AUTOMATICALLY STARTING AND SECURED DETENT ESCAPEMENT FOR A TIMEPIECE

Abstract

A horological detent escapement for a horological movement arranged to transmit a torque from said horological movement to an oscillating regulating organ of said horological movement, the regulating organ comprising a first mobile body and the escapement comprising a second mobile body and an escapement wheel. Said escapement wheel being arranged so as to transmit, during a half-phase of each oscillation of the regulating organ, a torque to said regulating organ via a direct impulse. The second mobile body comprises an indirect impulse means arranged so as to be in contact with the escapement wheel during normal operation and be out of contact during the other half-phase of each oscillation of the regulating organ when the escapement wheel does not transmit torque to the regulating organ, so as to transmit torque to said regulating organ via an indirect impulse, following an inadvertent movement or inadvertent stoppage of the horological movement.

Claims

1. A horological detent escapement adapted to be integrated in a horological movement and arranged to transmit a torque originating from an energy source of said horological movement to an oscillating regulating organ of said horological movement, the regulating organ of the horological movement comprising a first mobile body, the escapement comprising: a second mobile body configured to cooperate with said first mobile body and configured to be stopped by the second mobile body in a first or a second position defined respectively by a first and a second banking against which said second mobile body comes to rest, the second mobile body comprising an indirect impulse transmitter; and an escapement wheel, said escapement wheel being arranged so as to transmit, during a half-phase of each oscillation of the regulating organ, a torque to said regulating organ via a direct impulse; wherein said second mobile body is arranged and positioned so as to be, during the whole oscillation of the regulating organ during the normal functioning of the escapement, out of contact with the escapement wheel, while being capable of coming into contact, during another half-phase of each oscillation of the regulating organ during which the escapement wheel does not transmit torque to the regulating organ by means of a direct impulse, with the escapement wheel, so as to transmit a torque to said regulating organ of the horological movement by means of an indirect impulse, via the second mobile body, following an inadvertent movement or an inadvertent stoppage of the horological movement.

2. The horological escapement according to claim 1, wherein said energy source comprises a barrel spring and said regulating organ comprises a balance.

3. The horological escapement according to claim 2, wherein said first mobile body of the regulating organ of the horological movement comprises a roller carried by an axis of the balance.

4. The horological escapement according to claim 3, wherein said second mobile body of the escapement comprises pallets, said roller being adapted to cooperate with said pallets.

5. The horological escapement according to claim 4, wherein said escapement wheel comprises a number of teeth situated in the range of 13 to 19.

6. The horological escapement according to claim 3, wherein the first mobile body comprising said roller comprises a circular plate surrounded by a skirt having internal and external walls, said skirt having a notch arranged so as to be traversed by a finger fixed on the second mobile body, the second mobile body being stopped in the first position when it is resting on the first banking and its finger adjoins the internal wall of the skirt and being stopped in the second position when it is resting on the second banking and its finger adjoins the external wall of said skirt.

7. The horological escapement according to claim 6, wherein said second mobile body comprises at least one securing and guiding surface oriented in a direction substantially opposed to said finger so as to secure said second mobile body during the functioning phase of the escapement during which the finger fixed on the second mobile body traverses the notch of said skirt of the first mobile body.

8. The device according to claim 7, wherein said securing and guiding surface is arranged and positioned so as to be, during the impulse phase of the balance by the escapement wheel, at an exterior periphery of the trajectory of the escapement wheel of said escapement, so as to be capable of coming into contact with said escapement wheel in order to secure the second mobile body, respectively the pallets, preventing it from returning, following an inadvertent movement, on the trajectory of the escapement wheel.

9. The horological escapement according to claim 1, wherein said second mobile of the escapement is given an angular movement or a rectilinear movement.

10. The horological escapement according to claim 9, wherein said second mobile body of the escapement comprises pallets, said roller being adapted to cooperate with said pallets.

11. The horological escapement according to claim 9, wherein the first mobile body comprising said roller comprises a circular plate surrounded by a skirt having internal and external walls, said skirt having a notch arranged so as to be traversed by a finger fixed on the second mobile body, the second mobile body being stopped in the first position when it is resting on the first banking and its finger adjoins the internal wall of the skirt and being stopped in the second position when it is resting on the second banking and its finger adjoins the external wall of said skirt.

12. The horological escapement according to claim 1, wherein said indirect impulse transmitter comprising an indirect impulse pallet-stone situated substantially close to the pivoting axis of said second mobile body, respectively said pallets, in particular by an indirect impulse pallet-stone situated on the first half, adjacent to said pivoting axis, of the arm of the pallets carrying the exit lock pallet-stone.

13. The horological escapement according to claim 12, wherein said indirect impulse pallet-stone is made from a low-friction and low-wear material.

14. The horological escapement according to claim 13, wherein said indirect impulse pallet-stone comprises ruby or sapphire.

15. The horological escapement according to claim 13, wherein said escapement wheel comprises a number of teeth situated in the range of 13 to 19.

16. The horological escapement according to claim 1, wherein the escapement is a direct impulse escapement comprising an escapement wheel transmitting the impulse directly to the balance.

17. The horological escapement according to claim 16, wherein the escapement is a Robin-type escapement.

18. A horological movement comprising an energy source, a regulating organ, an escapement and a train, wherein the escapement is a horological escapement according to claim 1.

19. A timepiece, comprising a horological escapement according to claim 1, the horological movement comprising the horological movement of claim 13.

20. A timepiece according to claim 14, wherein the timepiece is a chronograph watch or split-time counter watch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The attached drawings represent schematically and by way of example the prior art as well as an embodiment of the invention.

[0015] FIGS. 1A to 1F illustrate schematically various escapements according to the prior art; FIG. 1A represents by a perspective view a Swiss lever escapement, FIG. 1B shows by a top view a detent escapement, FIG. 1C shows by a top view a Robin escapement, FIG. 1D shows by a top view an escapement according to European patent EP 1 122 617, FIG. 1E shows by a top view the escapement designated as radial double impulse escapement and FIG. 1F shows by a top view the coaxial escapement.

[0016] The series of FIGS. 2A to 2J schematically illustrates by top views the principal phases of functioning of the escapement according to European patent EP 1 122 617, when the functioning of the escapement is taking place normally.

[0017] FIG. 3 shows by a schematic top view an escapement according to the present invention.

[0018] The series of FIGS. 4A to 4J schematically illustrates by top views the principal phases of functioning of the escapement according to the present invention, when the functioning is taking place normally.

[0019] FIG. 5 schematically illustrates by a top view a phase of functioning of the escapement according to the present invention when the functioning of the escapement is taking place abnormally, following an inadvertent movement or an inadvertent stoppage of the horological movement, the indirect impulse means in this case coming into contact with the escapement wheel and transmitting a torque to the regulating organ by means of an indirect impulse via the second mobile body.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The invention will now be described in detail with reference to the attached drawings illustrating by way of example an embodiment of the invention.

[0021] The present invention relates to an escapement intended to be integrated in a timepiece, preferably in a wristwatch. For reasons of simplification of the language used, reference will be made below indiscriminately to timepiece and watch, without, however, wishing to limit the scope of the corresponding explanations which extend to any type of timepieces. In particular, an escapement according to the present invention is a direct impulse escapement, in particular an escapement of the Robin type, and the invention is, in a particularly preferred manner, realized by an escapement as described in European patent EP 1 122 617, respectively in the patent application CH 712 288. Although the following description will only explain in detail the specific case of the integration of the invention in an escapement as described in European patent EP 1 122 617, a use of the invention in combination with other types of escapement is possible, and the following explanations extend by analogy to any type of detent escapement, i.e. to any type of direct impulse escapement as well as to various types of lever escapement.

[0022] In order to allow for a better understanding of the context of the present invention, the following description will briefly recall the structure and the functioning of an escapement according to European patent EP 1 122 617. Given that the lever escapements in general and the direct impulse escapement described in European patent EP 1 122 617 are known to the person skilled in the art, this part of the description will be limited, as far as possible, to the facts linked to the context of the present invention. Likewise, the nomenclature used in European patent EP 1 122 617 will also be used, as far as possible, in the present description.

[0023] FIG. 1D is a top view of an escapement according to European patent EP 1 122 617 which allows its structure to be easily understood. This escapement includes, in generic terms, a first mobile body 1 and a second mobile body 2. The first mobile body 1 turns about an axis 1.1 and is capable of stopping the second mobile body 2 in a first or a second position defined respectively by a firstand a second banking 4.1, 4.2 against which said second mobile body 2 comes to rest. The first mobile body 1 is realized by a roller, respectively by a circular plate 1.2 surrounded by a skirt 1.2.1 having internal 1.2.1.1 and external 1.2.1.2 walls, said skirt 1.2.1 having a notch 1.2.1.3 arranged such as to be traversed by a finger 2.2.3 fixed on the second mobile body 2. As described in further detail in European patent EP 1 122 617 to which reference is made with respect to this point, the second mobile body 2 can be given a rectilinear movement, such that its finger 2.2.3 always moves radially to the first rotating mobile body 1, this configuration not being illustrated in the figures, or can be given an angular movement, by being articulated about a pivoting centre 2.1, the pivoting centre 2.1 being selected such that its finger 2.2.3 also moves substantially radially to the first rotating mobile body 1 when it traverses the notch 1.2.1.3 of said skirt 1.2.1. These two variants being equivalent at the functional level for the present invention, it is only this latter configuration which will be described in detail below and which is illustrated in the figures. In all cases, the second mobile body 2 is stopped in the first position when it is resting on the first banking 4.1 and its finger 2.2.3 adjoins the internal wall 1.2.1.1 of the skirt 1.2.1 and it is stopped in the second position when it is resting on the second banking 4.2 and its finger 2.2.3 adjoins the external wall 1.2.1.2 of said skirt 1.2.1. For further details of structural nature of this device, reference is made to European patent EP 1 122 617.

[0024] The functioning of the escapement according to European patent EP 1 122 617 will be explained briefly below with reference to the series of FIGS. 2A to 2J which illustrates, schematically and at each position by top views, ten principal phases of functioning of an escapement of the Robin type equipped with the locking device according to European patent EP 1 122 617, each phase being illustrated at the start of the corresponding movement. In this case, the balance of the escapement acts as first rotating mobile body 1 and the pallets act as second mobile body 2. In FIGS. 2A to 2J, as in FIG. 1D, the balance 1 is not illustrated in its entirety, but is represented by the small circular roller 1.2 surrounded by the skirt 1.2.1 which is coaxially integral with the axis 1.1 of the balance 1, the latter also carrying the impulse roller which is not illustrated in the figures, which is also coaxially integral with the axis 1.1 and which is equipped with a direct impulse pallet-stone 1.3 as well as with a pin 1.4. Furthermore, the pallets 2 mounted in a pivoting manner about the pivoting centre 2.1 have a guard-pin 2.2 as described in European patent EP 1 122 617 carrying said finger 2.2.3 of the pallets 2, a fork 2.3 cooperating with said pin 1.4 as well as an entry lock pallet-stone 2.4 and an exit lock pallet-stone 2.5 cooperating in a manner well known to the person skilled in the art with the escapement wheel 3. The latter also cooperates with said direct impulse pallet-stone 1.3 in order to directly transmit an impulse to the balance 1. The nomenclature used above and the usual function of these parts in a lever escapement are known to the person skilled in the art.

[0025] FIG. 2A shows an escapement of the Robin type equipped with the locking device according to European patent EP 1 122 617, viewed from above, during the phase commonly designated entry unlocking, in which a tooth of the escapement wheel 3 rests on the entry lock pallet-stone 2.4 of the pallets 2, such that the escapement wheel 3 cannot rotate. The balance 1 is situated at the start of its half-oscillation in anti-clockwise direction, viewed from above according to FIG. 2A, the pin 1.4 on its impulse roller beginning to engage the fork 2.3 of the pallets 2 in order to push the latter, which were locked in the first position due to resting on the first banking 4.1 and its finger 2.2.3 adjoining the internal wall 1.2.1.1 of the skirt 1.2.1 of the safety roller of the balance 1, so as to unlock the entry lock pallet-stone 2.4 of the pallets 2 from the tooth of the escapement wheel 3 resting on it. This movement is made possible by the rotation of the balance 1 which brings the notch 1.2.1.3 arranged in said skirt 1.2.1 into a position allowing the finger 2.2.3 to traverse it, such that the finger 2.2.3 passes, during the subsequent steps, from the internal wall 1.2.1.1 to the external wall 1.2.1.2 of the skirt 1.2.1. The movements of the different parts are symbolised in the series of FIGS. 2A to 2J by corresponding arrows.

[0026] FIG. 2B shows the escapement, again viewed from above, during the phase designated impulse drop, in which the pin 1.4 on the impulse roller of the balance 1 has pushed the pallets 2 sufficiently far so that the tooth of the escapement wheel 3, having previously rested on the entry lock pallet-stone 2.4 of the pallets 2, is released, such that the escapement wheel 3 turns, under the effect of the driving force of the spring of the barrel transmitted by the gear train of the corresponding timepiece, in clockwise direction, still viewed from above.

[0027] FIG. 2C shows the escapement, viewed from above, during the phase designated impulse, in which the escapement 3 has rotated, under the effect of the driving force of the spring of the barrel, up to the point at which one of its teeth is touching the direct impulse pallet-stone 1.3 fixed on the impulse roller of the balance 1, such as to directly transmit an impulse to the balance 1 in order to maintain its oscillation. During this movement, the pin 1.4 on the impulse roller of the balance 1 continues to push the pallets 2 in clockwise direction.

[0028] FIG. 2D shows the escapement, viewed from above, during the phase designated entry drop, in which the pallets 2 have rotated sufficiently in clockwise direction so that the exit lock pallet-stone 2.5 of the pallets 2 has penetrated in the trajectory of the teeth of the escapement wheel 3. The latter thus continues its rotation until one of its teeth engages with said exit lock pallet-stone 2.5 of the pallets 2, the escapement wheel 3 being thus stopped again, while the balance 1 and the pallets 2 continue their half-oscillation in anti-clockwise direction, respectively pivoting in clockwise direction, viewed from above.

[0029] FIG. 2E shows the escapement, viewed from above, during the phase designated entry backlash, in which the escapement wheel 3 is effectively stopped, one of its teeth resting on the exit lock pallet-stone 2.5 of the pallets 2, while the balance 1 and the pallets 2 still continue their half-oscillation in anti-clockwise direction, respectively pivoting in clockwise direction, viewed from above.

[0030] FIG. 2F shows the escapement, viewed from above, during the phase designated exit lock, in which the escapement wheel 3 is still stopped by the exit lock pallet-stone 2.5 of the pallets 2, the latter now being stopped in the second position, as resting on the second banking 4.2 and its finger 2.2.3 adjacent to the external wall 1.2.1.2 of the skirt 1.2.1 of the safety roller of the balance 1. The balance 1, in turn, its situated at the dead point of its half-oscillation in anti-clockwise direction.

[0031] FIG. 2G shows the escapement, viewed from above, during the phase designated exit unlocking, in which, at the start of this functioning step, a tooth of the escapement wheel 3 rests on the exit lock pallet-stone 2.5 of the pallets 2, so that the escapement wheel 3 cannot yet rotate. The balance 1 is situated at the start of its half-oscillation in clockwise direction, viewed from above according to FIG. 2G, the pin 1.4 on its impulse roller beginning to engage the fork 2.3 of the pallets 2 in the other direction in order to push the latter, which were situatedas mentioned abovestopped in the second position as resting on the second baking 4.2 and its finger 2.2.3 adjacent to the external wall 1.2.1.2 of the skirt 1.2.1 of the safety roller of the balance 1, in anti-clockwise direction, viewed from above, such as to unlock the exit lock pallet-stone 2.5 of the pallets 2 from the tooth of the escapement wheel 3 resting on it. This movement is made possible by the rotation of the balance 1 which brings the notch 1.2.1.3 arranged in said skirt 1.2.1 in a position allowing the finger 2.2.3 to traverse it, such that the finger 2.2.3 passes back, during the following steps, from the external wall 1.2.1.2 to the internal wall 1.2.1.1 of the skirt 1.2.1.

[0032] FIG. 2H shows the escapement, viewed from above, during the phase designated exit drop, in which the pin 1.4 on the impulse roller of the balance 1 has pushed the pallets 2 sufficiently far so that the tooth of the escapement wheel 3, having previously rested on the exit lock pallet-stone 2.5 of the pallets 2 is released, such that the escapement wheel 3 rotates, under the effect of the driving force of the spring of the barrel transmitted by the gear train of the corresponding timepiece, in clockwise direction, viewed from above. During this movement, the balance 1 continues its half-oscillation in clockwise direction and the pin 1.4 on the impulse roller of the balance 1 continues to push the pallets 2 in anti-clockwise direction, such that the entry lock pallet-stone 2.4 of the pallets 2 penetrates again in the trajectory of the teeth of the escapement wheel 3. The latter thus continues its rotation until one of its teeth engages with said entry lock pallet-stone 2.4 of the pallets 2, the escapement wheel 3 being then stopped again. During this phase, the escapement wheel 3 does not transmit an impulse to the balance 1, because the direct impulse pallet-stone 1.3 is arranged and placed in such a manner on the impulse roller that it is not touched by the teeth of the escapement wheel 3 when the balance 1 carries out its half-oscillation in clockwise direction.

[0033] FIG. 2I shows the escapement, viewed from above, during the phase designated exit backlash, in which the escapement wheel 3 is effectively stopped, one of its teeth resting on the entry lock pallet-stone 2.4 of the pallets 2, while the balance 1 and the pallets 2 still continue their half-oscillation in clockwise direction, respectively the pivoting in anti-clockwise direction, viewed from above.

[0034] FIG. 2J shows the escapement, viewed from above, during the phase designated entry lock, in which the escapement wheel 3 is still stopped by the entry lock pallet-stone 2.4 of the pallets 2, the latter being again stopped in the first position as resting on the first banking 4.1 and its finger 2.2.3 adjacent to the internal wall 1.2.1.1 of the skirt 1.2.1 of the safety roller of the balance 1. The balance 1, in turn, is situated at the dead point of its half-oscillation in clockwise direction, ready to recommence an oscillation cycle again, such that the steps described above repeat themselves.

[0035] In this context, it is to be noted that the description figuring above of the functioning of the escapement according to European patent EP 1 122 617 is also valid for the escapement according to the patent application CH 712 288 and, in principle, applies by analogy to any escapement of the Robin type, respectively to any lever escapement, having a single beat, i.e. having a half-phase during each oscillation of the regulating organ during which there is no impulse.

[0036] FIG. 3 shows a schematic top view of an escapement according to the present invention. It can be seen therefrom that, in generic terms, such an escapement is adapted to be integrated in a horological movement and arranged to transmit a torque originating from an energy source of said horological movement to an oscillating regulating organ of said horological movement, the regulating organ of the horological movement comprising a first mobile body 1 and the escapement comprising a second mobile body 2 and also an escapement wheel 3. The first mobile body 1 cooperates with the second mobile body 2 by being adapted to stop the second mobile body 2 in a first or a second position defined respectively by a first and a second banking 4.1, 4.2 against which said second mobile body 2 comes to rest. The escapement wheel 3 is arranged such as to transmit, during a half-phase of each oscillation of the regulating organ, a torque to said regulating organ by means of a direct impulse. In addition, the said second mobile body 2 comprises an indirect impulse transmitter arranged and positioned such as to be, during the whole oscillation of the regulating organ during the normal functioning of the escapement, out of contact with the escapement wheel 3, whilst being capable of coming into contact, during the other half-phase of each oscillation of the regulating organ during which the escapement wheel 3 does not transmit torque to the regulating organ by means of a direct impulse, with the escapement wheel 3, in order to transmit a torque to said regulating organ of the horological movement by means of an indirect impulse, via the second mobile body 2, following an inadvertent movement or an inadvertent stoppage of the horological movement, in particular in order to ensure the self-starting of the horological movement.

[0037] In the majority of the practical realizations of a horological escapement, respectively of a horological movement, said energy source is formed by a barrel spring and said regulating organ is formed by a balance, said first mobile body 1 of the regulating organ of the horological movement being conventionally formed by a roller 1.2 carried by an axis 1.1 of the balance. Furthermore, and as referred to in greater detail in European patent EP 1 122 617, the second mobile body 2 of the escapement can, in principle, be given an angular movement or a rectilinear movement. In the first case, said second mobile body 2 of the escapement is, preferably, formed by pallets 2, said roller 1.2 carried by an axis 1.1. of the balance being adapted to cooperate with said pallets 2.

[0038] As regards more particularly the realization of said indirect impulse means or transmitter 2.6 of an escapement according to the present invention, it is preferably formed by an indirect impulse pallet-stone 2.6 situated substantially close to the pivoting axis of said second mobile body 2, respectively of said pallets 2. Preferably, said indirect impulse pallet-stone 2.6 is situated on the first half, close to said pivoting axis, of the arm of the pallets 2 carrying the exit lock pallet-stone 2.5, as illustrated in FIG. 3. This indirect impulse pallet-stone 2.6 can be produced in one piece with the pallets 2 or by a separate part mounted on the pallets 2. Preferably, the indirect impulse pallet-stone is realized by a separate part and made from a low-friction and low-wear material, such as ruby or sapphire.

[0039] As regards the realization of the escapement wheel 3 of an escapement according to the present invention, it comprises, in a preferred embodiment illustrated in FIG. 3, a number of teeth situated in the range of 13 to 19.

[0040] In addition, an escapement according to the present invention comprises, in a preferred embodiment, a locking device according to European patent EP 1 122 617, the structure and functioning of such a device having been described above and applying in an identical manner to an escapement according to the present invention comprising such a locking device. In a particularly preferred embodiment, an escapement according to the present invention also includes at least one securing and guiding surface as mentioned above and as described in detail in the patent application CH 712 288, this description of the structure and functioning of such a securing and guiding surface likewise applying in an identical manner to an escapement according to the present invention comprising such a securing and guiding surface.

[0041] As regards the functioning of an escapement according to the present invention, FIGS. 4A to 4J show by schematic top views the principal phases of functioning of the escapement according to the present invention, when the functioning is taking place normally, the invention being in these figures applied to the escapement according to European patent EP 1 122 617. In this context, it is to be noted that the description appearing above, with reference to FIGS. 2A to 2J, of the functioning of the escapement according to European patent EP 1 122 617 is wholly valid for this embodiment of an escapement according to the present invention. This point also applies to the embodiment of an escapement according to the present invention comprising at least one securing and guiding surface according to the patent application CH 712 288, respectively applies by analogy to all embodiments of an escapement according to the present invention, i.e. to any escapement of the Robin type, or even to any lever escapement, having a single beat, i.e. having a half-pass during each oscillation of the regulating organ during which there is no transfer of impulse, and being equipped with an indirect impulse means 2.6 according to the present invention. In fact, apart from the presence of said indirect impulse means 2.6 on the second mobile body 2 and a different number of teeth of the escapement wheel 3, the structure and the normal functioning of an escapement according to the present invention are identical to those of the escapement according to European patent EP 1 122 617, respectively to those of a corresponding escapement of the Robin type, given that the indirect impulse means 2.6 only takes an active role when an abnormal situation arises. Consequently, all the explanations appearing above in the context of the series of FIGS. 2A to 2J are valid for the normal functioning of an escapement according to the present invention as illustrated in the series of FIGS. 4A to 4J which show the same principal phases of normal functioning of an escapement according to the present invention as the series of FIGS. 2A to 2J. For reasons of simplicity, these explanations will not be repeated here, applying by analogy to the series of FIGS. 4A to 4J.

[0042] As regards the functioning of an escapement according to the present invention when an anomaly occurs, in particular following an inadvertent movement or an inadvertent stoppage of the horological movement, FIG. 5 illustrates by a schematic top view a phase of functioning of the escapement according to the present invention during which the indirect impulse means 2.6 takes an active role. In fact, when the functioning of the escapement takes place abnormally, following an inadvertent movement or an inadvertent stoppage of the horological movement, the indirect impulse means 2.6 comes in contact with one of the teeth of the escapement wheel 3 and transmits a torque to the regulating organ by means of an indirect impulse via the second mobile body 2. The indirect impulse pallet-stone 2.6 can also give an impulse to the balance when its amplitude reduces following the letting down of the barrel, which can be designated as an impulse at order, this case not being illustrated in the figures. The present invention thus allows to avoid the disadvantages of the escapements of the prior art, mentioned in the introduction, by proposing an escapement which, in addition to the components of the escapement according to European patent EP 1 122 617, respectively in general of a detent escapement, or of the Robin type, further comprises said indirect impulse means 2.6, preferably in the form of an indirect impulse pallet-stone mounted close to the pivoting axis of the pallets 2, this indirect impulse means 2.6 remaining out of contact with the escapement wheel 3 during the whole oscillation of the regulating organ during the normal functioning of the escapement and only intervening during an abnormal functioning to carry out a transfer of an indirect impulse.

[0043] In this context, it can be added that, about fifty years ago, by carrying out observations with a high speed camera, horologists were surprised to observe that during the functioning of the lever escapement, after its release by the balance, the escapement wheel travels a substantial path before one of its teeth catches up one of the pallet-stones of the pallets. In fact, almost one third of the length of the entry- and exit-pallets of conventional pallets is not used because the corresponding tooth of the escapement wheel has not yet succeeded in making contact. This is also the case for the direct impulse escapements, in which the teeth of the escapement wheel must catch up the impulse pallet-stone situated on the impulse roller of the balance so as to carry out a transfer of a direct impulse. In the two cases, this is generally considered as a fault and various means are used to minimize it. An escapement according to the present invention having an indirect impulse pallet-stone on the pallets which is not caught up at all by the teeth of the escapement wheel during the normal functioning of the escapement, i.e. which does not take part at all in the normal functioning of the escapement, but which only intervenes during an abnormal functioning, is therefore to a certain extent contrary to the traditional technical teaching in the field of horology. On the other hand, in the case of loss of amplitude, shock or the tendency to stoppage of the escapement, one of the teeth of the escapement wheel comes in contact with the indirect impulse pallet-stone and allows an indirect impulse to be carried out, which leads, if applicable, to the automatic re-starting, given that the presence of the indirect impulse pallet-stone 2.6 brings an additional geometric constraint which is exploited during a specific phase of the functioning of the escapement and the geometry of which can be adapted as a function of the needs according to the practical case of application, for example by variation of the placement and/or of the form of the indirect impulse pallet-stone. It can also be noted at this point that the statement above is underlined by the configuration of the radial double impulse escapement mentioned in the introduction, given that the third impulse pallet-stone L positioned centrally on the pallets of this escapement, as can be seen in FIG. 1E, transmits systematically a torque to the balance at each half-phase of the oscillation of the regulating organ during which the escapement wheel does not transmit a torque to the regulating organ by means of a direct impulse, i.e. this third impulse pallet-stone always participates in the normal functioning of the radial double impulse escapement. Consequently, the present invention can also be realized in an escapement of the radial double impulse type or in the coaxial escapement which are mentioned in the introduction by replacing the third impulse pallet-stone present in and participating always in the normal functioning of these escapements by an indirect impulse pallet-stone 2.6 according to the present invention, which only intervenes during an abnormal functioning of the escapement.

[0044] In view of the arrangement and the functioning of a horological escapement according to the present invention, as described above, the person skilled in the art will understand that the present invention can be realized in any type of direct impulse escapement, in particular in a Robin escapement and, particularly preferably, in an escapement according to European patent EP 1 122 617 and according to the patent application CH 712 288. Generally, the present invention can be realized in any type of lever escapement having a single beat, without it being necessary or possible to mention all the cases of figures and all the corresponding details here. In view of the technical teaching appearing above, the person skilled in the art will also understand that the present invention concerns not only such an escapement, but also a horological movement comprising an energy source, a regulating organ, a gear train as well as such a horological escapement. In addition, the present invention also concerns a timepiece, preferably a mechanical wristwatch, comprising such a horological escapement, respectively such a horological movement. Preferably, it concerns a wristwatch having a chronograph mechanism or split-time counter mechanism, in which the advantages of a direct impulse escapement can be exploited particularly advantageously.

[0045] A horological escapement according to the present invention therefore allows the problem concerning self-starting of the single-beat escapements to be prevented, given that its indirect impulse pallet-stone comes into contact, for example following an inadvertent movement or an inadvertent stoppage of the horological movement and during the half-phase of the oscillation of the balance during which the escapement wheel does not transmit torque to the balance by means of a direct impulse, with the escapement wheel and transmits by means of an indirect impulse via the pallets a torque to the balance which is sufficient for re-starting the horological movement. At the same time, the present invention allows, in the case of application to the escapement according to European patent EP 1 122 617 and to that according to the patent application CH 712 288, to secure in a complementary manner the second mobile body 2 during the phase of functioning of the device during which the finger 2.2.3 fixed on the second mobile body 2 traverses the notch 1.2.1.3 of said skirt 1.2.1 of the first mobile body 1, such that the notch 1.2.1.3 in the skirt 1.2.1 can be enlarged. Thus, the tolerances of the parts involved during the exit of the finger of the guard-pin outside the skirt can be relaxed, which allows constellations to be prevented in which a collision between said finger and said skirt of the locking device can occur. The indirect impulse means 2.6 therefore plays a role of self-starting means as well as, in a subsidiary manner, a role of securing means.

[0046] In summary, the present invention allows the realization of a horological escapement which has the above-mentioned advantages of a detent escapement and the self-starting of which in the case of inadvertent stoppage of the movement is ensured, such that it does not present the problem concerning self-starting of the single-beat escapements. In addition, the present invention allows the security of functioning of the escapement to be further improved, in particular in the case of the AP escapement, by allowing to relax the tolerances of the parts which are involved during the exit of the finger from the guard-pin outside the skirt and by thus preventing constellations in which a collision between said finger and said skirt of the locking device can occur. Furthermore, the proposed construction, consisting principally of the integration of an indirect impulse pallet-stone, is simple and robust and also reliable during the functioning of the escapement. Such an indirect impulse pallet-stone can be integrated in several types of detent escapement and/or lever escapement, such that the invention can be applied in a flexible manner to several types of timepieces. In particular, the invention can be applied, preferably, in mechanical wristwatches, notably in wristwatches equipped with a chronograph mechanism or split-time counter mechanism.