Wristwatch case and wristlet assembly
BACKGROUND OF THE INVENTION 
     The invention relates to wristwatches. 
     A conventional method of securing a wristlet to a watch case is to provide the case with lugs or horns joined by a spring-loaded bar. U.S. Pat. No. 1,806,439 (Barton) discloses a C-band of spring metal having loops formed therein for cooperation with such bars. In this construction, the spring band simply replaces the classic strap or bracelet sections, and the horns remain visible. 
     Japanese Utility model No. 1,018,350 (Citizen Watch Co. Ltd.) proposes a single-piece wristlet of plastic material or rubber having a thick central part with a recess in which the watch case is embedded, the conventional securing horns and bars thus being dispensed with. However, using this system, each model of watch case must have a special wristlet. 
     An object of the invention is to provide a wristwatch in which a case is mounted on a wristlet in a manner to enable easy interchange, by providing the rear part of each watch case and a case-receiving part of the wristlet with a complementary shape. 
     Another object of the invention is to employ the conventional and well-tested horn and bar securing system while concealing the horns from view whereby the watchcase and bracelet may have a pleasing aesthetic appearance. 
     SUMMARY OF THE INVENTION 
     In a watchcase according to the invention, a rear face of the case includes a rearwardly facing generally flat peripheral first shoulder and a back protruding rearwardly from the peripheral first shoulder. The back has two pairs of wristlet-securing horns extending from opposite sides of the back and disposed within the bounds of the peripheral first shoulder, each pair of horns having outer faces and facing inner faces. The front face of a case-receiving central part of the wristlet has a complementary shape to the rear face of the bracelet. It includes: two spaced-apart second shoulders each of which bears against a part of said first shoulder of the case and each including a pair of lateral extremities shaped to fit about the outer faces of a pair of horns of the case; a middle portion inset from said second shoulders complementary to at least a part of the rear surface of said back of the case; and two bulges joining said second shoulders to said inset middle portion, each bulge extending from between the extremities of the respective second shoulder and being shaped to fit between a pair of horns of the case. The rear face of the central part of the wristlet has a recess under each of said bulges and lateral openings through said bulges facing said extremities of said second shoulders. A pair of wristlet securing bars, preferably of the spring-loaded type, are disposed in said recesses, end parts of these bars removably securing the horns of the case between said extremities. 
     The wristlet is preferably molded in a single piece of semi-rigid synthetic plastic material, said central case-receiving part being extended by two tapering resilient curved arms. 
     The front face of the case preferably includes an integral bezel, the case being molded in a single piece of synthetic plastic material. 
     Hence, the front face of the case-receiving central part of the wristlet may be molded with substantially the same shape as part of the mold for forming the rear face of the case. The cases are preferably molded as disclosed in my copending application Ser. No. 499,191, using a single first mold to define a common rear face for several series of cases, and several second molds for providing front faces of different shapes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will now be specifically described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is an axial cross-section and side elevation of a first form of wristlet; 
     FIG. 2 is a similar view of a modified form of wristlet, with a watch-case shown in a dot-dash line; 
     FIG. 3 is a top plan view of the wristlet of FIG. 1; 
     FIG. 4 is a cross-section taken along line IV--IV of FIG. 1; 
     FIG. 5 is top plan view of a further form of wristlet, with a watch case shown in a dot-dash line; 
     FIG. 6 is a cross-section taken along line VI--VI of FIG. 5; 
     FIG. 7 is a rear perspective view of a watch case with a fitted wristlet-securing bar; 
     FIG. 8 is a perspective view of the central part of another form of wristlet; and 
     FIG. 9 is an axial cross-section and side elevation of the case of FIG. 7 secured on the wristlet of FIG. 8. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The wristlet 1 shown in FIGS. 1, 3 and 4, molded from a single piece of resilient plastic material, comprises two like incurved arms 2 and 3 extending from a central case-receiving part 4, the bracelet being symmetrical about a central plane A. The arms 2, 3 have thick ends 2a, 3a adjacent part 4, and taper to narrow free ends. The material is sufficiently flexible to allow separation of the free ends of the arms for fitting the wristlet on a wrist, and removing it. 
     The central part 4 has a flat middle part or bottom 4a inset between flat shoulders 4g adjacent ends 2a, 3a. Shoulders 4g have lateral extremities 4f with inner faces at approximately 45° (FIG. 3) and are joined by central bulges 4b to the bottom 4a. The rear face of part 4 (FIG. 4) has recesses 4e under bulges 4b, and the bottom 4a is joined to arms 2, 3 by lateral bridges 4d. Openings 4c open through the bottom 4a and through the lateral faces of bulges 4b/recesses 4e facing the extremities 4f. 
     FIG. 2 shows a modified form of bracelet including holes 7 in the extremities (as 4f of FIG. 1) for receiving the ends of bars passing through horns 5 of a watch case 6. With the bracelet of FIG. 1, bars for securing the wristlet to a watch case fit in holes in the horns of the case, as will be described later. 
     FIGS. 5 and 6 show another form of wristlet formed of two discrete like arms 8, 9 which can be interconnected to form a flat bottom 11 to receive the back of a case 10. In addition to a shoulder and a bulge, as before, each arm 8, 9 has a section of a middle portion, including a projection 12, 13 with a stepped end 12a, 13a interfitting in a complementary step in the opposite arm, 9 or 8 respectively. The wristlet arms are held securely together, and to case 10, by placing bars 15 in recesses 16 in the underside of the wristlet, ends of these bars engaging in horns of case 10, as will be described later. 
     FIG. 7 shows a case 20 with a rear face delimited by a flat rearwardly-facing generally oval peripheral shoulder 21 and having a back 22 protruding centrally from shoulder 21. Back 22 includes two pairs of horns 23 each having a curved outer face 24. The pairs of horns 24 have facing flat inner faces 25 with holes 26 for receiving the ends of a spring-loaded wristlet-securing bar 27. Between each pair of horns 23 is a recess 28 inset below shoulder 21 and extending up to a flat central part of back 22. Lateral parts 22a of back 22, corresponding to the horns 23, are slightly inclined to the flat central part. 
     The case 20 also has a front face 29 including an integral bezel 30 supporting a glass 31. The case, including bezel 30, is molded in a single piece of plastic material, and houses a conventional movement and time display, not shown. 
     Case 20 is mounted on a wristlet 32 as shown in FIG. 9. Wristlet 32, molded from a single piece of plastic material, FIG. 8, has two like curved resilient arms 33, 34 tapering from a central case-receiving part 35 the front face of which is limited by flat spaced-apart shoulders 36, 37. These shoulders have lateral extremities 36a, 37a having curved inner faces 36b, 37b complementary to the outer faces 24 of horns 23. Inset between shoulders 36, 37 is a flat middle portion 38 of part 35 having slightly upwardly inclined edges 38a. The central parts of shoulders 36, 37 between the pairs of extremities 36a, 37a are joined to the middle portion 38 by bulges 39, 40 respectively, each bulge being shaped to fit exactly in a recess 28 of case 20. In the rear face of part 35, under bulges 39, 40 are recesses 41 having lateral openings 42 through the bulges facing the curved faces 36b or 37b of extremities 36, 37. These recesses 41 are accessible from the rear of the wristlet, for the insertion of bars 27 whose ends pass through openings 42 and engage in holes 26 to firmly hold the horns 23 of case 20 which are placed between the complementary extremities 36a, 37a. 
     When the case 20 is thus fitted, FIG. 9, a part of back 22 bears against portion 38 of the wristlet. The inclined lateral parts 22a of the back rest on edges 38a from which they protrude laterally. As shown in the right hand part of FIG. 9, the extremities 37a (and 36a) envelop part of the curved outer faces 24 of horns 23, and thus conceal the horns. Each bar 27 rests against the bottom of a recess 28. 
     Although the back 22 of case 20 is shown disposed centrally of the peripheral shoulder 21, it is possible to dispose this back eccentrically to provide a case with an assymetric front face 29. Also the shoulder 21 and hence the front face 29 of the case may be of various shapes, such as circular, as case 10 (FIG. 5). Also the long axis of an oval or generally rectangular case could be disposed parallel to bars 27, instead of perpendicular thereto as shown in FIG. 7. The peripheral shoulder 21 of the case may extend continuously around the entire periphery, or may also be in two parts as shown in FIG. 7. 
     When, as preferred, series of case 20 are molded all with an identical rear face of complementary shape to part 35, and with front faces 29 of different shape, as set out in my copending application Ser. No. 499,191, there is considerable scope for interchanging cases of different shapes on wristlets for example of different colors, whereby the wearer can readily adapt the wristwatch to match different ensembles or make-up. 
     The form of recesses (4e or 41), which taper along the length of the arms of the wristlet, facilitates insertion of the bars while allowing ready access from the rear of the wristlet for removal, for example by means of a knife blade.