US3487630A - Balance mechanism for an electronic watch - Google Patents

Description

Jan. 6, 1970 P. J. FORTY 3,487,630

BALANCE MECHANISM FOR AN ELECTRONIC WATCH Filed Sept. 28, 1967 4 Sheets-Sheet 1 CIRCUIT N i 0 Plmu INVENTOR. PHILLIP J; FUR 7) Jan. 6, 1970 P. J. FORTY BALANCE MECHANISM FOR AN ELECTRONIC WATCH 4 Sheets-Sheet 2 Filed Sept. 28, 1967 Z5 Z4 Z9 Z5 28 F IG. 2

m m E V Jan. 6, 1970 P. J. FORTY BALANCE MECHANISM FOR AN ELECTRONIC WATCH Filed Sept. 28, 1967 4 Sheets-Sheet 5 w R Q Q J A m K M W M Jan. 6, 1970 P. J. FORTY 3,487,630

BALANCE MECHANISM FOR AN ELECTRONIC WATCH Filed Sept. 28, 1967 4 Sheets-Sheet 4 INVENTOR. P/l/LL/P J. FORT) United States Patent Int. Cl. G04c 3/04 US. CI. 5828 12 Claims ABSTRACT OF THE DISCLOSURE A watch is constructed with an internal source of electric power, such as a battery, an electronic circuit, a balance wheel and a hairspring. The watch also includes time indicating means, such as rotating hands, and means to transmit the power to the time indicating means. The balance wheel oscillates and provides a mechanical timebase. The impulse to drive the balance wheel is through the physical turning movement of the arm to which the outer end of the hairspring is attached, i.e., the pinning arm. An electric motor means, for example, a solenoid, turns the pinning arm. The motor means is pulsed by the electronic circuit which obtains its time control by a pick-off device associated with the balance wheel.

DESCRIPTION The present device relates to horology and more particularly to a watch driven by an internal electrical power source.

The science of horology is one of the first of the industrial arts. Watchmakers have sought, for many years, to produce timekeeping devices having greater accuracy which could be produced at a reasonable cost and be small enough to be carried.

One of the major problems in the search for timekeeping accuracy is that of position error. This problem is not found in fixed clocks, which ahe designed to be operated only in position, usuall vertically. However, the position of portable watches, including pocket and wrist watches, often changes during the day in an erratic manner. At times, particularly with wrist watches, the dial may be up, down, or tilted. The vertical force of gravity causes the watch to run slower, in certain positions, than it should.

The problem of position error has had many proposed solutions. For example, it has been suggested that the use of a high frequency, i.e., over 300 vibrations per second, battery driven tuning fork would avoid position error. This type of mechanism is delicate and expensive and is still subject to sufficient position error so that watches of this type have not received official certification as chronographs. Various more complex forms of resonators have also been proposed, but these may present difiiculties as to size, cost, power consumption and difficulty of manufacture. Watches driven by a mainspring and using a plurality of balance wheels of other types of complex compensating mechanisms have been suggested, but these have not proven to be of practical interest due to their cost, complexity and difficulty of adjustment.

It is the objective of the present invention to provide a watch which is relatively simple to manufacture, low in cost and free of position error.

It is another objective of the present invention to provide a balance wheel watch in which there is a minimum of physical interference with the free motion of the balance wheel.

In accordance with the present invention, a portable watch is provided. The watch includes a frame plate and bridge, or two frame plates, between which a balance 3,487,630 Patented Jan. 6, 1970 wheel fixed to a staff is rotatably mounted. The watch includes a source of electric power, such as an electric battery or a solar cell, and an electronic circuit. The balance wheel is connected to the inside end of a hairspring.

The outer end of the hairspring is fixed to a pinning arm. The pinning arm is connected, either directly or through gearing, to an index wheel. The pinning arm is mounted on a bearing so that it may be rotated, by the index wheel, for a full 360-degree rotation. The index wheel is turned, either directly or indirectly, by an electric motor means, such as a solenoid. The motor means is supplied with electric impulses by the circuit, which is electrically connected to the power source.

The turning of the index wheel causes, by means of its connected pinning arm, a torque on the outer end of the hairspring. This torque causes the hairspring to wind up more than it is wound, and in the same direction, due to the swing of the balance wheel. The torque is opposite to the tension in the hairspring due to its winding by the balance wheel. The imparting of torque to the outer end of the hairspring provides energy to the balance wheel and maintains the oscillation of the balance wheel. Preferably the torque is provided once for each full balance wheel swing at the instant When the balance wheel is still at one end of its swing, i.e., when it is changing direction, and all the kinetic energy from the balance Wheel is in the hair spring in the form of potential energy. The circuit is controlled, as to its timing, by a control mechanism associated with the balance wheel. For example, the balance wheel may carry one or more magnets which cooperate with a fixed coil on the frame to provide, by their interaction, a pick-off for the circuit.

Other objectives will be apparent from the following FIG. 5 is a perspective view of the said balance wheel and coil;

FIG. 6 is a diagram showing a voltagethe circuit impulse;

FIG. 7 is a block diagram of a circuit for use with the embodiment of FIG. 4;

FIG. 8 is a wiring diagram of the circuit of FIG. 7;

FIG. 9 is a perspective view of a second embodiment of the balance wheel and magnet; and

FIG. 10 is a diagram of a circuit for use with the embodiment of FIG. 9.

The watch, shown as a wristwatch in FIG. 1, includes a conventional case 1 having a back (not shown) and an integral bezel 2. A crystal 3 is fixed on the case 1 and protects the mechanism of the watch. A dial plate 4, positioned below the crystal, has a plurality of numbers 5 on its face indicating time. The seconds hand 6, minute hand 7 and hour hand 8 are attached to respective staffs or tubes driven at the center of the dial plate 4. The hands are driven by the dial train 9 consisting of a series of meshing gears and pinions. The first geared wheel 10 of the train is attached to the index wheel 11. The power for the watch is derived from a small electric dry battery cell 12 having external top contact 13. Alternatively a solar cell, a rechargeable cell or other power sources may be used. A spring 14 touches contact 13 and is attached time graph of to a wire leading to electronic circuit 16. The circuit 16 has an output wire 17 leading to the motor mechanism 18, which preferably is a solenoid having a reciprocating armature 19. The armature 19 terminates in a jewel 20 which drives the index wheel 11. A click 21 acts to keep the index wheel 11 in its correct position.

The cross-sectional side view of FIG. 2 shows the balance wheel 22 and its associated mechanism. The balance wheel 22 is fixed to the balance wheel staff 26 which rotates in top bearing 23 and bottom bearing 24. The balance wheel is shown as being the form of a flat rod, although other shapes may be used. The bottom bearing 24, which preferably is a jewel, is fixed in bottom frame plate 25. A hairspring 28 has its inner end fixed to the balance wheel staff by means of a hub 29. The outer end of hairspring 28 is fixed to the flange 30 of pinning arm 31. The inner end of pinning arm 31 is integral with, or fixed to, a bushing 32. The bushing 32 rotates in the bridge 27. The top bearing 23 is fixed in the bushing 32 and is preferably a shock-absorbing jewel arrangement.

FIG. 3 shows the function of the motor means. The motor means, preferably a solenoid 18, has a reciprocating armature 19 carrying, at its end, a jewel 20. Upon receiving a current pulse from circuit 16, the solenoid armature 19 is extended. This causes jewel 20 to move index wheel 11 one tooth in the clockwise direction. The armature is returned, after removal of current, by an internal spring (not shown). The solenoid may alternatively operate by retraction of the armature upon receipt of a current pulse. As another alternative, a stepping motor may be used providing a single step for each current pulse. The armature of the step motor would be connected to the first wheel 10 and to the bushing, either directly or through intermediate gears. A spring click 21 is used to prevent turning of the index wheel, due to shock or other causes, and to keep the index wheel correct positioned. The exact size and number of teeth of the index wheel 11 depends on the relationship of the index wheel to the balance wheel assembly. Preferably one tooth of index wheel 11 is indexed for each complete swing of the balance wheel. If the balance wheel has a frequency such that it swings five times a second, the index wheel may have 50 teeth and turn 6 times a second. However, as the tooth space determines the amount of energy imparted to the balance wheel, by determining the tuming movement of the pining arm, the tooth space also depends upon the amplitude decay, due to friction, etc., of the balance wheel and the desired working amplitude of the balance wheel. The reaction force of the oscillation of the balance wheel is transmitted, by the hairspring and the pinning arm, as a torque to the index wheel. However, click 21 retains the index wheel 11 in position in spite of the relatively small torque due to oscillation of the balance wheel. A typical balance wheel will provide a torque, through its hairspring, of only 0.16 gram centimeters. The holding force of the click 21 is determined so that it is overcome by the movement of the reciprocating armature 19 which indexes the index wheel.

Various pick-ups and circuits may be provided to correctly time the current pulse to the motor means 18. A suitable pick-up is shown in FIGS. 4 and 5 and a suitable circuit for use with that pick-up in FIGS. 7 and 8. As shown in FIGS. 4 and 5, the balance wheel 22 carries at one, or both, of its ends a set of magnets 34 and 35. If only one set of magnets is used, the balance wheel carries a counterweight at its opposite end. The magnets 34 and 35 are positioped so that they move close to a coil 36. The magnets facing the coil are the north pole of magnet 35 and south pole of magnet 34. The magnets may be small and of an inexpensive ceramic material. The interaction of the magnets 34 and 35 with coil 36 provide a pick-up voltage, which may be greatly amplified as it is used as a control voltage and not as the drive current to rotate the balance wheel. The coil is in the form of a complete toroidal circle (a ring) and may be formed by winding fine wire on a form or by printing copper or silver or by other depositing techniques for conductive metals.

As seen in FIG. 6, a voltage is produced by the pick-up at all times that the balance wheel is in motion. When the balance wheel stops, the voltage is at zero, at points b. In one direction, for example, clockwise, a positive voltage is produced (forward E.M.F.) and a negative voltage is produced (backward E.M.F.) in the opposite (counterclockwise) direction.

Preferably the impulse to the motor means is at the null (zero voltage) at the end of the swing of the balance wheel in one direction. For example, the motor means turns the pinning arm in the clockwise direction by 6 at the moment that the balance wheel has stopped in its clockwise swing, for example at 150 past the rest position 104 of the balance wheel. The turning of the pinning arm winds up the hairspring 6 more, in the same direction of winding, than the hairspring is wound by the spring of the balance wheel.

The pick-up provides a rising and falling voltage, that is, positive and negative, which is more or less regular in shape, depending upon the regulartory of the amplitude of the balance Wheel. A typical voltage output curve, which is charted against time, is shown in FIG. 6. A complete cycle is a positive for a half-cycle and a negative for a half-cycle, the full cycle being shown as from S to F. It is desired that the motor means be activated only when the balance wheel comes to its momentary rest position at the end of its swing at one of the ends of the swing. For this purpose it can be assumed that the polarity of the magnet is such that the desired end of the swing at which the pulse is to be given in a negative-topositive going voltage direction. In FIG. 6 it is desired that the pulse occur when the voltage moves in the direction from a to b to c and that it does not occur when the voltage moves in the direction from d to e to f. The voltage output pulse to the motor should occur at the transition point, that is, at the zero voltage of the pick-up, which would be at the point b.

The sequence of voltages from negative to positive is taken advantage of in constructing a suitable control circuit. The block diagram of such a circuit is shown in FIG. 7 and a detailed wiring diagram is shown in FIG. 8. It is seen from FIG. 6 that when the voltage moves from a to b to c it moves from a negative to a positive voltage. The pick-up 50 of FIG. 7 provides, at its output terminal 51, both a negative and a positive voltage. This voltage is split by wiring a positive leg 52 in parallel with a negative leg 53. The positive leg is simply a conducting wire. The negative leg 53 is connected in series with an inverter circuit 54. The inverter circuit 54'changes the negative pulses to positive pulses. The inverter circuit 54 is not sensitive (does not respond) to positive pulses. The output of the inverter circuit 54 is connected in series with a time-delay circuit 55. The time-delay circuit 55 has the effect of slightly delaying the positive pulse from the inverter circuit 54. Both the positive leg 52 and the output of the time-delay circuit 55 are connected to a digital and circuit 56. The and circuit 56 provides an output only if there is a simultaneous input at its two input gates 57 and 58. The positive pulse to input gate 57 is derived from the positive leg 52. The positive pulse to the input gate 58 is derived from the time-delay circuit.

When the voltage moves from points a to b, it will provide a pulse (voltage input) to which the inverter 54 is sensitive. The inverter 54 will convert this input to a positive pulse. The time-delay circuit 55 will delay the transmission of that positive pulse. When the voltage continues to rise and moves from points b to c, it provides a positive pulse which is conducted by positive leg 52 to the input gate 57 of the and circuit 56. The and circuit 56 therefore sees a positive input which is simultaneous at its inputs 57 and 58. The input at its gate 57 is from the positive voltage b to c. The input at its gate 58 is from the negative voltage a to b which has been delayed so as to be simultaneous in time with the positive voltage bc by means of the time-delay circuit 55.

The and circuit 56, due to the simultaneous input at its gates 57 and 58, provides an output voltage at its output gate 59 This output voltage is conducted in series to the single-shot multivibrator 60. The single-shot multivibrator 60 provides an output pulse at its output terminal 61 which is connected to the motor means 18. The motor means 18, for example a solenoid, provides a physical impulse to the index wheel. The duration of the pulse to the motor means 18 from the single-shot multivibrator 60 is independent of the duration of the input to the single-shot multivibrator 60 from the and circuit 56. The simultaneous overlap of the negative voltage a-b and the positive voltage b-c may be very short, in the order of microseconds. However, the output pulse to the motor means 18 can be of any desired duration, depending upon the values of the components used in the single-shot multivibrator 60. In the alternative to the single-shot multivibrator, other pulse means may be used whose output pulse is independent of the duration of its input trigger voltage, for example, a Schmitt trigger or a strongly damped oscillator might be employed in place of singleshot multivibrator 60.

A suitable circuit is shown in the wiring diagram of FIG. 8. However, it should be understood that this is merely one embodiment of the various circuit components as shown in FIG. 7 and well-known circuits may be used for each of the components. Preferably the entire circuit is formed by micro-circuit techniques, for example, on a single wafer of silicon. The circuit, although it may appear complex, may be made very small using micro-circuit techniques, as only the last stage handles appreciable amounts of current. The pick-up 50 terminates in the input side 70 of a pulse transformer 71. The output side of the pulse transformer 71 consists of two winding legs 72 and 73. The output winding 72 is connected to the wire 73 which is the positive leg 52 shown in FIG. 7. The other output winding of the pulse transformer 71 has one of its ends connected to the base of PNP transistor 75. The PNP transistor and its associated bias means is the inverter 54 which changes the negative voltage pulse at the winding 73 to a positive pulse. The bias means includes two current sources 76 and 77. The output of the transistor 75, which is its collector 78, leads to the timedelay circuit 79. The time-delay circuit includes a capacitor 80 and a leakage resistor 81. The size of the capacitor 80 depends upon the amount of delay desired or necessary to trigger the and" circuit 56. The output from the time-delay circuit 55 connects with one input gate 82 of the and circuit 56. The other input gate 83 of the and circuit is directly connected to the wire 74. The input gates 82 and 83 each consist of NPN transistors, respectively, transistors 84 and 85. The output of the transistor 84 is connected to the base 86 of NPN transistor 87. The emitter of transistor 87 is connected to the collector of the NPN transistor 88. The transistors 87 and 88 are connected in parallel to provide the and function of the circuit 56. The output of the and circuit 56, which is the wire 89, is taken from the collector of the transistor 87. There is a voltage output at wire 89 only if there is a simultaneous positive voltage at gages 82 and 83 of the and circuit 56. In the illustrated circuit, the switching means for the input gates are transistors 84 and 85, although other switching means may be used such as sensitive read relays or types of semi-conductor devices. The output of the and circuit 56 is lead to the capacitor 90, which is the input of the multivibrator 60. The multivibrator 60 includes a first NPN transistor 91 and a second NPN transistor 92. The circuit also includes a capacitor 93 and an inductance 94, as well as biasing and stabilizing resistors. The output of the multi vibrator circuit 60 is taken from the collector of transistor 92. The output wire 95 is connected to the coil of the motor means 18, which may be, for example, the coil of a solenoid.

Other types of pick-ups and other circuits may also be employed in the present invention. The pick-up shown in FIG. 9 consists of a single small magnet mounted at one end of balance wheel 101. A counter-weight (not shown) is fixed to the opposite end of the balance wheel. A small coil 102, of a few turns, for example, fifty turns, of fine wire is fixed on the frame member 103. Alternatively, the coil could be fixed to the pinning arm or the magnet fixed and the coil attached to the balance wheel. The coil is preferably positioned about 20-30 degrees, in the clockwise position, from the rest (center) position 104 of the balance wheel. This position enables even small swings of the balance wheel, for example, a total swing of 4060, to produce a voltage in the pick-up coil 102.

A suitable circuit for use with the pick-up arrangement of FIG. 9 is shown in FIG. 10. The circuit of FIG. 10 provides that a small voltage to its coil 102 suffices to produce a large current to motor means coil 18'. The circuit uses a complementary pair of transistors consisting of PNP transistor 105, NPN transistor 106, and also includes resistor 107, current source 108 and capacitor 109.

The watch of the present invention provides certain advantages compared to other electric or electronic balance wheel watches. The physical impulse is provided to the hairspring so that it is not necessary to have rollers on the balance wheel staff for contacts, power take-off pins, etc. This enables the watch to be thin. The balance wheel, in the present invention, may have a high amplitude, in excess of two turns, without problems due to overbanking. The clashing of the hairspring, at high amplitude, may be avoided by using an overcoil or helical type of hairspring. In addition, the watch of the present invention is free of moving electrical contacts and does not have mechanical interference with the balance wheel.

I claim:

1. A watch movement including a frame plate and a bridge member consisting of a frame assembly, time indicating means and power transferring means to operate said time indicating means;

a balance wheel fixed to a balance wheel staff, said staff and balance wheel constituting a balance wheel assembly;

bearing means associated with said frame plate and said bridge member to rotatably support said balance wheel staff;

a pinning arm having at its outer end an attachment means;

a hairspring connected at its inner end to said balance wheel assembly and connected at its outer end to said attachment means;

said pinning arm being movably connected to said frame assembly so that movement of said arm in one direction increases the winding of said hairspring;

motor means operable by electric current and attached to said frame assembly;

indexing means movable by said motor means, said indexing means providing power from said motor means to said power transferring means and also moving said pinning arm;

a set of contacts adapted to be connected to a source of electric current;

an electronic circuit operable to provide current from said source to said motor means; and

pick-off means associated with said balance wheel assembly to provide a timing control for said circuit.

2. A watch as in claim 1 wherein the said pinning arm is connected to a bushing rotatably mounted in said frame assembly and said bushing is rotated through a complete rotation by said indexing means.

3. A watch as in claim 2 wherein said indexing means 7 is a geared wheel and said bushing is directly fixed on said index wheel.

4. A watch as in claim 1 wherein said pick-off means includes an electromagnetic system including a magnet which moves relative to a coil, the coil providing a pickoff control voltage.

5. A watch as in claim 4 wherein the magnet is attached to the balance wheel and the coil is attached to the frame assembly and wherein said coil consists of a complete ring of conductors.

6. A watch as in claim 1 wherein said circuit has discrimination means to provide current to said motor means only at the end of the swing of the balance wheel in one direction.

7. A watch as in claim 1 wherein said motor means is a solenoid having a coil and a reciprocating armature, said armature carrying an indexing means at its outer end.

8. A watch as in claim 1 wherein said time indicating means are rotatable hands and said power transferring means is a train of meshing gears and pinions.

9. A watch as in claim 1 wherein said indexing means is an index wheel connected to said bushing.

10. A watch as in claim 1 wherein said index wheel is attached to the first wheel of a gear train, said gear train being the said power transferring means.

11. A watch as in claim 1 wherein a dry cell battery is positioned between said contacts as the power source.

12. A watch movement including a frame plate and a bridge member consisting of a frame assembly, a plurality of hands to indicate time and a gear train to rotate the said hands;

a balance wheel fixed to a balance wheel staff, said staff and balance wheel constituting a balance wheel assembly;

a pinning arm having at its outer end a hairspring attachment means, said pinning arm being connected at its inner end to a bushing rotatably mounted in said bridge member;

bearing means in said frame plate and within said bushing to rotatably support said balance wheel staff;

a hairspring connected at its inner end to said balance wheel assembly and connected at its outer end to said pinning arm attachment means;

motor means operable by electric current and attached to said frame assembly;

an index wheel indexed "by said motor means, said index wheel being connected to said bushing and rotating said gear train;

a source of electric current;

an electronic circuit operable to provide current from said source to said motor means; and

pick-off means associated with said balance wheel assembly to provide a timing control for said circuit.

References Cited UNITED STATES PATENTS 2,642,714 6/1953 Constant et al. 5828 FOREIGN PATENTS 1,3 04,243 8/ 1962 France.

RICHARD B. WILKINSON, Primary Examiner EDITH C. SIMMONS, Assistant Examiner US. Cl. X.R.

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