This application claims priority from European Patent application No. 13163484.2 filed Apr. 12, 2013, the entire disclosure of which is hereby incorporated herein by reference.
The invention relates to an escapement system for a sprung balance resonator and, more specifically, for a high amplitude resonator of this type.
The purpose of a timepiece escapement system is to maintain and to count the oscillations of the balance wheel of a sprung balance resonator. To achieve this, the system receives the energy provided by a barrel and at the end of the chain by a seconds wheel in order to periodically allow a fragment of this drive energy to escape in order to give to the resonator energy lost through passive resistance (for example friction), the resonator including an inertia fly-wheel called a balance on the staff of which there is fixed a spiral spring called a balance spring.
The mechanical energy Em of this type of sprung balance resonator is given by the following relation:
where:
J is the inertia of the balance;
f is the frequency of the balance;
A is the oscillation amplitude of the balance.
Watchmaking technology tends to increase the energy of the sprung balance resonator in order to improve its precision and shock resistance, owing to the increase in the inertia J of the balance and/or the increase in the oscillation frequency f of the balance. However the increase in these parameters causes great difficulties.
Indeed, the increase in the inertia J of the balance tends to increase its weight which causes unwanted dry friction and/or lowers its aerodynamics. Further, the increase in oscillation frequency f requires a considerable increase in virtual power which is liable to decrease the power reserve of the timepiece. It is also clear that the increase in oscillation frequency f necessarily means that the escapement functions become shorter and shorter which represents a real kinematic and tribological challenge.
It is an object of the present invention to overcome all of part of the aforecited drawbacks by proposing an alternative escapement system for a sprung balance resonator which allows the mechanical energy Em of said resonator to be increased, while avoiding the aforementioned pitfalls.
Therefore, according a first variant, the invention relates to a timepiece including a resonator, formed by a balance associated with a balance spring and cooperating with an escapement system, characterized in that the escapement system includes a moving escape wheel arranged coaxially to the balance and driven by the gear train of the timepiece, a first fixed wheel having a first toothing and a second fixed wheel having a second toothing, the first fixed wheel being arranged inside the second fixed wheel in the same plane and leaving a space forming a closed channel, said first and second fixed wheels being arranged coaxially to the moving escape wheel, and a device for securing the outer end of the balance spring including a part hinged relative to the moving escape wheel and arranged to ensure, according to the state of winding of the balance spring, a radial movement of said outer end between said first and second toothings to maintain the resonator and to transmit its motion to the timepiece gear train.
According to a second variant, the invention relates to a timepiece including a resonator formed by a balance associated with a balance spring and cooperating with an escapement system, characterized in that the escapement system includes a moving escape wheel arranged coaxially to the balance and driven by the timepiece gear train, a first fixed wheel having a first toothing and a second fixed wheel which, mounted above the first wheel, has a second toothing, the first toothing having a smaller inner diameter than that of the second toothing, said first and second fixed wheels being arranged coaxially to the moving escape wheel and a device for securing the outer end of the balance spring including a part hinged relative to the moving escape wheel and arranged to ensure, according to the state of winding of the balance spring, a radial movement of said outer end between said first and second toothings to maintain the resonator and to transmit its motion to the timepiece gear train.
According to a third variant, the invention relates to a timepiece including a resonator formed by a balance associated with a balance spring and cooperating with an escapement system, characterized in that the escapement system includes a moving escape wheel arranged coaxially to the balance and driven by the timepiece gear train, a first series of teeth and a second series of teeth, the series of teeth are distributed circularly and coaxially to the moving escape wheel, the first series of teeth being distributed circularly in the same plane on a smaller radius than that of the second series of teeth, and a device for securing the outer end of the balance spring including a part hinged relative to the moving escape wheel and arranged to ensure, according to the state of winding of the balance spring, a radial movement of said outer end between said first and second series of teeth to maintain the resonator and to transmit its motion to the timepiece gear train.
In these three variants, the part hinged relative to the moving escape wheel preferably includes at least one impulse pin for cooperating with the first and second toothings or series of teeth. However, more particularly in the second variant, the hinged part of the securing device includes a first arm at the end of which there is fixed a first impulse pin arranged to cooperate with the first toothing of the first fixed wheel, and a second arm at the end of which there is fixed a second impulse pin arranged to cooperate with the second toothing of the second fixed wheel, each arm being capable of being offset in height.
It is thus clear that instead of increasing the inertia J of the balance and/or oscillation frequency f, the escapement system proposes, advantageously according to the invention, to increase the oscillation amplitude A of the balance in order to increase the mechanical energy Em of the resonator. Advantageously according to the invention, from relation (1), it is also clear that increasing the oscillation amplitude A of the balance will have a greater effect since amplitude A is squared.
It will be noted here that, for resonators with a low quality factor, including sprung balance resonators whose Q factor is less than 1000, the disruption to operation caused by the escapement system increases with an increase in the ratio between the maintenance angle and oscillation amplitude. It is thus clear, advantageously according to the invention, that the increase in amplitude A of the balance considerably reduces said disruptions.
In known pallets or detent type escapement systems, this increase in amplitude is not structurally possible, since amplitude is generally limited to 320 degrees. Further, the escapement system acts on the impulse pin integrated in the balance each time that the balance passes through its position of equilibrium or dead-point.
Advantageously according to the invention, where the desired amplitude exceeds the known limit of 320 degrees to achieve at least one complete revolution of the balance and is able to extend over several complete revolutions (this increase not being intrinsically limited), the present invention makes it possible to maintain the balance spring directly and not the balance as in conventional escapements. Maintaining the balance spring directly means that the escapement system can be started by the motion of the balance spring, for example by the radial movement of its outer end.
In accordance with other common advantageous features of the invention:
Other features and advantages will appear clearly from the following description, given by way of non-limiting illustration, with reference to the annexed drawings, in which:
A first embodiment of the present invention is illustrated in
Balance spring 2 is only represented by a limited number of coils for the clarity of the drawing and to avoid concealing the elements underneath said spring. However, balance spring 2 may, of course, include a larger number of coils without departing from the scope of the invention. The inner end 50 of balance spring 2 is fixed to an arbour 43, for example by means of an integral collet (shown more clearly in
According to the invention, escapement system 18 includes a moving escape wheel 3 arranged coaxially to resonator 15. In the example illustrated in
Escapement system 18 further includes a first fixed wheel 5 having an outer toothing 6 and a second fixed wheel 7 having an inner toothing 8. In the example illustrated in
Advantageously according to the invention, moving escape wheel 3 is provided with a device 9 for securing the outer end 10 of balance spring 2 to wind said spring. Further, securing device 9 is arranged to ensure, according to the state of winding of balance spring 2, a radial movement of outer end 10, which is made to cooperate alternately with toothing 6 of one of first and second fixed wheels 5 and 7 and then toothing 8 of the other. It is to be understood that this radial movement allows escapement system 18 to ensure the maintenance of resonator 15 and the escapement of seconds wheel 4.
As shown more clearly in
Preferably, according to the first embodiment of the invention, securing device 9 includes a hinged bar 11 to ensure the radial movement of outer end 10 of balance spring 2. Bar 11 is mounted, on the one hand, on a pivoting balance spring stud 12 carried by moving escape wheel 3 and on the other hand, on outer end 10 of balance spring 2. In the example illustrated in
When impulse pin 14 moves in channel 56, to facilitate its release from one 6 and then the other 8 of teeth 6, 8 fitted to fixed wheels 5 and 7, impulse pin 14 may be given the form of a cylindrical pin with a circular or elliptical section.
The operation of escapement system 18 according to the invention will now be explained with reference to
a) In
b) In
c) In
d) In
e) In
In the first embodiment of
Consequently, advantageously according to the invention, in addition to increasing mechanical energy Em as a result of the increase in oscillation amplitude A of balance 1, escapement system 18 also corrects the effects of gravity. It is also clear that escapement system 18 offers guaranteed self-starting of a high frequency movement even with high rigidity, increases stability and the quality factor without maintenance shocks, eliminates the risk of knocking and overbanking which are intrinsic to architecture, improves the efficiency of the escapement functions since losses are due solely to friction in the pivots and one wheel set and reduces the number of components to be oiled by omitting the pallets.
Of course, the invention is not limited to the first embodiment but is capable of various variants and alterations while maintaining the effects and advantages cited above. In particular, a second embodiment of escapement system 21 according to the invention is illustrated in
A third embodiment of escapement system 22 according to the invention is illustrated in
In order to better explain this third embodiment,
Balance 1 is associated with balance spring 24 which includes more coils than balance spring 2 of the first embodiment and in which the end of the inner coil 50 is fixed to arbour 43 for example by means of a collet. The end of outer coil 10 is attached to impulse pin 14 fixed to the free end 13 of bar 11, said bar is hinged to balance spring stud 12 carried by moving escape wheel 3 as in the first embodiment. Moving escape wheel 3 is provided with a toothing 73 meshed with seconds wheel 4, also as in the first embodiment, and is associated with inner element 40 of a ball bearing 41 whose outer element 42 is integral with unit 51 fixed to a fixed point of the timepiece, such as for example its main plate.
A fourth embodiment of the invention is illustrated in
It is also observed in
Second impulse pin 79 of lever 75 then enters the space separating two second teeth 73 which releases moving escape wheel 3 which then moves through a first impulse-angle by driving seconds wheel 4 until second impulse pin 79 abuts against a second tooth 73 of second fixed wheel 71.
A second impulse-angle is covered, as balance spring 2 changes to expansion, when the second impulse pin 79 is released from second tooth 73, lever 75 then rotating in the clockwise direction. The first impulse pin 77 then drops into the space separating two first teeth 72 and moving escape wheel 3 moves through a second impulse-angle by driving seconds wheel 4 until first impulse pin 77 abuts against a first tooth 72 of first fixed wheel 70. It will be noted in this fourth embodiment that, since fixed wheels 70 and 71 are arranged one on top of the other, second impulse pin 79 must have a shorter length relative to the length of first impulse pin 77.
Of course, the present invention is not limited to the illustrated example but is capable of various variants and alterations that will appear to those skilled in the art. In particular, the four embodiments presented above are capable of being combined in order to adapt to implementation constraints while maintaining the aforecited effects and advantages common to the four embodiments. By way of non-limiting example, the first 70 and second 71 fixed wheels of the fourth embodiment could be made in a single piece as proposed in the third embodiment.
It is also possible for the part hinged relative to moving escape wheel 3, 19, 45, i.e. by lever 75 or bar 11, to be replaced by a part of different shape, such as a substantially semi-cylindrical shaped part.
In an embodiment including several impulse pins 14, 77, 79, such as the fourth embodiment, it is possible to envisage offsetting in height the arms 76, 78 of part 75 hinged relative to moving escape wheel 3, 19, 45.
Further, the first and second toothings 6, 8, 72, 73 should be understood as stop members or contact surfaces for stopping and locking said at least one impulse pin 14, 77, 79. In this regard, the first and second toothings 6, 8, 72, 73 may be formed by pins, i.e. rods extending substantially parallel relative to said at least one impulse pin 14, 77, 79 in order to enter into contact with said at least one impulse pin 14, 77, 79 in accordance with the operation explained above. It is thus clear that the first and/or second toothings 6, 8, 72, 73 may in some way resemble a skeleton, i.e. not be entirely solid.
Thus, a fifth embodiment of escapement system 122 according to the invention is illustrated in
In order to better explain this fifth embodiment,
Balance 101 is associated with balance spring 124 which includes more coils than balance spring 2 of the first embodiment and in which the end of the inner coil 150 is fixed to arbour 143 for example by means of a collet. The end of outer coil 110 is attached to impulse pin 114 fixed to the free end 113 of hinged part 111.
Part 111 is hinged to balance spring stud 112 carried by moving escape wheel 103 as in the other embodiments. Moving escape wheel 103 is provided with a toothing 173 meshed with seconds wheel 4, also as in the other embodiments, and is associated with inner element 140 of a ball bearing 141 whose outer element 142 is integral with unit 151 fixed to a fixed point of the timepiece, such as for example its main plate.
Thus as seen more clearly in
Finally, in order to improve the locking of the above embodiments, magnetic bonding may also be provided between said toothings and said at least one impulse pin. Consequently, by way of example, said at least one impulse pin 14, 77, 79 may be magnetised and toothings 6, 8, 72, 73 or teeth 106, 108 may be made of paramagnetic material having a magnetic permeability greater than 1.5 or conversely, said at least one impulse pin 14, 77, 79 may be magnetised and toothings 6, 8, 72, 73 or teeth 106108 may be made of paramagnetic material having a magnetic permeability greater than 1.5.
Of course, the embodiments and/or alternatives and/or variants cited above can be combined with each other depending on the required applications.
Number | Date | Country | Kind |
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13163484.2 | Apr 2013 | EP | regional |