GB2034936A - Analog quartz wristwatch movement - Google Patents

Abstract

An analog quartz wristwatch movement comprises a base plate (10) with a recess to receive a power source (battery) (29), an electromechanical transducer (stepping motor) having a coil (22), a wheel train arranged generally centrally and around part of the periphery of the battery (29), a circuit board (12) carrying electronic components, and a battery retaining spring (37) (serving as the negative contact of the battery) which is secured (by a screw 38) at a position between the yoke (24) of the electromechanical transducer and the battery (29), the position at which said retaining spring (37) is secured being located closer to the centre of the wristwatch movement than one of the positions at which said electromechanical transducer is secured (by a screw 26a). A long motor coil (22) can thus be accommodated parallel to the base plate, without restricting the battery space. The screw (38) holds the spring (37) in contact with a conductive plate which is located on the circuit board (12) above the yoke (24). <IMAGE>

Description

SPECIFICATION Analog quartz wristwatch movement BACKGROUND OF THE INVENTION This invention relates to movement constructions for an analog quartz wristwatch, and more particularly to a watch module construction by which an analog quartz wristwatch whose timepiece movement has a thin and well-designed external form in provided.

In analog quartz wristwatches equipped with a stepping motor as an electromechanical transducer, the major portion of the space is occupied by the stepping motor and the other major structural components of the timepiece, namely the power source battery, drive circuitry, circuit board and a setting mechanism for a controlling purpose. In designing timepieces which are thin and compact, the overlapping of these structural timepiece components is naturally avoided to the greatest possible extent. How the overlapping of these components is minimized and how they are reduced in thickness and miniaturized in the limited confines of a wristwatch are important questions in realizing analog quartz wristwatches which are thin and compact. On the other hand, a large sized battery with a large electrical capacity should be used in order to provide the timepiece with a battery that is longlived.This, however, makes it difficult to reduce the size and thickness of the timepiece. Conversely, employing a small battery with a small electrical capacity with the intent to decrease timepiece size and thickness is a problem since it shortens the lifetime of the timepiece battery. Thus, these proposals are reciprocally related. To satisfy the need for thinner and more compact timepieces and extended battery lifetime in view of this reciprocal relationship, there is intense demand for achieving this end by reducing the power consumed by the transducer such as a stepping motor, this being accomplished by attempting to improve the conversion efficiency of the transducer which consumes a comparatively large amount of power in a timepiece.

SUMMARY OF THE INVENTION According to the present invention, there is provided in a movement construction for an analog quartz wristwatch powered by a battery, comprising: a base plate having its one side formed with a battery accommodating recess at a first area closer to an outer periphery of said base plate; a wheel train bridge mounted on the one side of said base plate at a central portion of said base plate; a wheel train disposed between said base plate and said wheel train bridge and arranged around an outer periphery of said battery; a circuit board mounted on the one side of said base plate at a second area opposite to said first area with respect to said central portion; a battery retaining spring secured to the one side of said base plate for retaining said battery in place; and an electromechanical transducer including a driving coil extending parallel to a side surface of said circuit board, said driving coil including a core having their terminal ends secured to the one side of said base plate at positions closer to the outer periphery of said base plate; the position at which said retaining spring is secured being located closer to said central portion of said base plate than one of said terminal ends of said core of said driving coil.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a plan view showing a preferred embodiment of a movement structure for an analog quartz wristwatch according to the present invention, and Figures 2, 3 and 4 are cross-sectional views showing essential portions of the structure shown in Fig. 1.

DESCRIPTION OF THE PREFERRED EMBODI MENTS In Fig. 1, there is shown a preferred embodiment of a movement structure for an analog quartz wristwatch according to the present invention. The movement structure comprises a base plate 10 and a synthetic resin circuit board 1 2 mounted on one side of base plate 1 0. The circuit board 1 2 carries thereon a quartz crystal vibrator 13, trimmer capacitor 14, integrated circuit chip 1 5 and a temperature compensating capacitor 1 6. Circuit board 1 2 that mounts these elements is molded on resin so as to accommodate the integrated circuit chip 1 5 as well as a lead plate 21 that is connected through threaded tubes 18, 19, and 20 and partially embedded in the circuit board.A screw 1 8a secures the quartz crystal vibrator 1 3 by way of a quartz crystal retaining spring 1 3a, and screws 1 9a, 20a secure the temperature compensating capacitor 1 6 to the circuit board 1 2 through lug plates 19b, 20b.

Since the oscillation frequency of quartz oscillators undergoes a shift owing to a change in temperature, it is quite obvious that the provision of the temperature compensating capacitor 1 6 which matches the temperature characteristics of the oscillator is necessary in order to improve timepiece accuracy.

However, mounting the temperature compensating capacitor 1 6 through a process such as soldering which requires the application of heat, as is practiced in the prior art, calls for a prolonged period of aging in view of the thermal aging characteristics of the capacitor.

This lengthens the production process. The present invention overcomes this by mounting the capacitor 1 6 through the lug plates 1 9b, 20b that are secured by tightening screws 1 9a, 20a. This contributes to shortening production time and, since the temperature com pensating capacitor 1 6 can be freely exchanged, to a much higher precision.

Reference numeral 22 designates a transducer or driving coil which is secured through the coil core 23 and yoke 24 to threaded tubes 25, 26 implanted in the plate 10. If the thicknesses of the coil core 23 and yoke 24 are reduced to make these elements thin, the result is a drop in conversion efficiency owing to an enlarged magnetic resistance. The core and yoke must therefore not be too thin. In consideration of reducing timepiece thickness an obvious method is thinning the base plate 10 which can be accomplished without lowering the conversion efficiency of the transducer. When the screws 25a, 26a are tightened, however, the threaded tubes 25, 26 are likely to rotate and fall out owing to the reduced plate thickness, particularly the portion in the vicinity of the tubes 25, 26.The present invention therefore utilizes tubes 25, 26 that are formed to include irregularly shaped flanges 25b, 26b that engage with recesses 1 0a, lOb formed in another side of the base plate 10, thereby locking the tubes 25, 26 against rotation and preventing them from falling out.

Designated at 27 is a magnetic shielding plate made of a magnetic material for protecting the coil 22 from an externally applied magnetic field. The magnetic shielding plate 27 is positioned by coil winding frames 28a, 28b and recesses 10c, 1 Od of base plate 10, and is secured to base plate 10 by screw 27a so as not to be dislodged by an externally applied impact force.

The power source battery 29 is disposed in a battery accommodating recess 1 ooh formed at an area closer to the outer periphery of the base plate 10 between the 1 2 o'clock and 3 o'clock positions to avoid the stacking of the battery and fourth wheel and pinion 30a and center wheel and pinion 30b which are located in the center of the base plate 10. This arrangement is also advantageous in that it facilitates the readability of the time display.

Specifically, if a battery hatch is disposed on the case back cover (not shown) at a position corresponding to that of the battery 29, and if a construction is adopted that allows the battery hatch to partially project from the surface of the back cover, the display surface (i.e., the dial side) of the wristwatch will be inclined toward the viewer's line of sight once it has been fastened to his wrist, thereby placing the time display in an easily readable attitude.

Disposed on the front surface of base plate 10, as is shown in the drawings, are a setting lever 32, clutch lever 33, setting lever spring 34 and reset lever 35 that constitute timepiece setting mechanism operated by a time setting stem 31. This arrangement surmounts the difficulties encountered in the prior art wherein obtaining a thin movement is difficult because the setting mechanism is provided on the back surface of the base plate 10, and is therefore effective in eiiminating the space occupied on the back side by the time setting mechanism. This space is instead provided on the front side of base plate 10 which is where the time setting components are disposed.

Since the setting components when so arranged do not exceed the height of the wheel train bridge 41 and battery 29 that decide the height of the upper surface of the movement, an overall reduction in movement thickness is achieved. Moreover, disposing the time setting components on base plate 10 in the vicinity of the time setting stem obviously makes the most effective use of space. Arranging the time setting components on base plate 10 between the 9 o'clock and 1 2 o'clock positions is desirable also in view of the fact that the battery 29 is disposed on the base plate between the 12 o'clock and 3 o'clock positions as described above.It is also necessary in consideration of function and space to dispose circuit board 1 2 close to the time setting components owing to the fact that a switch is constructed by the tip 35a of the reset lever 35 and a reset terminal 21a disposed on the circuit board 1 2. The portion of the wheel train that drives the hands of the timepiece should naturally be arranged closer to the central portion of the movement since the turning motion of the associated gears is reduced starting from a rotor 36, which is surrounded by the yoke 24, and proceeds toward the center of the movement. The connection to the terminals of the transducer coil 22 is effected by elastic contact between the terminals and the lead plate 21b from the electronic circuitry 1 5 mounted on the circuit board 12.It is necessary therefore that one edge of the circuit board 12 be close to the terminal portion of the coil 22. In order to improve the conversion efficiency of the electromechanical transducer, the coil 22 and coil core 23 of the present embodiment are made longer than the corresponding members in the prior art. In the prior art, in other words, the coil is wound on a short coil core. To obtain a prescribed conversion efficiency in such a case requires that the coil be provided with a large number of layers, a requirement that necessarily increases the number of turns. The result is that the upper layer of the coil windings gradually becomes more remote from the coil core so that the improvement in conversion efficiency per unit turn is not as great as expected as the number of turns reaches a large value. Thus, rather than providing the desired improvement, a problem arises in that the timepiece increases in thickness owing to the enlarged overall coil diameter which can be attributed to the numerous layers of coil windings.

In accordance with the illustrated embodiment, the length of coil core 23 is increased as much as possible in order to improve the conversion efficiency per unit turn and, in order to reduce timepiece thickness, the number of coil winding layers is reduced so as to decrease the diameter of the overall coil to the maximum allowable extent. However, since merely increasing the length of the coil core 23 would increase the size of the wristwatch, the present embodiment avoids this by adopting the following structure.A set screw 38 for fastening a spring 37 which is in electrical contact with the negative side of battery 29 is positioned between the yoke 24 and battery 29, the yoke 24 and coil core 23 are stacked, and a set screw 26a for securing the yoke 24 and coil core 23 to the base plate 10 is positioned closer to the outside of the movement than the set screw 38 or, conversely speaking, the set screw 38 is positioned closer to the center of the movement than the set screw 26a. This allows the disposition of a long coil core 23 without enlarging the size of the movement. Moreover, the yoke 24 is accommodated in a recess 1 0e formed in base plate 10 so as to provide a thinner crosssection.As a result, the connection between the spring 37 contacting the negative pole of the battery 29 and the lead plate 21 provided on the circuit board 1 2 is accomplished by bending the spring 37, as shown in Fig. 4, and by tightening the set screw 38 to secure the spring 37 to the lead plate 21c which is located on circuit board 1 2 above the yoke 24. This arrangement precludes any increase in thickness even though component parts are stacked. Furthermore, the spring 37 and lead plate 21 c are welded together so that there is no danger of a break in contact should the set screw 39 loosen. The battery 29 is secured by tightening down the battery retaining plates 39, 40.Battery retaining plate 39 is fastened to base plate 10 through wheel train bridge 41, and battery retaining plate 40 is secured against spurious upward movement by a shaft 42 but is capable of being freely rotated if a screw 43 is loosened. Thus, the battery is exchanged by loosening screw 43 and then rotating retaining plate 40 in the direction of arrow A shown in Fig. 1. Accordingly, since the battery contact portion 37a of spring 37 is located not at the center of the battery but closer to the side where the retaining plate 40 is provided, the battery 29 is caused to spring upward owing to the spring force of spring 37 without the need of loosening retaining plate 39. This greatly facilitates replacement of the battery.In addition, the fact that the top surface of the battery is pressed by the bent portions 39a, 40a of retaining springs 39, 40, respectively, does not allow the battery 29 to be sprung up during normal use even if the amount of force applied by spring 37 is increased. This arrangement also lessens the chances of poor contact between the spring 37 and battery 29 due to battery leakage or the like.

Thus, in accordance with the arrangement of major structural timepiece components as described above, the space occupied by a battery is enlarged, the length of a transducer coil increased, and the interconnection between the battery and circuit board is effected above the top surface of the yoke. This makes it possible to realize an analog quartz wristwatch in which there is no increase in thickness resulting from stacking of component parts, and in which battery replacement is simplified and the interconnection between the battery and circuit board perfected. The wristwatch is also thin, resistant to magnetic fields, and can be provided with a wide diversity of designs.

It will now be appreciated from the foregoing description that the present invention makes it possible to provide a movement construction for an analog quartz wristwatch powered by a battery, comprising: a base plate having its one side formed with a battery accommodating recess at a first area closer to an outer periphery of said base plate; a wheel train bridge mounted on the one side of said base plate at a central portion said base plate; a wheel train disposed between said base plate and said wheel train bridge and arranged around an outer periphery of said battery; a circuit board mounted on the one side of said base plate at a second area opposite to said first area with respect to said central portion; a battery retaining spring secured to the one side of said base plate for retaining said battery in place; and an electromechanical transducer including a driving coil extending parallel to a side surface of said circuit board, said driving coil including a core having their terminal ends secured to the one side of said base plate at positions closer to the outer periphery of said base plate; the position at which said retaining spring is secured being located closer to said central portion of said base plate than one of said terminal ends of said core of said driving coil.

Claims (4)

1. A movement construction for an analog quartz wristwatch powered by a battery, comprising: a base plate having its one side formed with a battery accommodating recess at a first area closer to an outer pheriphery of said base plate; a wheel train bridge mounted on one side of said base plate at a central portion of said base plate; a wheel train disposed between said base plate and said wheel train bridge and arranged around an outer periphery of said battery; a circuit board mounted on the one side of said base plate at a second area opposite to said first area with respect to said central portion; a battery retaining spring secured to the one side of said base plate for retaining said battery in place; and an electromechanical transducer including a driving coil extending parallel to a side surface of said circuit board, said driving coil including a core having their terminal ends secured to the one side of said base plate at positions closer to the outer periphery of said base plate; the position at which said retaining spring is secured being located closer to said central portion of said base plate than one of said terminal ends of said core of said driving coil.

2. A movement construction according to claim 1, in which said electromechanical transducer also includes two yokes connected to said terminal ends of the core of said driving core and extending toward the central portion of said base plate, and further comprising a screw secured to said base plate at a position between said battery and one of said yokes to retain said battery retaining spring in place

3. A movement construction according to claim 1 or 2, in which said first area is defined between the 12 o'clock and 3 o'clock positions.

4. A movement construction substantially as shown and described with reference to the accompanying drawings.