Electronic clock having synchronized analog and digital displays

A watch includes a quartz-controlled electronic drive circuit for the control of the clockwork mechanism of a pointer-driving system for analog display of the time of day, and a digital read-out unit and control circuit for the display of additional data such as month, day of the month, day of the week, and the like. A synchronizing unit is located between the analog and digital systems to provide a synchronous link between the time of the day and the digitally displayed data. This synchronizing unit is coupled with the pointer-driving clockwork mechanism and generates a synchronizing pulse which is derived from the clockwork, preferably at a rate of one pulse per 24 hours. The synchronizing pulse is fed into the display control circuit to synchronously advance the digital read-out of the month, day of the month and day of the week, for example.

BACKGROUND OF THE INVENTION 
The present invention relates to an electronic clock, and more particularly 
to a battery-powered quartz crystal wrist watch having a quartz oscillator 
circuit and a frequency divider circuit for supplying control pulses to a 
pointer-driving clockwork mechanism for the analog indication of at least 
hours and minutes. The wrist watch to which the present invention pertains 
also includes an electronic digital display unit, for the display of 
additional data such as month, day of the month, day of the week and the 
like, a display control circuit for driving the digital display unit, and 
manually operated positioning devices for setting or correcting the analog 
and digital displays. 
British Pat. No. 1,462,898 discloses a clock of the previously mentioned 
type wherein the pointer-driving system, which operates one hour and one 
minute hand, and the digital display unit, which displays additional data 
such as month and day of the month, are each controlled by pulses which 
are derived from a frequency divider. This arrangement has a disadvantage 
in that each display system must be individually set or corrected because 
a manual adjustment of the pointer-driving clockwork mechanism does not 
result in a simultaneous adjustment of the digital read-out system. 
OBJECT AND BRIEF SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a clock 
having the previously mentioned features and further including a 
synchronous link between the analog display unit and the digital read-out 
unit. 
The synchronizing arrangement provided by the present invention insures 
that the digitally displayed data will be displayed and advanced 
synchronously with the time of the day. This synchronous link is 
accomplished by deriving the pulses for the advance of the digitally 
displayed data directly from the cyclic motion of the pointer-driving 
clockwork mechanism. A forced link is established between the 
pointer-driving clockwork mechanism and the switching elements of the 
synchronizing arrangement to generate a synchronizing pulse. When these 
elements are arranged in a predetermined position a display-advancing 
pulse can be generated at a midnight-marking point in time. This timed 
pulse occurs whether the drive of the pointer-driving clockwork mechanism 
is continuous, i.e. in the normal course of the time-keeping operation of 
the clock, or discontinuous due to a manual correction of the analog 
time-display unit.

DETAILED DESCRIPTION 
The clock illustrated in FIG. 1, for example a quartz crystal wrist watch, 
includes, within a casing 1, an analog display system 2, a digital 
read-out unit 3, a quartz oscillator 4, a display-setting unit 5, and an 
integrated display control circuit 6. The display control circuit 6 
includes a quartz oscillator circuit 7 for control of the quartz 
oscillator 4 and a frequency divider circuit 8 connected in series with 
the oscillator circuit 7. The display control circuit 6 also includes a 
conventional control logic circuit 9, several display position selection 
and correction control circuits 10, 11, 12, 13, and a logic test circuit 
14. The clock also includes a synchronizing unit 15. 
The analog display system 2 comprises a pointer-driving unit including a 
stepping motor 16, a pointer-driving clockwork mechanism 17 which is 
driven by the motor 16, an hour hand 18, a minute hand 19, a second hand 
20 and a calibrated face (not shown). The stepping motor 16 is connected 
with the output terminal of the frequency divider circuit 8. The stepping 
motor 16 is controlled by output pulses having a frequency of 1 cycle per 
second, so that the second hand 20 is advanced by means of the clockwork 
mechanism once each second. 
The digital read-out system 3 can be a fluid crystal display unit having at 
least five display positions 21 which are arranged adjacent one another. 
It is also within the realm of the present invention to use an 
electrochromatic, luminous-diode or similar type of display in place of 
the fluid-crystal display unit. The digital display positions 21, together 
with an optical separator 22 in the form of a dash or a colon, will allow 
the selective digital display of the following real time related 
information: data and month, day of the week in a preselected language or 
one of a number of other selectively available languages, date of the 
month, chronographic displays, zero time count, elapsed time, stopped 
time, etc. It is also feasible, by structuring the display control unit 6 
in an appropriate known manner, to utilize the display positions 21 for 
the display of additional functions such as specific points in time to be 
remembered, appointments to keep, specially computed figures and the like. 
Also integrated in the display control circuit 6 is a battery condition 
control circuit 23 which generates a signal when the battery voltage drops 
below a certain, predetermined level. The signal generated by the battery 
control circuit 23 is transmitted to one of the display positions 21 where 
it causes one or more of the display segments to flash intermittently. It 
is also possible to inform the user of the watch of low battery output 
potential by means of some other signal, such as an audible signal, for 
example. 
The control pulses for the operation of the fluid-crystal display unit 3 
are derived from the frequency divider circuit 8 and fed by means of 
control channels into the control logic circuit 9 where they are processed 
and transmitted to the individual display positions 21. The display 
setting unit 5 includes several switches which can be manually actuated by 
means of a plurality of push buttons 24, 25, and a rotatable spindle 26 
which can be set to various positions. The switches and spindle interact 
with the display position selection and correction control circuits 10, 
11, 12, 13 and with the logic test circuit 14 to adjust and test the 
operation of the display unit segments. 
The adjusting spindle 26 can be radially pulled from its normal illustrated 
position to an outer position. Pulling the spindle 26 to the outer 
position closes a reset contact 27 which is connected with the correction 
control circuit 10. The closing of this reset contact 27 suppresses the 
transmission of pulses from the frequency divider circuit 8 to the 
stepping motor 16 and the fluid-crystal display unit 3 while information 
is being entered into the display control circuit 6. When the spindle 26 
is in its outer position, it is also possible to correct the positions of 
the minute hand 19 and the hour hand 18 in a conventional manner by 
turning the adjusting spindle 26. When the adjusting spindle 26 is 
returned to its normal position, pulses will again be fed into the 
stepping motor 16 and the previously suppressed digital read-out will 
again appear at the fluid crystal display unit 3. 
The adjusting spindle 26 also interacts with a selection switch 28 and a 
testing switch 29 of the display setting unit 5. The testing switch 29 can 
be closed by turning the adjusting spindle 26 while in its normal 
position. This switch 29 is connected to the logic test circuit 14 and 
serves in conjunction with this test circuit to check the function of the 
display control circuit 6 and the control logic 9. The tested circuits can 
be connected to a measuring device (not shown) by way of test input leads 
30 and 31. 
The selection switch 28 can be closed by pushing the adjusting spindle 26 
from its normal position to an inside position. The closing of the 
selection switch 28, which is connected with the display-selection 
switching circuit 11, results in suppression of the day and date readout 
on the fluid crystal display unit 3 and a different piece of information, 
such as the zero display of the elapsed time function, can be displayed. A 
repeated pressing of the adjusting spindle 26 would restore the date and 
day of the week read-out. 
The elapsed time function is triggered by a first push button 24 which, 
when actuated, closes a trip-switch 32. This latter switch 32 is connected 
with a chronographic control circuit 13. The first actuation of the push 
button 24 causes the initiation of the timing operation, with running time 
being indicated in minutes, seconds and fractions of a second by the 
individual display digits 21 of the fluid crystal display unit 3. A second 
pressing of the push button 24 stops the timing operation and the elapsed 
time is then shown on the fluid crystal display unit 3. A third pressing 
of the push button 24 will reset the counters and the memory of the 
chronographic control circuit 13 and the fluid crystal display unit, 
wherein all numeral display digits 21 will then read zero. 
A second push button 25 interacts with a display selection switch 33 which 
is connected with the display-selection and correction control circuit 12. 
Beginning with a read-out of the day of the week and the date, a first 
brief pressing of the push button 25 will cause the suppression of this 
read-out and switches the display to a numerical read-out of the month. If 
this first pressing is maintained for a relatively long period of time, 
the new display, i.e. read-out of the month, will be automatically 
adjusted at a fixed correction frequency, for example 1 cps, derived from 
the frequency divider circuit 8. 
A second, brief pressing of the push button 25 results in suppression of 
the numerical display of the month and switches the display to a fully 
numerical read-out of the date, showing month and day of the month, for 
example 12-23. If this second pressing is maintained for a period of time, 
the numerical day, shown by this new read-out, is then automatically 
corrected by a fixed correction frequency, for example 1 cps, again 
derived from the frequency divider circuit 8. 
A third, brief pressing of the push button 25 results in suppression of the 
numerical read-out of the date and switches the display to abbreviations 
of the languages which can be used for the days of the week, for example 
"DT" for German, "FR" for French, "EN" for English, "IT" for Italian, 
"SP" for Spanish and "PO" for Portuguese. If this third pressing of the 
push button 25 is maintained for a period of time, the display unit 3 will 
automatically cycle through the abbreviations of the languages which can 
be used for the days of the week at a frequency derived from the frequency 
divider circuit 8, until the button 25 is released. A fourth, brief 
pressing of the push button 25 will then cause the display to switch from 
the previous language read-out to a read-out of the day of the week and 
the date of the month, with the day of the week appearing in the 
abbreviation of the selected language. If this fourth pressing of the push 
button 25 is maintained for a relatively long period of time, the read-out 
of the day of the week is corrected at the fixed frequency derived from 
the frequency divider circuit 8, until the correct day of the week appears 
on the fluid crystal display unit 3. 
A fifth, brief pressing of the push button 25 results in a return to the 
original read-out, showing the day of the week in a preselected language 
together with the day of the month. 
The synchronizing unit 15 has its input terminal connected to the 
pointer-driving clockwork mechanism 17 and its output terminal connected 
to the display control circuit 6. The synchronizing unit 15 is designed 
such that synchronizing pulses derived from the cyclic motion of the 
clockwork 17 can be fed into the display control circuit 6, preferably at 
a rate of one pulse per 24 hours, to advance the digital read-outs for the 
month, day of the month and day of the week. 
FIG. 1 illustrates a first embodiment of a synchronizing unit 15 having a 
switching wheel 34 and a pinion 35 which is mated with and driven by the 
pointer-driving clockwork mechanism 17 by means of a step-down gearing 36. 
This step-down gearing 36 is proportioned in such a manner that the 
switching wheel 34 will perform one single rotation per day. The 
synchronization unit 15 also contains a contact arrangement which closes 
at least one switching path 37 leading to the display control circuit 6, 
for the purpose of generating a display-advancing pulse. 
The switching wheel 34 carries a radially protruding pin 38 which interacts 
with the movable contact of a switch 39 connected to one pole of a 
battery. In the illustrated embodiment, the negative pole of the battery 
is connected to the movable contact and forms an integral part of the 
contact arrangement. The pin 38 is located on the switching wheel 34 in a 
position relative to the pointer-driving clockwork mechanism 17 such that 
the switch 39 will be closed for a short period of time in the course of 
continuous operation of the clock. This closure takes place once per day, 
preferably at midnight, to thereby generate a switching pulse. This 
switching pulse if fed into the display control circuit 6, and is 
transformed into a display-advancing pulse which is then transmitted to 
the fluid crystal display unit 3, with the result that the date is 
advanced each time by one unit. 
FIG. 2 illustrates a second embodiment of the synchronizing unit 15. The 
switching wheel 34 is made of insulative material and carries at its 
circumference a contact surface 40, which serves as a contact bridge. The 
contact arrangement of the synchronizing unit 15 comprises three mating 
contacts 41, 43, 45. The first mating contact 41 is connected to the set 
input terminal S of an RS flip-flop 42. The flip-flop 42 is integrated in 
the display control unit 6. The second central contact 43 is connected to 
the negative pole 44 of a battery. The third mating contact 45 is 
connected to the reset input terminal R of the RS flip-flop 42. These 
three mating contacts 41, 43, and 45 co-act in pairs with the contact 
surface 40 of the switching wheel 34 to generate two time-staggered set 
and reset pulses which are fed to the RS flip-flop 42. The contact surface 
40 is arranged on the switching wheel 34 in a manner relative to the 
pointer-driving clockwork mechanism such that, shortly before the 
generation of a display-setting pulse, the two mating contacts 41 and 43 
will be connected with each other by way of the contact surface 40 and 
thereby set the RS flip-flop 42. When the switching wheel 34 continues to 
rotate in the direction of the arrow 46, the two mating contacts 43 and 45 
will be connected with each other by way of the contact surface 40 at the 
precise moment required for the generation of the display-setting pulse, 
e.g. midnight. The location of the leading edge of the contact surface 40 
at this point in time is marked by a dot and dash line 47 in FIG. 2. A 
switching pulse is thereby produced to be fed into the reset input 
terminal R of the RS flip-flop 42 to reset the flip-flop. The signal which 
is present at the false output teminal Q of the RS flip-flop 42 will then 
be presented to the circuitry of the display control circuit 6 in the form 
of a display-setting pulse, to thereby advance the day of the week and the 
date shown on the fluid crystal display unit 3 by one unit. 
It will be apparent from the preceeding description that the digitally 
displayed values are advanced synchronously with the displayed time of 
day. This advancement applies to the continuous operation of the clock as 
well as to the case of a correction of the pointer position in a forward 
direction beyond the midnight switching time point. 
The synchronizing arrangement illustrated in FIG. 3 allows the correction 
of the displayed clock time to take place in a forward or a reverse 
direction by generating either a forward or a reverse display-setting 
pulse in dependence upon the direction of the correction motion of the 
minute hand 19 beyond the switching time point. The synchronizing 
arrangement of this embodiment includes two leaf spring contacts 48 and 49 
which are arranged side-by-side and which are connected with the positive 
pole of the battery. The arrangement further includes two mating contacts 
50, 51 which are arranged on the switching wheel 34. These two mating 
contacts 50, 51 are slightly offset relative to each other when viewed in 
the direction of rotation of the switching wheel 34. 
Each of the two mating contact surfaces 50 and 51 respectively is further 
connected with one input terminal 52 and 53, respectively, of a reversible 
control logic 54. This control logic 54 has two output terminals. The 
first output terminal is connected to the UP input terminal 55 and the 
second output terminal is connected to the DOWN input terminal 56 of an 
UP-DOWN counting unit 57. The counting unit 57 controls the advance of the 
digital read-out. The reversible control logic 54 includes two flip-flop 
units 58 and 59 which are controlled by a logic circuit consisting of 
logic gates 60, 61, 62 and 63. The reversible control logic 54 and the 
UP-DOWN counting unit 57 are components of, and are integrated in, the 
display control circuit 6. 
Due to the lateral stagger of the mating contact surfaces 50 and 51 on the 
switching wheel 34, and in conjunction with the two spring leaf contacts 
48 and 49, two time-staggered pulses are generated when the midnight 
switching time point is crossed. The relative phase shift of these two 
pulses is evaluated in the reversible control logic 54 and either a 
forward or a backward counting pulse will be fed into the UP-DOWN counting 
unit 57, depending on the relative position of the pulses. 
This arrangement insures that the analog display of the time of the day and 
the digital read-out showing the day of the week and the date will remain 
synchronous with each other not only in the course of the normal 
time-keeping operation of the clock or in the case of a forward correction 
of the analog display, but also in the case of a reverse correction of the 
analog display beyond the midnight switching time point. If a reverse 
direction correction movement of the minute hand 19 crosses the switching 
time point, the reversible control logic 54 will recognize such movement 
as being a reverse direction correction, and a counting pulse will be fed 
into the DOWN input terminal 56 of the UP-DOWN counting unit 57. This will 
result in a set back by one unit of the day of the wekk and the date shown 
on the fluid crystal display unit 3. 
The synchronous coupling of the analog time display with the digital 
read-out of the date and the day of the week is accomplished by the 
synchronizing arrangement of the present invention with the use of 
relatively simple means and in an advantageous manner. The present 
invention may be embodied in other specific forms without departing from 
the spirit or essential characteristics thereof. The presently disclosed 
embodiments are therefore considered in all respects as illustrative and 
not restrictive. The scope of the invention is indicated by the appended 
claims rather than the foregoing description, and all changes which come 
within the meaning and range of equivalency of the claims are therefore 
intended to be embraced therein.