Driving mechanism for a timepiece

A driving mechanism including a stepping motor having a rotor which rotates through a certain angular interval each time the stepping motor is energized. A driving member having a plurality of radial slots is mounted for rotation about an axis and is rotated by the rotor. A driven member is mounted for rotation and includes a pin extending therefrom for engaging one of the slots as the driving member rotates and for disengaging from the one of the slots after the driving member has rotated past the certain angular interval, whereby the driven member is rotated through the certain angular interval upon energization of the stepping motor. The driving member includes arcuate peripheral portions over a limited angular extent and concentric with the axis of rotation of the driving member. The driven member includes concave arcuate portions of limited angular extend spaced about the periphery thereof. The driven member is rotatable to a position so that one of the arcuate portions is concentric with the axis of rotation of the driving member and extends along and opposite an arcuate peripheral portion of the driving member for preventing rotation of the driven member when an arcuate peripheral portion of the driving member and one of the corresponding concave arcuate peripheral portions of the driven member are opposed when the stepping motor is not energized.

BACKGROUND OF THE INVENTION 
The present invention relates to an improvement in a driving mechanism 
including a series of wheels of an electric clock to operate a clock 
pointer intermittently with a step motor. 
In a hitherto used electric clock provided with a step motor wherein the 
rotor was rotated by a definite angle in one direction at each driving 
pulse, a method was generally used in which a pointer such as a second 
hand is operated intermittently by connecting a series of gear wheels to a 
pinion directly connected with the rotor. In this method, however, since 
the movement of the rotor is transferred as it occurs, when the rotor 
moving in step at each pulse is stopped, a vibration produced by the 
inertia thereof will be transmitted to the second hand so that it is 
difficult to observe the second hand. 
Consequently, some means have been considered to resolve such a defect. One 
is a means of loading a frictional piece to a series of gear wheels to 
which the second hand is directly connected, or to make a click piece 
operate. But, as an unnecessary load is applied by either of them, it is 
necessary to enlarge the output of the step motor, which brings about a 
decrease in battery life if a battery is used. In another means where the 
inertia of the rotor is reduced as the size of the rotor should be 
minimized as far as possible, the output torque of the motor will become 
small so that there arises a disadvantage in reduced reliability. And in 
order to increase this torque characteristic, a magnetic material of high 
energy content should be used, resulting in high cost. Therefore the main 
object this invention consists in eliminating these defects. And the 
secondary object is to provide a driving mechanism in which the gear train 
beyond the driven wheel is not connected when the rotor is about to start 
its rotation so that the rotor starts under a no-load condition so that 
the starting characteristic of the rotor can be improved. And in a 
hitherto-used electric clock, in case of correcting the time, it was 
formerly needed to provide a mechanism in order to prevent the second hand 
from moving together with the second wheel prevented from rotating, 
simultaneously with pushing of the time-correcting button. Therefore the 
futher object of this invention is to remove the the requirement for this 
mechanism. 
SUMMARY OF THE INVENTION 
According to this invention, the aforementioned object has been achieved in 
the following way. Namely, a driving wheel operated by a step motor and a 
driven wheel that is connected to a timing wheel installed with a pointer 
and operated by the said driving wheel are provided, with coupling means 
including an intermittent driving mechanism for coupling the driving wheel 
or member with the driven wheel or member to rotate through an angular 
interval upon operation of the step motor and with means for fixing the 
angular position of the driven wheel or member and for preventing rotation 
of the driven member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 2 shows a cross section of FIG. 1 in column 2 is fixed on a base plate 
1, an intermediate plate 3 having a second column 2 fixed thereto is fixed 
to the said column 2 by a screw 4, and an upper plate 6 is fixed to the 
said second column 2 by a screw 7. Shafts 8,9,10 and a second hand shaft 
11 are rotatably supported by the said upper plate 6 and the intermediate 
plate 3, a minute hand shaft 12 and an hour hand shaft 13 are rotatably 
supported by the said second hand shaft 11 and the base plate 1 and are 
coaxial with said second hand shaft 11, and another shaft 14 is fitted to 
the base plate 1. To the said shaft 8 is fixed a first rotor 15 in which 
two poles are magnetized around the periphery. Also to the shaft 9 is 
fixed a driving wheel or member 17 to which a second rotor 16 is fixed and 
that is magnetized with two poles of N2,S2 corresponding to the said first 
rotor poles N1,S1. To the said driving wheel 17 are installed two pins 
17a, 17a on a straight line and two fan-shaped parts 17b, 17b at nearly 
right angles to this straight line. 
And to the shaft 10 is fixed a driven member or a star wheel 19 that is 
provided with a first pinion 18 and six radial slots or grooves 19a which 
are engaged in operation by a pin 17a of said driving wheel, as well as 
circular parts or concave arcuate portions 19b which cooperate with part 
17b. 
In a static state, as shown in FIG. 1, since one pole (e.g. N1-pole) of the 
first rotor and one pole (e.g. S2-pole) of the second rotor attracted to 
each other, the respective poles are present on a straight line connecting 
the shaft 9 and the shaft 10. Therefore, the pin of the driving wheel 17 
is positioned apart from the groove 19a of the star wheel and the 
fan-shaped part 17b is positioned adjacent the circular portion 19b of the 
star wheel periphery. 
the said second hand shaft 11 are fixed a second unit wheel 20 that is 
engaged with the first pinion 18 and a second pinion 21, and at the same 
time to the end of the second hand shaft 11 is fixed a second hand 22. 
Engaged with this second pinion 21 is an intermediate gear wheel 24 that 
is rotatable centered on the said shaft 14 and fixed with a third pinion 
23. With the said third pinion 23 is engaged a minute unit wheel 26. Said 
minute unit wheel 26 is formed in a pipe shape and rotatable centered on 
the minute hand shaft 12 having a fourth pinion 25. Said second hand shaft 
11 penetrates through the center of this pipe-shaped minute hand shaft 12, 
and at the end of the minute hand shaft 12 is fixed a minute hand 28. 
With said fourth pinion 25 is engaged a second intermediate gear wheel 30 
that is rotatable centered on the said shaft 14 and provided with fifth 
pinion 29. An hour unit wheel 31 is engaged with said fifth pinion 29, 
This hour hand shaft 13 is formed in a pipe shape, at the end thereof is 
fixed an hour hand 33, the outer diameter thereof is guided by the base 
plate 1 and furthermore, the minute hand shaft 12 penetrates through the 
center thereof. 
Next, the action of such arrangement will be described in the following: 
As mentioned previously, when there is no current in the coil L, the N1-and 
S1-poles of the first rotor 15 and the N2-and S2-poles of the second rotor 
16 are arranged on a straight line connecting the respective axes 8,9 and 
the angle thereof is about 45.degree. relative to the direction of the 
magnetic field of the coil L, When a current flows through the coil L 
under this condition, producing a S1-pole in the upper part and a N1-pole 
in the lower part as shown in FIG. 1, said first rotor 15 begins to rotate 
clockwise, thereby, since the N1-pole of the first rotor rotates 
clockwise, the S2-pole of the second rotor that is in an attractive 
relation with this rotor and starts a counterclockwise rotation following 
it. 
At this time, since the pin 17a of the driving wheel 17 to which the second 
rotor 16 is fixed does not yet fit to the groove 19a of the star wheel, 
there exists a load in the coil L only at the first rotor 15 and the 
second rotor, that is, the driving wheel 17. Thereafter, when the driving 
wheel 17 rotates at a definite angle, the fan-shaped sustaining part 17b 
is released from fitting with the circular part 19b of the star wheel at 
the same time, the pin 17a of the driving wheel fits to the groove 19a of 
the star wheel, so that the counterclockwise rotation of the driving wheel 
17 is transferred to the star wheel 19 during its clockwise rotation. 
Furthermore, this rotation is transferred to the second hand 22 by a 
well-known means, that is, through a first pinion 18 and the second unit 
wheel 20, and to the minute hand 28 through the second unit wheel 20, the 
second pinion 21, the intermediate gear wheel 24, the third pinion and the 
minute unit wheel 26, and further to the hour hand 33 through the minute 
unit wheel 26, the fourth pinion 25, the second intermediate gear wheel 
30, the fifth pinion 29 and the hour unit wheel 31, respectively. 
Thereafter, when the first rotor 15 and the second rotor 16 rotate, as 
shown in FIG. 3, up to a place exceeding a point where the lines 
connecting the respective poles (N1' and S1' and N2' in the figure) 
become parallel, then, by the attractive force between the S-pole (S1') of 
the first rotor and the N-pole (N2') of the second rotor, the respective 
rotors are made to rotate. In such a process, the pin 17a is released from 
fitting to the groove 19a of the star wheel, completing the one step 
intermittent feeding. Thereafter, the rotors are rotated up to the 
position where the poles S1' and N2' of the respective rotors come to the 
shortest distance, but as the both rotors have inertia, they are subjected 
to oscillation. However, the said oscillation is not transferred to the 
star wheel 19, because the oscillation occurs within an angle narrower 
than the distance that the pin 17a has to travel to fit the groove 19a. 
After finishing such an oscillation, the first rotor 15 and the second 
rotor 16 continue to be at rest until a succeeding pulse of opposite 
direction flows through the coil L at the condition where the respective 
poles S1',N2' positioned with the shortest distance therebetween. It is 
remarked that in this embodiment, the angle up to fitting between the pin 
17a of the driving wheel and the groove 19a of the star wheel is about 
36.degree., but by setting the said angle wider than the width of 
oscillation of the second rotor 16, the object of this invention can be 
accomplished. FIG. 4 shows another embodiment, wherein, although the 
synchronous motor and the intermittent feeding mechanism are different 
from those of the first embodiment, the series of wheels beyond a second 
hand wheel 12.degree. is the same as in the first embodiment. 
A rotor 116 with two magnetized N,S poles around its periphery, a driving 
wheel 115 and a circular disk 117 are fixed to a shaft 109. Said driving 
wheel 115 has two sets of figure-place changing teeth 115a, and the 
circular disk 117 has a circular part 117b and a notched part 117a to be 
mentioned later. L is a coil to which an alternating current is applied, 
and an iron core 107 is inserted into this coil. And two sets of stators 
108a, 108b are fixed to said iron core 107 by means of screws 105, and 
semicircular magnetic poles for the rotor 116 are formed in the stators as 
the center of the semicircle of these magnetic poles is different from the 
center of the rotor, as shown in the figure, the rotor is, in a static 
state, stopped at the position where the said magnetic poles and the poles 
of the rotor are located closest to each other. On the other hand an idler 
119 having toothless parts 119b and teeth 119a at eight positions and a 
first pinion 118 are fixed around the whole circumference of a shaft 110. 
And in a static state, the driving wheel 115 and the circular disk 117 are 
at a position where the figure feeding action is not performed as shown in 
the figure in correspondance with the stopping position of said rotor. 
Conversely, the toothless parts 119b of the idler 119 and the circular 
part 117b of said circular disk 117 correspond to each other, and the two 
teeth 119a of the idler existing at both sides of the toothless parts fit 
with said circular part 117b. And, similarly as in the first embodiment, 
the second unit gear wheel 120, the second pinion 121 and the second hand 
122 are fixed to a shaft 111. Since the series of wheels beyond said 
second pinion is constructed in an entirely similar manner as in the first 
embodiment the details thereof are omitted here. 
In the first place, in a static state when there is no current flowing 
through the coil L, as the poles S, N of the rotor 116 are stopped at a 
position closest to the inner surface of the stators 108a, 108b, the rotor 
116 is caused to stop at an angle of about 45.degree. the center of the 
magnetic fieled of each stator. 
In this state when a current flows through the coil L in the direction such 
that an N-pole is produced in the stator 108a and an S-pole is produced in 
the stator 108b the rotor 116 begins to rotate counterclockwise. At this 
time, since the figure-place raising tooth 115a is in a position not to 
fit with the tooth 119a of the idler, only the driving wheel 115 and the 
circular disk 117 start their rotation and the series of wheels beyond the 
idler 119 remains at a standstill. In this way when the roller 115 rotates 
a definite angle, the fitting between the circular disk 117 and the tooth 
119a of the idler 119 is released, and at the same time the figure-place 
raising tooth 115a of the driving wheel 115 fits with the tooth 119a of 
the idler. Therefore, the rotation of the rotor 116 is transferred 
thereafter to the series of wheels beyond the idler 119. And, when the 
rotor 116 is rotated further by a specified angle, the fitting of the 
figure-place raising tooth 115a of the driving wheel with the tooth 119a 
of the idler is interrupted, and the circular part 117b of the circular 
disk 117 and the tooth 119a of the idler are fitted again, causing the 
rotation of the idler 119 to stop. The rotation of the idler 119 thus 
transferred at a definite angle is transferred to the second hand wheel as 
a rotation angle corresponding to one second on the dial. And, after the 
idler 119 is stopped, the rotor 116 is still rotatable and continues its 
rotation up to the position removed from the initial position by 
180.degree., where the poles opposite to those in the initial position 
come to the closest position to the poles of the stator respectively. This 
state of standstill is kept until a current of opposite direction to the 
case previously mentioned is applied to the coil L.