Abstract:
An electronic wristwatch includes an electronic circuit such as a lead frame with extending conductive strips providing a first battery contact terminal and switch contact terminal for operating and setting the wristwatch. A multipurpose switch actuator makes continuous electrical contact between the wristwatch battery and the first contact terminal, and makes selective switching contact with the second contact terminal when actuated by a push-pull detented stem. The stem is removable when twisted using a tool so as to unseat the detent spring, so that it can be pulled from the watch frame, and is also reinsertable without disassembling the watch. The switch actuator serves various other functions, including spring biasing of the stem detent and holding the electronic circuit lead frame in the watch frame.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to an electronic wristwatch with a manually operated stem operating a switch actuator inside the watch to control its operation, and more particularly to a wristwatch in which the stem may be removed from the wristwatch and reinserted without disassembling the watch. Such watches include an internal electronic circuit and a battery supplying power to the circuit. The circuit generally includes a quartz crystal timebase, an integrated circuit with a frequency divider chain for supplying low frequency timekeeping pulses, and means to display the time either by actuating segments on an electrooptic display, or by operating a motor and gear train to drive the hands of the wristwatch. Although the invention will be described in connection with the latter type of timekeeping display in the context of a quartz analog wristwatch, the invention is equally applicable to a timepiece with an electrooptic display. 
     Manually operated crowns with stem detenting springs for holding the stem in selected axial positions and permitting axial movement of the stem against spring pressure provided by a detenting spring are well-known in the art. Examples are illustrated in U.S. Pat. Nos. 3,678,682 and 3,707,840, both issued to Miyasaka; U.S. Pat. No. 4,034,553 --Wuthrich, 4,228,647 --Yajama, and 4,363,554 --Schaffner et al., these being merely exemplary. In such stem detenting devices, the grooves in the stem between detenting surfaces are circumferential and hence there is no way to remove the stem without disassembling the watch, so that the detent spring can be detached. 
     The prior art also includes push button switch actuators for electronic wristwatches, which have only one normal axial position and are pushed against a spring bias, examples being shown in U.S. Pat. No. 3,783,607 --Feurer, U.S. Pat. No. 4,031,341 --Wuthrich et al., and U.S. Pat. No. 4,400,095 --Namyslo. 
     It is also well-known in the art to manipulate an external crown to operate internal stem-detented switch actuators for electronic wristwatches, as are illustrated in U.S. Pat. Nos. 3,526,088 --Meitinger, 4,031,341 --Wuthrich et al., and 4,536,095 --Wuthrich et al., all assigned to the present assignee. The last named Wuthrich patent 4,536,095  employs a rocking contact switch with a detented stem comprising semicircular detent grooves on one side of the stem and a flat surface on the other side of the stem. The stem is removable by inserting a tool and relieving the spring pressure by actuating extension arm on the detent rocker contact spring. 
     In order to reduce the manufacturing cost of an electronic wristwatch, it is desirable to have as few parts to be assembled as possible and for each of the parts to perform several functions. The parts are preferably designed to facilitate assembly and disassembly. 
     Accordingly, one object of the present invention is to provide an improved electronic wristwatch with a detented stem and switch actuator. 
     Another object of the invention is to provide an improved detented stem which may be manually actuated without danger of it coming out of the watch, but which may be removed and reinserted at repair facilities without disassembling the wristwatch. 
     Still another object of the invention is to provide an improved internal switch actuator for selectively operating the circuit of an electronic wristwatch. 
     Another object of the invention is to provide an simplified removable stem and switch actuator for an electronic wristwatch having a minimum number of parts. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the invention is practiced by providing a removable stem and switch actuator assembly for an electronic wristwatch of the type having a frame, an electronic circuit including at least first and second contact terminals, and an energy cell disposed in the frame. In its simplest form, a cylindrical stem which is slidably and rotatably disposed in the watch defines a first deep lateral detent groove and a second shallow lateral detent groove with inclined detenting surfaces therebetween. A conductive switch actuator mounted in the watch frame includes a detent portion adapted to fit in said grooves, at least one electrically conductive spring portion biasing the detent portion into the grooves, and a switch contact portion selectively making electrical contact when the stem is actuated by an external crown to place the detent portion in the deep lateral groove. In the preferred embodiment, the switch actuator has a member which makes continuous electrical contact between the battery and the first battery contact terminal on the electronic circuit, and makes selective contact with the second switching contact terminal on the electronic circuit. 
    
    
     DRAWING 
     The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of practice, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a plan view of a quartz analog wristwatch movement illustrating the preferred embodiment of the invention, 
     FIG. 2. is a plan view of the electronic circuit including lead frame and quartz crystal, 
     FIG. 3 is a side elevation view of the stem and crown assembly, 
     FIG. 3a is a cross-section taken through lines A--A of FIG. 3, 
     FIG. 3b is a cross-section taken through lines B--B of FIG. 3, 
     FIG. 4 is a plan view of the switch actuator, 
     FIG. 5 is an end elevation of the switch actuator together with portions of the stem, battery, and contact terminals, 
     FIG. 6 is a projected end view of the detent and switch contact portion of the switch actuator, together with portions of the stem and contact terminal 
     FIG. 7a is an elevation drawing of the stem and portions of the switch actuator with the stem in the &#34;in&#34; position, 
     FIG. 7b is the same as FIG. 7a, but illustrating the stem in an &#34;out&#34; position, 
     FIG. 7c is the same as FIG. 7a, but with the stem rotated 180 degrees for removal, and 
     FIG. 7d is the same as FIG. 7a, but with the stem removed and shown in the position for insertion. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1 of the drawing, a quartz analog wristwatch movement includes a plastic frame 1. Other parts of the movement include a stepping motor having a rotor 2 driving a center wheel 3 when actuated by pulses supplied to motor coil 4. Other elements (not shown) include a gear train and time indicating hands. 
     The frame includes a circular recess adapted to receive a button-type battery or energy cell 5 with a negative center terminal 5a and with its peripheral edge 5b serving as the positive terminal. An electronic circuit, shown generally as 6 comprises an encapsulated lead frame assembly 7 with electrically conductive extending metal strips such as 7a. Discrete electrical components include a quartz crystal 8 and capacitor 9. The electronic circuit 6 is a separate unit which can be inserted into a recess in watch frame 1 and is adapted to be held in place on one end by the switch actuator in a manner later to be described. 
     The foregoing elements comprise conventional elements in a quartz analog electronic wristwatch. The present invention concerns an improved switch actuator shown generally at 10 and a removable stem shown generally at 11 which cooperates with switch actuator 10. 
     Referring now to FIG. 2, the electronic circuit 6 is a separate subassembly comprising lead frame 7, quartz crystal 8 and capacitor 9. The lead frame 7 is an encapsulant embedding an integrated circuit and having conductive metal spring strips such as 7a protruding from the encapsulant and connected internally to the circuit elements. Conductive strips 7a serve in some cases as terminals for attaching the discrete elements, such as crystal 8 and capacitor 9, directly to the strips. The strips are also shaped to serve as battery contact terminals and switching contact terminals in a manner which is relevant to the present invention. 
     More particularly, lead frame 7 includes a negative polarity battery contact terminal 12, a positive polarity battery contact terminal 13, and a switching contact terminal 14. The circuit is arranged in accordance with polarity conventions often employed in wristwatches so that the positive connection is common or grounded to the wristwatch case, while the negative connection is the V ss  connection. Accordingly, contact terminal 12 is shaped to contact directly on the battery positive terminal 5a. Power is supplied to the circuit when the negative battery connection is made to contact terminal 13. The circuit is also arranged so that when switching contact terminal 14 is connected to ground (positive battery connection), the watch changes from a normal timekeeping to a setting mode, in which the stepping motor is actuated at a high speed to rotate the hands for setting the watch. The particular type of setting or switching accomplished by the switching contact terminal 14 is not important to the present invention. 
     Reference to FIG. 3 and the cross-section FIGS. 3a and 3b illustrate the removable stem assembly shown generally as 11. The assembly comprises a generally cylindrical stem element 15, a crown 16 press-fit over the end of stem 15, and an O-ring sealing gasket 17 disposed in a circumferential groove in the cylindrical stem element 15. The stem 15 includes a large diameter section 15a, an intermediate diameter section 15b and a small diameter section 15c with a pointed end 15d. Of particular importance to the present invention, the intermediate cylindrical portion 15b includes a first deep lateral groove 18 and second shallow lateral groove 19, separated by inclined detenting surfaces 15e, 15f. 
     Reference to FIGS. 3a and 3b illustrate that the term &#34;lateral groove&#34; is used as a particular definition in this application to distinguish it from the usual circumferential groove commonly found in watch detenting stems. Although the bottoms of the grooves 18 and 19 are preferably flat (as formed by a chord), they may also be arcuate (concave or convex) to fit the particular type of detenting element used with them. 
     The crown 16 is selected to be of a small diameter, since the normal operation of the stem by the wearer of the wristwatch is in an axial direction --&#34;in&#34; or &#34;out.&#34; The crown is only intended to be rotated for removal of the stem using a tool by an experienced repairman. 
     FIG. 4 shows the plan view of the switch actuator 10, while FIGS. 5 and 6 indicate side and end projections respectively of switch actuator 10, showing its cooperation with other elements of the watch. 
     Referring to FIG. 4, actuator 10 comprises a battery contact and spring biasing arm 10a, a central sinuous body 10b bent generally at right angles to member 10a, and a lead frame contact extension arm 10c. The arm 10a terminates in a sliding battery contact edge 10d (see also FIG. 5) on one end and a detent portion 10e and switch contact portion 10f (see also FIG. 6) on the other end. 
     FIGS. 5 and 6 illustrate the cooperation of switch actuator 10 with other elements. In FIG. 5, extension 10c is seen making continuous spring biased contact against lead frame battery contact terminal 13. This also serves to hold the electronic circuit assembly 6 in the watch frame (FIG. 1). 
     The termination 10d of arm 10a makes electrical contact with the edge 5b of the watch battery. This provides a fulcrum for spring biasing the arm, as well as electrical contact with the battery. 
     As shown in FIG. 6, the cylindrical stem element 15b is disposed adjacent the detent edge 10e. The springiness of arm 10a and its contact with the battery causes the detent portion 10e to be biased against the stem and into the lateral grooves 18 and 19 in the stem depending upon its axial position. 
     As indicated in FIG. 6, the edge 10f of actuator spring is spaced from lead frame arm 14 when the detent 10e is in the shallow groove 19. When the detent is in the deep lateral groove, edge 10f makes electrical contact with switching contact terminal 14, thereby constituting electrical switching means operated by actuator 10 when the stem is axially moved. 
     OPERATION OF THE INVENTION 
     Referring to FIGS. 7a through 7d, the operation of the invention will be illustrated. 
     FIG. 7a shows the electronic wristwatch in its normal operating position with spring detent portion 10e resting in the shallow groove 19 and the stem in its axially inmost position. The switching contacts are open and the positive battery terminal 5b is connected to the lead frame contact terminal 13 via the conductive actuator element 10. 
     FIG. 7b shows the stem pulled to its out position, whereupon the spring detent 10e moves into the deep lateral groove 18, allowing contact between switch actuator edge 10f and lead frame contact terminal 14 (see FIG. 6). This is the time setting mode of operation by a person wearing the wristwatch. Rotation of the stem is intentionally prevented by using a small diameter crown. A tool is required to supply sufficient torque for removal of the stem. 
     Reference to FIG. 7c shows how the stem is removed. A tool is applied to partially rotate crown 16 (180 degrees), thereby raising detent portion 10e onto a smooth surface of the stem unseating it from the lateral groove. This permits unobstructed removal of the stem without disassembling the watch. 
     Reference to FIG. 7d shows that the stem may then be reinserted and guided by the pointed end 15d and other inclined surfaces back into the normal operational position of the shallow lateral groove 19. 
     The spring force of arm 10a is selected to be weak enough to permit manual axial movement of the stem but strong enough, when taking the diameter of the crown into consideration, to prevent manual rotation and unseating of the detent portion of the actuator from the grooves without the assistance of a tool. In other words, by suitable selection of length and stiffness of spring arm 10a, together with diameter of crown 16, one can make manual twisting of the crown preventable, e.g. a stiffer, shorter spring arm and a smaller diameter crown requiring more torque than the normal person can supply with his/her fingers. Yet a tool such as a pair of pliers can supply sufficient torque to twist the stem so that it can be removed. 
     While there has been described what is to be considered to be the preferred embodiment of the invention, other modifications will occur to those skilled in the art, and it is desired to secure in the appended claims all such modifications as fall within the true spirit and scope of the invention.