for removing rails  5  and  6  simultaneously and manually from their respective housings  9  and  10  to thereby separate back cover  3  from middle part  2 . An example of the gripping means will be described now. 
     Gripping means  17  are illustrated in FIGS. 1 and 3. Crosspiece  15  is provided with a bulge  18  and back cover  3  is provided with a hollow or slot  19  which faces bulge  18 . In order to remove stirrup  16 , one slides a fingernail into hollow  19  until the point of the fingernail rests on bulge  18 . A force (arrow A) is exerted by the fingernail against bulge  18 , which has the effect of releasing crosspiece  15  from middle part  2  (arrow B) and removing rails  5  and  6  from their housings. 
     FIG. 4 illustrates the operations to be effected to close the case. One starts by applying back cover  3  under middle part  2  in the direction of arrow C. A certain force is maintained on back cover  3  in order to squash sealing gasket  4  slightly while the end of rails  5  and  6  is being introduced into their housings and they are slid, in the direction of arrow D, to the bottom of their housings, by pressing on crosspiece  15 . 
     In order to act as a counterpart to bulge  18  and thus to assure a certain symmetry for back cover  3 , the back cover is fitted with a second bulge  35  (FIGS.  1  and  3 ). 
     Once in place and as described hereinbefore, stirrup  16  is not protected from inadvertent removal due, for example, to an object appearing in front of the gripping means with which crosspiece  15  is provided. In order to avoid this, back cover  3  may be fitted with a notch  20  as shown in FIG.  5 . This notch  20  is capable of accommodating a locking piece  21  arranged on crosspiece  15 . This locking piece has, with respect to crosspiece  15 , sufficient resilience to bend when it abuts, via its inclined plane  36 , edge  37  of back cover  3  until its tip falls into notch  20 . To release the locking piece, one need only act on plane  36  with a fingernail to make it bend and thereby release all of stirrup  16 . 
     The cross-section of FIG. 6 shows a watch case  1  according to the present invention and in its simplest meaning. Here, back cover  3  is held under middle part  2  by means of a single rail  5 , which has, let us not forget, a first longitudinal portion  7  arranged to be slid into a groove  9  made in middle part  2  and a second longitudinal portion  11  arranged to cap an edge  13  of back cover  3 . In this case, as appears in the right part of FIG. 6, the other edge  45  of back cover  3  ends in a point, arranged to be housed in a groove  9  arranged in middle part  2 . In order to apply back cover  3  under middle part  2 , one starts by introducing pointed edge  45  into groove  9  at a certain angle. Back cover  3  is then folded down under middle part  2  and back cover  3  is fixed by introducing rail  5 . 
     Whether in the simplest meaning of the invention (FIG. 6) or in its most evolved meaning (FIG.  2 ), rails  5 ,  6  have a Z-shaped cross-section, first longitudinal portion  7  including a first rectangular heel which slides into groove  9  and second longitudinal portion  11  including a second rectangular heel whose top face  40  rests on edge  13  of back cover  3  (see FIG.  6 ). 
     The invention is not limited to this cross-section which may take other profiles such as for example, that shown in FIG.  7 . Here, first longitudinal portion  7  of rail  5  includes a rectangular heel slid into groove  9  and second longitudinal portion  11  of rail  5  includes a corner having an inclined face  41  arranged to rest on an edge  13  of back cover  3 , this edge being tapered. 
     In the following description, the elements which are identical to those previously described with reference to FIGS. 1 to  7  will be designated by the same numerical references. For a detailed description of these elements, reference will be made to the corresponding passages of the preceding description. 
     The perspective view of FIG. 8 shows middle part  2  of watch case  1  which carries several horns  30  which serve to attach the strands of a bracelet. As for the variant illustrated in FIG. 4, the operations to be effected to close case  1  require first of all applying back cover  46  under middle part  2  in the direction of arrow E. A certain force is exerted on back cover  46  to squash a sealing gasket  48  and ensure that said back cover  46  is suitably applied under middle part  2 . The end of rails  5  and  6  is then introduced into their respective housings  9  and  10  and they are slid, in the direction of arrow F, to the bottom of said housings  9  and  10 . 
     According to the variant shown in FIG. 8, rails  5  and  6  are connected to each other by a holding plate  50  which, when rails  5  and  6  are slid into their housings  9  and  10 , caps back cover  46  of case  1 . More precisely, and as was described previously, rails  5  and  6  each have a longitudinal portion, respectively  7  and  8 , arranged to be able to be slid into the housings or grooves  9  and  10  made in middle part  2 . Thus, when rails  5  and  6  are in placed, back cover  46  is fixed under middle part  2 , pressed against the latter by holding plate  50 . 
     Holding plate  50  has multiple advantages. First of all it constitutes a single pieces which is less easy to lose. It also has gripping means  52  which will be described hereinafter to remove rails  5  and  6  from grooves  9  and  10 . As it covers almost the whole of the surface of back cover  46 , holding plate  50  protects the latter against scratches or other external attacks. Finally, with respect to stirrup  16  described hereinbefore, holding plate  50  gives the assembly which it forms with rails  5  and  6  an improved rigidity. 
     In order to remove back cover  46 , the user has to slide rails  5  and  6  out of their housings  9  and  10  made in middle part  2 , after which back cover  46  can be taken off. In order to facilitate this operation, middle part  2  (shown schematically in FIGS. 9 to  11 ) has on its opposing transverse edges  54  two symmetrical grooves  56  which are open towards the bottom of case  1 . When back cover  46  is fixed under middle part  2 , it covers by its facing edge  58  one of the two grooves  56 . The end of one of rails  5  and  6  need then only be slid into groove  56  covered by back cover  46  and to use this rail  5  or  6  like a lever arm to detach said back cover  46  from middle part  2 . Of course, this example is given purely by way of illustration, and middle part  2  may only include a single groove  56  open towards the bottom to allow back cover  46  to be removed. Advantageously, holding plate  50  is capable of having a bulge which, in the closed position, obturates facing groove  56 , which substantially improves the aesthetic appearance of the watch. 
     Gripping means  52  are shown in FIGS. 12 and 13 relative to back cover  46  of watch case  1  and in FIGS. 14 and 15 which concern holding plate  50  of said back cover  46 . Holding plate  50  has a tongue  60  on the top face of which is provided a bulge  62 . When the two rails  5  and  6  are slid to the bottom of housings  9  and  10 , bulge  62  is snap fitted into a groove  64  which faces said bulge  62  and which is provided on the outer surface of back cover  46 . 
     To remove holding plate  50 , the back cover has a hollow  66 . The user then slides a fingernail into hollow  66  until the tip of the fingernail slightly raises tongue  60  of holding plate  50  and releases bulge  62  from groove  64 . In the same movement, the user pushes back holding plate  50  which has the effect of removing rails  5  and  6  from their housings  9  and  10 . 
     In order to facilitate the passage of bulge  62  of tongue  60  when rails  5  and  6  penetrate housings  9  and  10 , back cover  46  includes a chamfer  68  which has an inclined face on which bulge  62  can slide. 
     The invention which has just been described shows that an instrument of small volume can be provided with a back cover which can be set in place or removed without the user using any tools. Thus, if a battery has to be changed frequently, the user does not need to request the assistance of a specialist.