Horology: time measuring systems or devices – Winding means – With overwind prevention
Reexamination Certificate
2001-01-31
2002-08-27
Roskoski, Bernard (Department: 2841)
Horology: time measuring systems or devices
Winding means
With overwind prevention
C360S112000
Reexamination Certificate
active
06439762
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mainspring device, a timepiece, and a method of controlling the mainspring device and the timepiece. The present invention can be applied to a mechanical timepiece including a mainspring, which is wound up either by hand or automatically, and a timed annular balance, and to an electronic control type mechanical timepiece in which hands, affixed to a wheel train, are moved precisely by converting mechanical energy, output when the mainspring is unwound, into electrical energy by a generator in order to actuate a rotation controller using the electrical energy and control the rotation period of the generator.
2. Description of the Related Art
A mechanical timepiece whose hands are moved by utilizing mechanical energy of a mainspring is conventionally known.
Many electronic control type mechanical timepieces, such as that disclosed in Japanese Unexamined Patent Publication No. 8-5758, have been used in recent years. The timepiece, disclosed in the aforementioned document, indicates the exact time by precisely moving the hands affixed to a wheel train. The hands are moved by converting mechanical energy, output when the mainspring is unwound, into electrical energy by a generator in order to actuate a rotation controller using the electrical energy and to control the value of the current flowing in the coil of the generator.
As shown in
FIG. 22
, at the stage of winding up a mainspring when the number of windings reaches a predetermined number A, the torque that has been accumulating in the mainspring suddenly becomes large so that a very large torque is output when unwinding of the mainspring is started. The large torque is exerted onto a controlling portion of a speed regulator or an escapement, for example, which controls the rotational speed of a wheel train which rotates the mainspring. This sudden, large torque may cause component parts of the timepiece to break.
On the other hand, at the last stage of unwinding a mainspring when the number of windings is equal to or less than a predetermined number B, the torque output from the mainspring becomes very small, causing the hands to gradually slow down. This may cause the timepiece to indicate the wrong time. In an electronic control type mechanical timepiece, for example, when the mainspring is unwound to a certain degree, the amount of electrical power generated by the generator becomes so small that the generator rotates at a speed which is less than a speed that can be controlled. Therefore, the hands do not move precisely, causing the timepiece to indicate the wrong time.
To prevent this circumstance, clocks are provided with a winding-up and unwinding stop mechanism that prevents winding or unwinding of the mainspring beyond a certain maximum number of windings (during winding) or minimum number of windings (during unwinding). In general, the winding-up and unwinding stop mechanism uses a maltese-cross type mechanism, such as that shown in FIG.
23
. It includes a finger
102
, affixed to a barrel arbor
101
, and a gear
103
, called a maltese-cross, mounted to a barrel drum.
As shown in FIG.
23
(A), a finger head
102
a
of the finger
102
engages a cut in the gear
103
, which can rotate freely, initially, and move along the circumference of the finger
102
by progressively sliding therealong.
When the timepiece is wound, the barrel arbor
101
rotates, causing the finger
102
to rotate, so that one tooth of the gear
103
advances upon one rotation. Eventually, as shown in
FIG. 23
(A), a flat tooth
103
a
of the gear
103
engages the finger head
102
a,
thereby stopping the rotation of the barrel arbor
101
and locking the winding-up operation to prevent further winding of the mainspring.
During operation of the timepiece (that is, when the mainspring is being unwound), the finger
102
is fixed, and the gear
103
rotates along with the barrel drum, with the barrel arbor
101
at the center, such that one tooth advances upon one rotation, as shown in FIG.
23
(B). After the barrel drum rotates four times, the flat tooth
103
a
and the finger head
102
a
engage each other, as shown in FIG.
23
(C), thereby locking the unwinding operation to prevent any further unwinding of the mainspring.
The maltese-cross type winding-up and unwinding stop mechanism has a simple structure and requires few parts. However, since the winding operation is stopped by bringing a flat tooth of a gear into contact with a finger head, both components must be strong, which is realized by making them relatively large.
In addition, the finger and the gear must be placed upon a barrel drum. This causes the barrel drum to become thicker, so that the above-described maltese-cross winding-up and unwinding stop mechanism can only be used in a clock which has a large space for accommodating component parts in its interior, and cannot be used in watches which only have a small space available for components.
Therefore, in watches, it is difficult to limit the winding up and unwinding of the mainspring. As a result, breakage of parts still occurs when a very large torque is exerted onto the parts, and the wrong time is indicated when the torque becomes very small. Consequently, there is a demand for a way to output a torque whose value lies within a set range during winding and unwinding.
Accordingly, it is an object of the present invention to provide a mainspring device, a timepiece, and a method of controlling the mainspring device and the timepiece, wherein even when the mainspring device is used in a watch having a small space for accommodating component parts in its interior, neither an excessive torque nor an inadequate torque is output, that is, a torque that is within a set range is output at all times.
Electronic control type mechanical timepieces can control with high precision the rotation period of a generator, that is, the rotational period of the hands. This precision control results from driving a rotation control circuit, which includes a crystal oscillator, using electrical energy that has been generated in the timepiece. Such timepieces can indicate time more accurately than a conventional mechanical timepiece.
However, since it is necessary to stop the hands during hand adjustments, the wheel train, as well as the generator, must be stopped. Therefore, when the generator is stopped so that generation of electrical power is stopped, driving of the rotation control circuit can be continued only for a certain period of time using the electrical power stored in a charged capacitor. However, when the capacitor has completely discharged, the rotation control circuit stops.
After the rotation control circuit has stopped, when hand adjustments are completed and driving of the generator is started, hand movements cannot be controlled until driving of the control circuit is started. Therefore, there has been an attempt to preset the time during which hand movements cannot be controlled in order to correct the starting time of the control operation. Here, when the magnitude of the torque output from the mainspring changes, the amount of time until which the generator drives the control circuit also changes, so that the amount of correction is set in accordance with the magnitude of a predetermined output torque.
However, at the last stage of mainspring winding-up operations the torque accumulated in the mainspring suddenly becomes large, and a slight change in the winding amount greatly changes the magnitude of the torque, causing the torque to change greatly with every winding operation. Therefore, the corrections, even when they are made, are not sufficient.
It is another object of the present invention to provide a mainspring device, a timepiece, and a method of controlling the mainspring device and the timepiece, wherein when, for example, an electronic control type mechanical timepiece is used, corrections can be made very precisely even when the rotation control circuit has been stopped.
SUMMARY OF THE INVENTION
According to the present
Hara Tatsuo
Momose Yoshihiko
Gabrik Michael
Haro Rosalio
Roskoski Bernard
Watson Mark
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