Time Setting Mechanism

This invention relates to wristwatches having time indicating hands, and more particularly to a time setting mechanism for such wristwatches.

There are known in the art a variety of change-over levers that are used to correct time indicating hands of wristwatches, one example of which is shown in FIG. 1. In a correction mechanism of the type employing change-over lever 10 and a gear wheel 18 for transmitting the rotation of a winding stem 14 often experience back-lash. When the winding stem 14 is pulled out and/or depressed under such a condition a minutes wheel 16 is unintentionally caused to rotate because a shift gear wheel 12 shifted by the pivoting of the change-over lever 10 does so while undergoing rotation. This is particularly true when depressing the winding stem 14 and is a major defect in the prior art since it causes the hands of the wristwatch to shift and thus indicate the incorrect time.

It is therefore an object of the present invention to provide a time setting mechanism for a wristwatch in which time indicating hands do not experience the above mentioned shift during operation of a time setting stem.

It is another object of the present invention to provide a time setting mechanism which makes it possible to remarkably reduce the thickness of a wristwatch.

These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partial plan view of a prior art time setting mechanism for a wristwatch;

FIGS. 2A and 2B are partial plan views of a preferred embodiment of a time setting mechanism for a wristwatch according to the present invention;

FIG. 3 is a cross sectional view of the time setting mechanism shown in FIGS. 2A and 2B;

FIG. 4 is another cross sectional view of the time setting mechanism shown in FIGS. 2A and 2B;

FIG. 5 is a cross sectional view of another preferred embodiment of the time setting mechanism according to the present invention;

FIGS. 6 and 7 are cross sectional views of another preferred embodiment of a time setting mechanism according to the present invention;

FIGS. 8 and 9 are cross sectional views illustrating another preferred embodiment of a time setting mechanism according to the present invention; and

FIG. 10 is a cross sectional view of a modified form of the time setting mechanism shown in FIGS. 8 and 9.

FIGS. 2A and 2B, 3 and 4 show a preferred embodiment of a time setting mechanism for a wristwatch according to the present invention. In this preferred embodiment, the time setting mechanism, which is generally indicated at 20, comprises a control stem or time setting stem 22 which radially extends relative to the movement 30 of the wristwatch. The control stem 22 carries at its end a pinion gear 22b serving as a setting gear. The pinion gear 22b is in mesh with a toothed portion 27a of a setting gear wheel 27. The control stem 22 is radially movable to an operative or time setting position and an inoperative or non-time setting position. This control stem has axially spaced large diameter portions 22c and 22d slightly larger than the pinion gear 22b and loosely fitted into a radially extending bore 21a of a base plate 21. The control stem 22 also has a small diameter portion 22a formed between the large diameter portions 22c and 22d. A setting lever 23 is pivotable about a pivot shaft 21b upstanding from the base plate 21 as shown in FIGS. 2 and 4 and forms a part of a change-over means as will be described later. The setting lever 23 has a neck portion 23a formed at its lower surface with a recess 23b with which the small diameter portion 22a of the control stem 22 engages. The setting lever 23 also has at its one end a setting lever pin 23d, a downwardly extending boss portion 23e, and a reset lever 23c freely mounted on the pivot shaft 21b and positioned by the setting lever pin 23d. The reset lever 23c is actuated together with the setting lever 23 and is adapted to make contact with a reset terminal 21f of an electronic circuit of the wristwatch at an operative position indicated at 23'c as shown in FIG. 2B, the reset terminal 21f being so located and mounted on the base plate 21 through an insulating bushing 21e. A setting lever spring 24 is mounted on base plate 21 and includes a first setting lever spring portion 24a for biasing the setting lever 23 toward the plate 21, and a second spring portion 24b for positioning or holding the setting lever 23 at one of a plurality of operating positions by recesses (two in the illustrated embodiment) that engage with the setting lever pin 23d. The setting lever spring 24 itself is positioned by a pin 21c and rivet 21d and is secured to the base plate 21 by a screw 34. A change-over lever 25 forms another part of the change-over means and has a recess 25a for engaging with the boss 23e of setting lever 23 and is pivotally attached to the bottom side of base plate 21 by the rivet 21d. A shift gear wheel 26 is mounted on the change-over lever 25. The setting gear wheel 27, which is rotatably mounted on base plate 21 by a rivet 21h, meshes with a first transmission gear wheel 28 mounted on the base plate 21 by a shaft 21g and rotatable on a first axis A1 as shown in FIG. 4. A second transmission gear wheel 29 is also rotatably mounted on the shaft 21 g fixedly supported by base plate 21 but on the bottom side of the base plate 21. The second transmission gear wheel 29 meshes with a minutes wheel 40 of a gear wheel train 35 of the wristwatch. The minutes wheel 40 cooperates with a minute wheel spring 43 to retain the transmission gear wheel 29 and prevent it from falling off. The minutes wheel 40 meshes with an hours wheel 41 and a center wheel and pinion 42, and a slip mechanism is provided between the center wheel pinion 42a and cannon pinion 42b of the center wheel and pinion 42.

Referring now to FIGS. 2A and 2B, FIG. 2A shows the state in which the control stem 22 is in the depressed or non-time setting position while FIG. 2B shows the state in which the control stem 22 is in the depressed or non-time setting position. First, with the wristwatch in its normally operating state and the control stem 22 depressed, a drive power is transmitted from an electro-mechanical transducer (not shown) to the minutes wheel 40 and hence to the second transmission gear wheel 29, whereas rotation of the control stem 22 under these conditions can be transmitted only as far as the setting gear wheel 27 and the first transmission gear wheel 28 so that the two rotation transmission paths are isolated from one another. If the control stem 22 is now pulled out, i.e., to a time setting position, the setting lever 23 will pivot to the new position 23' until the setting lever pin 23d is repositioned at 23'd by the spring portion 24b of setting lever spring 24. The control stem 22 is therefore positioned at 22' and the change-over lever 25 at 25' so that the shift gear wheel 26 is shifted to an engaging position 26' relative to the first axis A1 by the action of the change-over means 23 constituted by the setting lever and thus made to mesh with the first transmission gear wheel 28. The reset lever 23c mounted on setting lever 23 is shifted to position 23'c and makes contact with the reset terminal 21f to reset the associated electronic circuitry. Although not shown in FIGS. 2A to 4 a brake lever to be actuated by the change-over lever 25 is provided to provide a braking effect. If the control stem 22 in the position 22' is now rotated under these conditions the turning effort or torque can be transmitted from minutes wheel 40 to hours wheel 41 and to the center wheel and pinion 42 because the shift gear wheel 26 in the position 26' meshes with the first and second transmission gear wheels 28 and 29. Meanwhile the angle through which the center wheel 42b rotates is restricted by the brake lever described above with the torque resulting from rotation of the control stem 22 in position 22' causing slipping between the center wheel pinion 42a and cannon pinion 42b thereby allowing the hands 45, 46 of the wristwatch to be set. If the control stem 22 is now depressed to return it from position 22' to its original position, setting lever 23 returns to its original position from 23', change-over lever 25 to its original position from 25', and shift gear wheel 26 to its original position from 26'. Since change-over lever 25 actuates the brake lever only when in the position 25', returning the change-over lever 25 to its original position releases the brake. The reset lever 23c is similarly returned to its original position by the setting lever 23 and is therefor removed from the reset terminal 21f to restore the wristwatch circuitry to its normal operation.

In accordance with the embodiment mentioned above, the operation of the shift gear wheel 26 mounted on the change-over lever 25 is such that disengaging the shift gear wheel 26 from the first transmission gear wheel 28 leaves this gear wheel free of any externally applied torque since it is no longer meshing with a member capable of applying such a torque. The hands 45 and 46 of the wristwatch are therefore not shifted when depressing the control stem 22 at the end of a time correction.

FIG. 5 is a cross-sectional view of another preferred embodiment of the present invention, with like or corresponding component parts bearing the same reference numerals as those used in FIGS. 2A through 4 and operating in an identical manner. In this embodiment a first shift gear wheel 51 and second shift gear wheel 52 are supported by setting lever 23 and rotatable on the same axis A3. The setting lever 23 is thus capable of serving as a change-over means. More specifically, when the control stem 22 is in the depressed position the first and second transmission gear wheels 28 and 29 are drivably isolated from one another as in the first embodiment. Next, pulling out the control stem 22 moves the setting lever 23 to the position 23' so that the first shift gear wheel 51 moves to the position 51' and meshes with the first transmission gear wheel 28 while the second shift gear wheel 52 moves to the position 52' and meshes with the second transmission gear wheel 29. Under these circumstances the reset lever and brake lever operate in the same manner as the first embodiment. If the control stem 22 is now rotated the first and second transmission gear wheels 28 and 29 are drivably connected to one another by the first and second shift gear wheels 51 and 52 which rotate in unison as a single gear in the positions 51' and 52'. The hands of the wristwatch are therefore corrected in the same manner as the first embodiment.

FIGS. 6 and 7 show another preferred embodiment of a time setting mechanism according to the present invention, with like or corresponding component parts bearing the same reference numerals as those used in FIGS. 2-4. In this preferred embodiment, the second transmission gear wheel 29 is replaced with a minutes wheel 40, which is rotatably supported by the pivot shaft 21g supported by the base plate 21. The minutes wheel 40 is freely rotatably independently of the transmission gear wheel 28 and no drive connection is provided between the transmission gear wheel 28 and the minutes wheel 40 in the non-time setting state of the time setting mechanism. A shift gear wheel 126 is rotatably supported by the change-over lever 25 and comprises a first gear 126a and a second gear 126b rotatable on the same axis as the first gear 126a. As shown in FIG. 7, the shift gear wheel 126 is normally held in its inoperative position, i.e., when the control stem 22 remains in its depressed condition. Under these circumstances, the drive power is not transmitted to the minutes wheel 40 from the control stem 22 even when the control stem 22 is rotated, because the first and second gears 126a and 126b of the shift gear wheel 126 are out of engagement with the transmission gear wheel 28 and the minutes wheel 40, respectively. When the control stem 22 is pulled out to the time setting position, the change-over lever 25 of the change-over means is rotated about the pivot shaft 21d by means of boss portion 23e of the setting lever 23, and the shift gear wheel 126 is moved to its operative position. Under this condition, the first gear 126a meshes with the transmission wheel 28 and the second gear 126b meshes with the minutes wheel 40. Under these circumstances, if the control stem 22 is rotated, the pinion gear 22b of the control stem 22 rotates the setting gear wheel 27, which in turn rotates the transmission gear wheel 28. Since, in this condition, the transmission gear wheel 28 is held in engagement with the first gear 126a of the shift gear wheel 126 and at the same time the second gear 126b is in mesh with the minutes wheel 40, the rotation of the transmission gear wheel 28 is transmitted to the minutes wheel 40 by which the hands of the wristwatch is corrected. Other parts of the time setting mechanism of FIGS. 6 and 7 are identical to those of FIGS. 2A-4 and, accordingly, a detailed description of the same is herein omitted.

FIGS. 8 and 9 illustrate another preferred embodiment of the time setting mechanism according to the present invention, with like parts bearing the same reference numerals as those used in FIGS. 2A-4. In this illustrated embodiment, the second transmission gear wheel 29 is rotatably supported by the pivot shaft 21h by which the setting gear wheel 27 is also rotatably supported. The transmission gear wheel 29 is rotatable independently of the setting gear wheel (see FIGS. 9) and is in mesh with the minutes wheel 40 (see FIG. 8). A shift gear wheel 226 is rotatably supported by a pivot shaft 26c secured to the changeover lever 25. The shift gear wheel 226 comprises a first gear 226a engageable with the setting wheel 27, and a second gear 226b engageable with the transmission gear wheel 29. With this arrangement, when the control stem 22 remains in its inoperative position, i.e., depressed position, the changeover lever 25 maintains the shift gear wheel 226 in its inoperative position shown in FIG. 9. Under this condition, if the control stem 22 is rotated, the setting gear wheel 27 rotates about the pivot shaft 21h. Since, in this condition, the setting gear wheel 27 is not drivably connected to the transmission gear wheel 29, no rotation is transmitted to the minutes wheel 40. When, in contrast, the control stem 22 is pulled out, the setting lever 23 is moved so that the boss portion 23e of the setting lever 23 will move the change-over lever 25 to its operative position. In this case, the first gear 226a of the shift gear wheel 226 is brought into engagement with the setting gear wheel 27 and at the same time the second gear 226b of the shift gear wheel 226 is brought into engagement with the transmission gear wheel 29. Thus, the setting gear wheel 27 is drivably connected to the transmission gear wheel 29. Accordingly, if the control stem 22 is rotated under these conditions, the setting wheel 27 will rotate the transmission gear wheel 29 by means of the shift gear wheel 226. Since, the transmission gear wheel 29 is in mesh with the minutes wheel 40, the rotation of the control stem 22 will allow the correction of the time indicating hands.

FIG. 10 shows a modification of the time setting mechanism shown in FIGS. 8 and 9. The modification of FIG. 10 is identical in structure to the embodiment of FIGS. 8 and 9 except that the shift gear wheel 226' comprises a first gear 226'a rotatable on the pivot shaft 26c and a second gear 226'b rotatably supported by another pivot shaft 26'c carried by the changeover lever 25. The second gear 226'b is in mesh with the first gear 226'a and engageable with the transmission gear wheel 29 when the changeover lever 25 is moved to its operative position by the action of the setting lever (not shown). On the other hand, the first gear 226'a is engageable with the setting gear wheel 27 when the second gear 226'b engages with the transmission gear wheel 29. The time setting mechanism thus arranged will operate in the same manner as that of FIGS. 8 and 9, and, therefore, detained description of the same is herein omitted.

While it is obvious that the time indicating hands of the wristwatch in the embodiments discussed above are not shifted or disturbed when the control stem remains in its depressed condition, another advantage of the present invention is that the setting gear wheel is attached to the base plate by means of the rivet and therefore the undesirable movement of the setting gear wheel is prevented. In the prior art the setting gear wheel is rotatably mounted on the change-over lever and is therefore not disposed in a stable manner. This tends to allow the pinion gear of the control stem to disengage from the setting gear wheel. The structure of the present invention, however, precludes such disengagement and is particularly effective when applied to an extremely slender wristwatch construction where there is only a small meshing interface between the pinion gear of the control stem and the setting gear wheel. It is also obvious that the present invention can be applied to mechanical as well as electronic wristwatches.