Information
-
Patent Grant
-
6712500
-
Patent Number
6,712,500
-
Date Filed
Tuesday, October 8, 200221 years ago
-
Date Issued
Tuesday, March 30, 200420 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
-
International Classifications
-
Abstract
The invention concerns an escapement device comprising a power source capable of delivering a variable torque based on the angle of rotation of a pinion fixed to said power source, said variable torque having at least a stable position and an unstable position. The device further comprises locking means capable of locking power transmission to an oscillator in a stable point of equilibrium and unlocking means capable of unlocking power transmission to said oscillator between a stable point of equilibrium and an unstable point of equilibrium.
Description
BACKGROUND OF THE INVENTION
The present invention concerns an escapement device for a timepiece.
For a timepiece and particularly a mechanical timepiece, the escapement device constitutes a master part which, on one hand, has to deliver the power required to maintain the oscillatory motion of the mechanical oscillator, balance wheel, and hairspring, and on the other hand, must transmit the oscillation frequency of the oscillator to the gears driving the time display.
PRIOR ART
Thus, the prior art in devices of this type is considerable. The handbooks published under the titles “Echappements et moteurs pas à pas” (Escapements and step motors) and “Théorie d'horlogerie” (Watch-making theory), ISBN 2-940025-10-X, both by the Swiss Federation of Technical Colleges, describe numerous escapement devices, and in particular those called “anchor”, “detent”, and “Graham” escapements.
The major drawbacks of these known devices are:
a poor efficiency; the best efficiency that can be obtained with these known devices is of the order of 30 to 40%, which limits the running time of the watch,
a limited working frequency; the efficiency of the known escapements drops off considerably when the oscillator frequency is raised to a perceptible degree, and moreover, anchor escapements develop a wear problem of the escapement wheel when the frequency is high,
difficulties of manufacture; for efficiencies of the order of 30 to 40%, the anchor escapements require a number of highly precise trimming operations.
SUMMARY OF THE INVENTION
It is a goal of the present invention, therefore, to propose an escapement device for a timepiece that is improved over known devices, that is, their known drawbacks have been reduced at least in part.
It is another goal of the invention to propose an escapement device that is insensitive to external impacts, and will not exhibit galloping effects.
It is yet another goal of the invention to propose a timepiece equipped with such an escapement device.
These goals are attained by an escapement device for timepieces as described in claim 1, as well as by a timepiece as described in claim 19. Particular embodiments or variants are described in the dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages of the invention will become apparent in the following detailed description, to be read while referring to the attached drawing comprising the figures where:
FIG. 1
presents a functional diagram of a mechanical watch,
FIG. 2
presents a first embodiment of an escapement device according to the invention,
FIG. 3
presents particulars of a blocking device in the escapement device of the preceding figure,
FIG. 4
presents a graph of the mechanical torque transmitted,
FIG. 5
presents a first embodiment of means to produce a variable torque,
FIG. 6
presents a graph of the magnetic torque transmitted,
FIG. 7
presents intermediate transmission means,
FIG. 8
presents the means of release,
FIG. 9
presents the means of power transmission,
FIG. 10
presents a graph of the resulting torque,
FIG. 11
presents a second embodiment of the means to produce a variable torque,
FIG. 12
presents a second embodiment of an escapement device according to the invention,
FIG. 13
presents particulars of the blocking device in the escapement device of
FIG. 12
,
FIG. 14
presents the means of release in the escapement device of
FIG. 12
,
FIG. 15
presents the means of power transmission of the escapement device of
FIG. 12
,
FIG. 16
presents another graph of the mechanical torque transmitted, and
FIG. 17
presents another graph of the magnetic torque transmitted.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In certain figures among those mentioned above, and described in detail herein-below, certain superimposed parts are represented as if they were transparent, which was done for a better understanding of their interactions.
FIG. 1
presents a functional diagram of a mechanical watch in which the mechanical energy that comes from a winding device, which is manual or automatic, is stored in a mainspring
1
so as to be distributed via a set of gears
2
to an escapement device
3
and to a display
4
.
The escapement device
3
has the purpose, on one hand to deliver the power required to sustain the oscillations of oscillator
5
, which in a general manner comprises a helical spring and an inertial mass, and on the other hand, to transmit the frequency given off by this oscillator to gears
2
in order to synchronize the time display with this frequency.
A good escapement device should not only have a good transmission efficiency between the power source and the oscillator but should also preserve the isochronism of the oscillator. To this end the inertias associated with the escapement device should be minimized and the power transfer between the escapement device and the oscillator should occur within a very short time while the velocity of the oscillator is largest.
FIG. 2
shows a first embodiment of an escapement device
3
according to the invention, comprising: a transmission wheel
30
driven by the set of gears
2
seen above, blocking means
31
, means for the generation of a magnetic torque
32
, intermediate means of power transmission
33
, unblocking means
34
, and power transmission means
35
. These different means will be described in greater detail hereinbelow.
FIG. 3
shows the transmission wheel
30
as well as the blocking means
31
. The transmission wheel
30
is set in rotation by the mainspring
1
via the gears
2
, and is driven by a mechanical torque of essentially constant value. The shaft
300
holding the transmission wheel
30
transmits the forward movement to the display device
4
. The blocking means
31
consist here of a shaped part or cam
310
mounted on the same shaft
333
as a pinion
330
that is part of the intermediate means of transmission shown in greater detail in
FIG. 7
, as well as of bolts
311
fastened to the transmission wheel
30
so as to protrude perpendicularly to the plane of said transmission wheel. The bolts
311
are regularly distributed over a perimeter of said transmission wheel. In the example of an embodiment presented, the transmission wheel
30
has ten bolts
311
, but depending on the requirements it could have a different number of bolts.
The shape and dimensions of the cam
310
as well as the diameter of the bolts
311
and of the perimeter along which they are inserted, are determined in such a way that, when the cam
310
which rotates together with the pinion
330
that is driven by the transmission wheel
30
, is turned with one or the other of its long sides
312
to the transmission wheel
30
, the transmission of torque can occur directly from the wheel
30
to the pinion
330
. To the contrary, when one of the short sides
313
arrives in front of a bolt
311
, blocking of this short side
313
of cam
310
on the bolt
311
occurs and the transmitted torque is interrupted.
FIG. 4
shows the mechanical torque transmitted to the shaft
333
that holds the pinion
330
, plotted as a function of the angle of rotation of said pinion. At first the curve shows a torque of constant value until the cam
310
arrives in the blocking position marked A
l
in the figure, where the transmitted torque becomes zero. Means of unblocking which will be described below then allow the device to become unblocked so that once again the torque of constant value can be transmitted until the next blocking occurs, marked at A
2
, and so forth.
The blocking means
31
here described give rise to two blocking positions, A
1
and A
2
, per turn of the pinion
330
, but they could just as well be conceived so as to give rise to a different number of blocking positions.
FIG. 5
shows a preferential embodiment of means allowing a torque to be obtained that varies as a function of the angle of rotation of pinion
330
. In this embodiment these means
32
are of a magnetic type, comprising a stator
320
and a rotor
321
that is arranged inside of said stator. The stator
320
consists of a ring of soft ferromagnetic material having along its inner perimeter two cavities
322
that are diametrically opposite to each other. The rotor
321
consists of a permanent magnet of cylindrical shape having a diametrical magnetization represented by the arrow in the drawing. The rotor
321
is mounted on the same shaft
333
as the pinion
330
and the cam
310
that have been described previously.
When the rotor
321
is set in rotation, the cavities
322
give rise to a magnetic torque acting on said rotor that is an essentially sinusoidal function, as can be seen in FIG.
6
. When the rotor
321
is oriented so that its axis of magnetization is parallel to the axis C—C in
FIG. 5
or perpendicular to the axis B—B containing the two cavities
322
, then the rotor
321
is in a stable equilibrium position, in which a slight angular displacement will tend to return the rotor toward this stable position, but when the same rotor is oriented so that its axis of magnetization is parallel to the axis B—B, it is in an unstable equilibrium position, which means that a slight angular displacement will tend to remove the rotor even further from this unstable position. The stable angular positions are marked S in the curve of
FIG. 6
, they correspond to a zero crossing of the curve with a negative slope of the torque, while the unstable angular positions are marked
1
in the same curve, and correspond to a zero crossing of the curve with a positive slope of the torque.
It should be noted here that the frequency of the curve representing the torque is twice that of rotation of the magnet or of pinion
330
, which is so because of the stator/rotor configuration described. With another configuration one could have a multiple other than two between these two frequencies.
The intermediate means of transmission
33
presented in
FIG. 7
essentially comprise the pinion
330
already seen above, as well as a second transmission wheel
331
mounted on a shaft
339
. We recall that the shaft
333
holding the pinion
330
also holds the cam
310
as well as the rotor
321
. The intermediate means of transmission
33
allow the different torques coming into play in the device to be combined.
The release means
34
of
FIG. 8
are of known construction. The release pallet
340
is integral with the oscillator (that is not presented in the figure), and oscillates about the shaft
341
. During its oscillatory motion in the counterclockwise direction, the tooth of pallet
340
encounters a tooth of the escapement wheel
342
, and imparts to it an impulse of torque in the clockwise direction. As the escapement wheel
342
is mounted on the same shaft
339
as the second transmission wheel
331
seen above, this impulse of torque is therefore transmitted from this transmission wheel
331
to the pinion
330
. By appropriate fixation of the escapement wheel
342
on the transmission wheel
331
, viz., in such a way that the impulse of torque be transmitted just after blocking of the pinion
330
by the blocking device described previously, the impulse of torque in a counterclockwise direction that is transmitted to the pinion
330
will release the cam
310
from its blocking position on the bolt
311
, allowing the transmission wheel
30
to perform part of a revolution until the next blocking occurs. The time display
4
has thus advanced by a time segment corresponding to one movement of pallet
340
.
FIG. 9
shows means
35
of power transmission to the oscillator which are of classical design, consisting of a transmission wheel
350
fixed on the same shaft
339
as the wheel
331
and the escapement wheel
342
, and of a shaped part
351
that is mounted on the shaft
341
seen above and attached to the balance wheel of the hairspring (not shown). When the wheel
350
turns clockwise as indicated, and one of its teeth encounters the short side
352
of the shaped part
351
that is moving more slowly counterclockwise, the wheel
350
will furnish kinetic energy to the part
351
or to the hairspring, thus allowing the oscillatory motion of the oscillator to be sustained.
As indicated, the release means
34
and the means
35
of power transmission are of known design, and are here described as examples for a realization; other devices performing the same functions may thus be foreseen as a replacement.
The resulting torque on pinion
330
which consists of the essentially constant torque transmitted by the wheel
30
and shown in
FIG. 4
, and of the variable torque transmitted by the magnetic stator/rotor group and shown in
FIG. 6
, is shown in FIG.
10
.
In the example shown for this first embodiment of an escapement device, this torque comprises two stable positions per turn of the pinion
330
which are marked S
1
and S
2
in the figure, and correspond to the two blocking positions in FIG.
4
. These two stable positions S
1
and S
2
are defined as previously by a zero crossing of the curve of torque with negative slope. The torque also comprises two unstable positions per turn of the pinion
330
which are marked I
1
and I
2
and correspond to the two unblocking positions in FIG.
4
. These two unstable positions I
1
and I
2
are defined as previously by a zero crossing of the curve of torque with positive slope.
One notices that the resulting torque is always positive, except in the blocking positions where it is negative.
In
FIG. 11
a second way is shown of how to obtain a variable mechanical torque having two stable points and two unstable points per turn of the wheel. A cam
323
is fixed on the same shaft
333
as the pinion
330
seen above; this cam has two concave portions and two convex portions. A spring lever
324
pivoting around one of its ends rests via a small wheel
325
on the periphery of cam
323
. The resulting torque of this device is a variable function with two stable points while the small wheel
325
is aligned with the axis C—C, and two unstable points while it is aligned with the axis B—B.
It can thus be seen that several possibilities exist to obtain a variable mechanical torque having at least one stable point and one unstable point.
FIG. 10
shows the mechanical torque acting on the shaft
333
of pinion
330
in the absence of contact with the oscillator, plotted as a function of the angle of rotation of said pinion, now one can describe in parallel the functioning of the device as a function of time.
After a first rotation the device arrives in a blocking position as described with reference to
FIG. 3
, and corresponding to the point S
1
in FIG.
10
. The device remains in this position for a time T
1
.
When the pinion
330
receives the unblocking impulse, as described with reference to
FIG. 8
, it changes from position S
1
to position I
2
in
FIG. 10
, the transition being accomplished within a very short time called T
2
and being less than one thousandth of a second. This time must be as short as possible in order to cause minimum perturbation of the oscillator.
Starting with this position the resulting torque, which becomes positive, furnishes to the oscillator via the power transmission means described the energy that is required by the oscillator during a time T
3
which is of the order of a few thousandths of a second, lasting until the next blocking position S
2
is attained.
A mechanical oscillator generally has an oscillation frequency of a few hertz, typically 4 Hz. For this frequency the period T that corresponds to the sum T
1
+T
2
+T
3
is 250 ms. In view of the low values reported above for T
2
and T
3
, the value of T
1
will then be just a few milliseconds smaller than that of T. It follows that the device is in a blocking position during the largest part of time T.
While a timepiece equipped with an escapement device such as that described above would satisfy the requirements indicated, such an escapement device when built into a wristwatch could be subject to a galloping effect.
In fact, in a wrist watch not subject to perturbations from outside, the amplitude of balance wheel oscillation in the clockwise direction is of the order of +240° relative to the axis that passes through the centers of rotation, and of the order of −240° in the opposite direction. Under these conditions the escapement wheel
30
advances one step in the clockwise direction in each balance wheel oscillation.
During an impact having a component in the plane of rotation of the escapement device, additional energy is transmitted to the oscillator via the inertia of the balance wheel, the result being that the amplitude of oscillation of the balance wheel may increase to a value higher than 360°. Under these conditions the unblocking means
34
in an escapement device such as that presented in
FIG. 2
provide more than one impulse per oscillation period, which provokes a fast advance of the watch here called galloping.
FIG. 12
presents another embodiment of an escapement device
3
according to the invention with which the drawback mentioned above can be avoided. This embodiment of the escapement device comprises as previously a transmission wheel
30
driven by the set of gears
2
(cf. FIG.
1
), blocking means
31
, means for the generation of a magnetic torque
32
, intermediate transmission means
33
, unblocking means
34
, and power transmission means
35
, the description of these different means being given hereafter.
The blocking means
31
of the escapement device of
FIG. 12
can be seen in
FIG. 13
, they consist of a toothed wheel
354
that cooperates with the pinion
330
. Here the teethed wheel
354
has eight teeth of asymmetric shape, is mounted on the same axle
300
, and pivots together with the transmission wheel
30
seen above.
In the position called rest position shown in
FIG. 13
, the end of tooth
332
of the pinion
330
rests against the straight flank of an asymmetric tooth of the wheel
354
.
When a torque is applied to the axis
300
of wheel
354
in the direction of the arrow, it exerts a force going through the center of rotation of shaft
333
of the pinion
330
. For this reason no torque is transmitted to the pinion, and this set of wheel and pinion remains blocked, a situation which persists until unblocking occurs by the unblocking means described below.
The unblocking means
34
of this embodiment can be seen in FIG.
14
. The release pallet
344
is integrated into the oscillator (not shown in the figure) and oscillates about the shaft
341
. During its oscillatory motion, the tooth
3441
of pallet
344
encounters either the tooth
3451
or the tooth
3452
of an intermediate part
345
, depending on whether the pallet
344
turns counterclockwise or clockwise. The oscillatory motion of the intermediate part
345
about the axis
3450
is limited by bolts
347
and
348
. The unblocking impulse coming from the balance wheel is transmitted to the pallet
346
that is mounted on the same axle
333
and pivots together with the pinion
330
seen above, which currently is blocked. This transmission of impulse actually occurs via the teeth
3454
and
3455
of the intermediate part
345
to one of the teeth,
3461
or
3462
, of the pallet
346
, and acts so as to unlock the set of wheel
300
and pinion
330
of
FIG. 13
, so that pinion
330
now can freely rotate.
FIG. 15
shows another embodiment of the power transmission means
35
; these means function in a manner similar to those described with reference to FIG.
9
.
The means for generation of a magnetic torque
32
that varies in time are similar to those described with reference to FIG.
5
.
This embodiment of the escapement device according to
FIG. 12
has the advantage over the embodiment of
FIG. 2
that in the case of an impact, the amplitude of oscillation of the balance wheel can be limited by bolts
347
and
348
, which thus prevent a loss of synchronization between the movement of the balance wheel and the movement of the wheel
30
, and the gallop mentioned above.
FIG. 16
shows another graph of the torque transmitted by an escapement device. As before, this torque is superimposed on that produced by the magnet in order to obtain the one shown in FIG.
17
.
An escapement device intended to function according to these graphs comprises blocking means having two stable positions in each direction of the oscillatory motion, in other words, four stable positions per period, which is another way of avoiding the galloping mentioned above.
Other embodiments and variants than those described above can yet be envisaged, and more particularly, pinion
330
could be replaced by an anchor performing an oscillatory motion, the arms of the anchor fork bearing two opposing magnets.
Relative to the escapement devices of the prior art, an escapement device according to the invention and according to one or other of the embodiments described in addition offers several marked advantages:
since the diameters of the rotating parts of the device according to the invention are smaller than those of corresponding parts in known devices, the inertia of said rotating parts is distinctly lower;
the power required for unblocking is lower; moreover, this unblocking is generally not attended by a recoil motion as in known anchor escapements;
thanks to the torque varying according to a curve, which is sinusoidal in the embodiments described, a maximum of torque is available just behind the unblocking position, which implies that the maximum power is transmitted immediately after unblocking, that is, over a limited angle of oscillation of the oscillator, at the moment when this oscillator has its highest velocity; in this way the isochronism of the oscillator is maximally preserved;
the transmission wheels have classical profiles with transmission efficiencies of the order of 90%;
Since certain transmissions of motion occur via gear wheels, greasing is not required as often as with traditional transmissions.
An escapement device as described according to one or the other of its embodiments is readily built into a timepiece, and particularly into a wristwatch, when considering the small diameter of the components of said device.
Claims
- 1. An escapement device notably for a timepiece, comprising a mobile organ of power transmission toward an oscillator able to receive said power and of transmitting an oscillation frequency,a first means able to produce at least a first portion of the power intended to supply the oscillator, said first means having a configuration such that it will supply a mechanical torque that is essentially variable as a function of the angle of angular displacement of said mobile organ, said mechanical torque having at least one stable position and at least one unstable position during one period of angular displacement of said mobile organ.
- 2. A device according to claim 1, including second means able to produce a second portion of the power intended to supply the oscillator, said second means having a configuration such that it will supply a mechanical torque that is essentially constant as a function of the angle of angular displacement of said mobile organ.
- 3. A device according to claim 2, including blocking means able to block the power transmission of said second means which are able to produce a second portion of the power intended to supply the oscillator.
- 4. A device according to claim 3, wherein the power transmitted to the oscillator by said mobile organ derives from the combination of said first means of power generation and of said second means of power generation, said power transmission being blocked during operation of said blocking means.
- 5. A device according to claim 4, wherein the mobile organ of power transmission is a rotating pinion that always transmits a positive mechanical torque, except for moments in time where the torque is between a stable position and an unstable position.
- 6. A device according to claim 5, wherein the torque transmitted by said pinion has two stable positions and two unstable positions per turn of said pinion.
- 7. A device according to claim 5, wherein the torque transmitted by said pinion has four stable positions and four unstable positions per turn of said pinion.
- 8. A device according to claim 5, wherein said first means able to generate at least a first portion of the power intended to supply the oscillator comprises a rotor bearing a magnet which rotates together with said pinion, said rotor being placed into a magnetic circuit.
- 9. A device according to claim 8, wherein the magnetic circuit consists of a stator surrounding said rotor, said stator exhibiting at least one asymmetry.
- 10. A device according to claim 5, wherein said first means able to generate at least a first portion of the power intended to supply the oscillator comprises a cam exhibiting at least one concave portion and one convex portion and rotating together with said pinion, a lever resting against the periphery of the cam while being pressed against said periphery by an elastic means.
- 11. A device according to claim 3, wherein the blocking means has a configuration such that it operates in stable equilibrium points of a curve of transmitted torque.
- 12. A device according to claim 11, wherein the blocking means has a configuration such that its operating point in the stable equilibrium points of the curve of transmitted torque is closer to the unstable equilibrium position of the mechanical torque furnished by said first means which are able to generate said first portion of the power intended to supply the oscillator, than to the stable position of the mechanical torque transmitted by the same first means.
- 13. A device according to claim 12, wherein the mobile organ is a rotating pinion that always transmits a positive mechanical torque except for moments in time where the torque is between a stable position and an unstable position, the blocking means comprises a cam having at least one peripheral blocking portion, said cam being fixed to said pinion of power transmission for the supply of said oscillator, and a transmission wheel equipped with protruding projections cooperating with said cam in order to block said escapement.
- 14. A device according to claim 12, wherein the blocking means comprises said pinion of power transmission for the supply of said oscillator and a toothed wheel exhibiting a number of asymmetric teeth cooperating with said pinion in order to block said escapement.
- 15. A device according to claim 13, including an unblocking device able to command resumption of the transmission of power intended to supply the oscillator, said unblocking device having a configuration such that it operates between a stable equilibrium point and an unstable equilibrium point of the curve of transmitted torque.
- 16. A device according to claim 15, wherein the unblocking device comprises a release pallet mounted on said oscillator, said release pallet being able to transmit an impulse of torque to an escapement wheel able to retransmit this impulse to said pinion, said impulse being able to unblock said cam blocked by one of said protruding projections.
- 17. A device according to claim 15, wherein the blocking means comprises said pinion of power transmission for the supply of said oscillator and a toothed wheel exhibiting a number of asymmetric teeth cooperating with said pinion in order to block said escapement, the unblocking device comprising a release pallet mounted on said oscillator, said release pallet being able to transmit an impulse of torque to an intermediate part mounted so as to pivot oscillating about an axis, said intermediate part being able to retransmit this impulse to another pallet mounted on said pinion which is able to unblock said pinion that is blocked against a tooth of the toothed wheel.
- 18. A device according to claim 17, wherein the amplitude of oscillating pivoting of the intermediate part is limited by two bolts.
- 19. A timepiece equipped with an escapement device according to claim 1.
Priority Claims (2)
Number |
Date |
Country |
Kind |
727/2000 |
Apr 2000 |
CH |
|
1332/2000 |
Jul 2000 |
CH |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/CH01/00148 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO01/77759 |
10/18/2001 |
WO |
A |
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Number |
Name |
Date |
Kind |
3660737 |
Sakai et al. |
May 1972 |
A |
3892066 |
Watkins |
Jul 1975 |
A |
4007582 |
Dugan et al. |
Feb 1977 |
A |
Foreign Referenced Citations (2)
Number |
Date |
Country |
463 400 |
Jan 1963 |
CH |
1 522 609 |
Aug 1968 |
FR |