Horology: time measuring systems or devices – Mechanical time base – Mainspring
Reexamination Certificate
2000-07-19
2002-04-09
Miska, Vit (Department: 2859)
Horology: time measuring systems or devices
Mechanical time base
Mainspring
C368S184000, C368S204000
Reexamination Certificate
active
06367966
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a mechanical timepiece which operates by using as a driving source mechanical energy generated when a mainspring is released. In addition, the present invention relates to an electronic controlling type mechanical timepiece in which a portion of the mechanical energy of the mainspring is converted into electrical energy, and a rotation controlling means is operated by the electrical energy in order to control a period of rotation.
BACKGROUND ART
An electronic controlling type mechanical timepiece shown in
FIG. 16
is known, in which a mainspring used as an energy source drives a wheel train, and electrical power is generated by a generator rotated as a result of receiving the rotational motion from the wheel train in order to drive an electronic circuit which controls the period of rotation of the generator, whereby the wheel train is braked to regulate the speed.
In the electronic controlling type mechanical timepiece, rotation of a movement barrel
1
in which a mainspring
1
a
is accommodated is transmitted to a second wheel
6
to which a minute hand (not shown) is mounted, after which the rotation is transmitted successively to a third wheel
7
, a fourth wheel
8
, a fifth wheel
11
, a sixth wheel
12
, and ultimately to a rotor
13
of the generator. A second pinion wheel
90
to which a second hand (not shown) is attached meshes only with the third wheel
7
, so that it is situated outside a torque transmission path extending from the movement barrel
1
to the rotor
13
. In order to reduce unsteady movement of the second hand caused by backlash between the third wheel
7
and the second pinion wheel
90
, a second regulating spring with a suitable structure is sometimes provided.
In such an electronic controlling type mechanical timepiece, the speed of the rotor
13
is stably regulated, and, when the wheels
6
,
7
,
8
,
11
, and
12
, and the second pinion wheel
90
are formed with ideal shapes, the second pinion wheel
90
, that is, the second hand moves exactly at a constant speed of 1 rpm.
However, there are variations in the shapes of the wheels
6
,
7
,
8
,
11
, and
12
and the second pinion wheel
90
, so that, when, in particular, the second pinion wheel
90
with a small pitch circle is decentered from its axis of rotation, the rotational speed of the second pinion wheel
90
will not be 1 rpm, causing the second hand to shift.
To overcome this problem, the pitch circle size of the second pinion wheel
90
may be made larger. However, in such a case, since the speed-increase ratio (which is, in general, 60) from the second wheel
6
to the fourth wheel
8
needs to be maintained, a teeth-shaped module of the second pinion wheel
90
is made large, making it necessary to either make the third wheel
7
larger or increase the speed-increase ratio between the second wheel
6
and the third wheel pinion. This reduces the meshing efficiency.
FIG. 15
illustrates a graph showing the measured shift angles of the hand of the conventional electronic controlling type mechanical timepiece. In the timepiece, since a large speed-increase ratio in which the second pinion wheel
90
rotates nine times during the time the third wheel
7
rotates once is set, the pitch circle of the second pinion wheel
90
becomes small, so that the decentering of the second pinion wheel
90
greatly affects the shift angle of the hand. It has been confirmed that, during the time the second pinion wheel
90
rotates nine times, the second hand is greatly shifted by an angle in the range of from −1.2° to +4° from its normal position in a circumferential direction thereof.
The electronic controlling type timepiece uses the mechanical energy of the mainspring as a driving source, so that the larger the width of the mainspring (that is, the width of the timepiece in the thickness direction thereof), the longer the timepiece will continue operating.
However, forming the mainspring with a large thickness increases the thickness of the timepiece, thereby preventing the formation of a thin timepiece.
This problem not only exists in electronic controlling type mechanical timepieces, but also in conventional mechanical timepieces in which a wheel train is driven by a mainspring.
OBJECT OF THE INVENTION
Accordingly, it is an object of the present invention to provide a timepiece which makes it possible to reduce the amount by which a second hand is shifted, and which can continue operating for a longer time without increasing the thickness of the entire timepiece.
DISCLOSURE OF THE INVENTION
A timepiece according to one aspect of the present invention includes a speed-regulating device for regulating a speed of rotation of a wheel train, in which a mainspring serving as an energy source drives the wheel train,
wherein, of wheels of the wheel train, a wheel to which a second hand is mounted is disposed so that torque of the mainspring is transmitted to the speed-regulating device, the wheel to which the second hand is mounted including a pinion and a gear provided on a same axis of rotation, and being disposed so as not to overlap the mainspring when viewed in a plane.
In this invention, the wheel to which the second hand is attached includes a pinion and a gear, so that, by engaging a wheel disposed towards the mainspring and the pinion, and engaging this gear with a next gear (disposed towards the speed-regulating device), the diametrical dimension from the center of rotation of the wheel to which the second hand is attached to a portion where it engages the next gear can be made large without changing the speed-increase ratio from the mainspring side. Therefore, even if the wheel to which the second hand is attached gets decentered, the effects of the decentering at the center-of-rotation side becomes small, so that the amount by which the second hand gets shifted is reduced.
In addition, since the wheel to which the second hand is attached is disposed so as not to overlap the mainspring, the width of the mainspring can be correspondingly increased, so that the torque of the mainspring becomes large even if the thickness of the entire timepiece is not increased, thereby increasing the length of time the timepiece continues operating.
Due to the above, the above-described object is achieved.
The speed-regulating device may be constructed so as to regulate the speed of rotation of the wheel train by controlling a period of rotation of the generator by an electronic circuit driven by electrical power generated by the generator to which a rotational force from the wheel train has been applied.
Although, as in a mechanical timepiece, the speed-regulating device may comprise an escapement, the speed of the wheel train can be more precisely regulated when the electronic controlling type structure of the present invention is used.
It is desirable that the wheel to which the second hand is mounted and a gear of a barrel drum which accommodates the mainspring overlap each other when viewed in a plane.
In this structure, since the outside diameter of the gear of the barrel drum can be made large, the speed-increase ratio between it and a wheel at the wheel train side which engages the gear becomes large. Thus, the winding down of the mainspring when the train wheel is rotating at a constant speed can be slowed down, thereby increasing the length of time the timepiece continues operating.
A timepiece according to another aspect of the present invention in which a mainspring serving as an energy source drives a wheel train, and in which a speed of rotation of the wheel train is regulated by controlling a period of rotation of a generator by an electronic circuit driven by electrical power generated by the generator which has received a rotational force from the wheel train,
wherein, of wheels of the wheel train, a wheel to which a second hand is mounted is disposed so that torque of the mainspring is transmitted to the generator, the wheel to which the second hand is mounted including a pinion and a gear provided on a same axis of rotation;
Miska Vit
Seiko Epson Corporation
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