Detent escapement for timepiece

Abstract

The invention relates to a detent escapement intended to regulate the operation of a clockwork movement, this detent escapement (74) comprising an escape wheel (76) provided with a plurality of teeth (78) regularly spaced around a perimeter and a balance wheel (82), the balance wheel (82) being equipped with an impulse pallet (98) by means of which this balance wheel (82) receives driving impulses via the teeth (78) of the escape wheel (76), the balance wheel (82) being animated by an oscillating motion during which it performs, for each oscillation, an alternation during which it receives a driving impulse and an alternation without a driving impulse, the detent escapement (74) also comprising a hook (102) pivotally mounted on the balance wheel (82) and held in contact by an elastic member (106) against a stop (104),the detent escapement (74) being completed by a detent (108) which is capable of pivoting and which comprises a first arm (110) which collaborates with the escape wheel (76) to ensure that the latter is blocked just before the start of the driving impulse, as well as a second arm (112) which collaborates with the balance wheel (82) to allow the escape wheel (76) to disengage from its grip with the first arm (112) at the start of the driving impulse, and which limits the pivoting of this detent (108) to only a part of the oscillation of the balance wheel (82), the detent (108) also being arranged so as to block the escape wheel (76) again when the latter finishes giving the driving impulse to the impulse pallet (98) of the balance wheel (82).

Description

Technical field of the invention

[0001] The present invention relates to a detent escapement for a timepiece, in particular for a wristwatch. Technological background of the invention

[0002] An escapement is a mechanism that is placed between the escape wheel and the regulating organ of most timepieces. Produced by a barrel spring, the driving force is transmitted to the escape wheel, which in turn communicates this driving force to the escapement, whose function is to maintain the oscillations of a regulating organ called the balance.

[0003] The detent escapement first appeared during the 18th century, when maritime nations launched competitions to build the most accurate timekeeping instrument possible, allowing the most reliable determination of geographical position at sea. For this reason, detent escapements are still found mainly in marine chronometers today.

[0004] Detent escapements, expensive and delicate, are so-called lost-stroke escapements. In other words, detent escapements only give the balance one impulse with each oscillation, so that these oscillations always include an alternation without impulse, also called a "lost stroke."

[0005] A first embodiment of a detent escapement is illustrated in Figure 1attached to this patent application. Designated as a whole by the general numerical reference 1, this detent escapement comprises an escape wheel 2 whose teeth 4 rest on a stone 6. This stone 6 is carried by a body 8 of a detent 10 which equips a timepiece (not shown)

[0006] As can be seen in the drawing, the body 8 of the trigger 10 is terminated at a first end by a beak 12, and is connected at a second end to a frame 14 of the timepiece by a spring blade 16. Furthermore, the body 8 of the trigger 10 itself carries a trigger spring 18 bearing against the beak 12. This beak 12 against which the trigger spring 18 bears is located in the field of action of a release pallet 20 carried by a plate 22 of a balance 24.

[0007] When the balance wheel 24 and its plate 22 rotate counterclockwise, driving with them the release pallet 20, this release pallet 20 in turn drives the detent spring 18 and therefore the body 8 of the detent 10, which has the effect of releasing that of the teeth 4 of the escape wheel 2 which is engaged with the jewel 6 from its engagement with this jewel 6. Thus, with each alternation of the balance wheel 24 in the counterclockwise direction, the escape wheel 2 is released.

[0008] When tooth 4 of escape wheel 2 which rests on jewel 6 leaves the latter, another tooth 4 of escape wheel 2, acting on an impulse pallet 26 carried by plate 22 of balance 24, gives an impulse to balance 24.

[0009] Conversely, when the balance wheel 24 rotates clockwise, the impulse pallet 26 passes between the teeth 4 of the escape wheel 2, without effect on the latter, and drives the detent spring 18. The detent spring 18 leaves its support against the beak 12 of the body 8 of the detent 10, without driving the latter, and escapes the field of action of the impulse pallet 26. Finally, the detent spring 18 falls back to rest on the beak 12 of the body 8 of the detent 10, without performing any function. It is therefore understood that the alternation during which the balance wheel 24 rotates clockwise is the alternation also called "lost stroke" during which the escape wheel 2 does not give any impulse to the balance wheel 24.

[0010] A second embodiment of a detent escapement is illustrated in Figure 2attached to this patent application. This type of escapement is described in the work entitled “Echappements et moteurs pas-à-pas” by Messrs. Charles Huguenin, Samuel Guye and Maurice Gauchat, the second expanded edition of which was published by FET in 1974, page 169, Fig. 17-4.

[0011] On the Figure 2 , it can be seen that the detent escapement, designated as a whole by the general numerical reference 28, is composed of the following elements: escape wheel 30 provided with teeth 32; jewel 34; body 36 of a detent 38; frame 42 of a timepiece equipped with the detent escapement 28; detent spring 44; release pallet 46 carried by a plate 48 of a balance 50; impulse pallet 52.

[0012] We can see that the detent escapement 28 illustrated on the Figure 2 differs from the detent escapement 1 described above in connection with the Figure 1by the absence of the spring blade 16, replaced by a return spring 54 such as a spiral spring connected to the frame 42 of the timepiece by its last outer turn 56, and connected by its first inner turn 58 to the body 36 of the detent 38 at a point 60 where this body 36 is pivoted. Given that the body 36 of the detent 38 is pivoted, we speak of a “pivoted” detent escapement.

[0013] Yet another example of a detent escapement well known to those skilled in the art is that devised by Abraham-Louis Breguet, a brief description of which is provided in connection with figure 402 of the work published in London in 1975 by George Daniels and entitled “The Art of Breguet”, and which is reproduced in Figure 3 attached to this patent application.

[0014] The Breguet escapement is also a "pivoted" detent escapement because this detent 62 is indeed pivoted around a pivot axis 64, but this pivoted detent escapement differs mainly from other forms of execution of detent escapements by the absence, on the detent, of a detent spring, replaced by a hook 66 pivoted on a plate 68 of a balance 70 and returned by a spring 72.

[0015] Since then, other forms of detent escapements have been proposed. All these detent escapements have in common a reputation for their chronometric qualities. However, it was quickly realized that these detent escapements reacted poorly to shocks and sudden movements that cause the escape wheel to jump.

[0016] On the other hand, the leaf springs and detent springs required to operate detent escapements are long and tedious to manufacture, making them expensive. Furthermore, since these springs are very thin, they are susceptible to wear and breakage. For this reason, integrating a detent escapement into worn watches, particularly wristwatches, has always been very difficult and rarely applied.

[0017] However, given the remarkable chronometric qualities of detent escapements, several attempts have been made to make such detent escapements less sensitive to shocks and thus allow their integration into all types of timepieces and, in particular, into wristwatches.

[0018] The position in which the escape wheel is locked on the detent stop must be ensured whatever the conditions: worn watch, shocks, etc. Similarly, it is necessary to release the escape wheel so that it can give the balance a driving impulse. It is also necessary to allow the passage of the balance without influence on the detent during the alternation without impulse, then to ensure the return of the detent and its jewel in the path of the escape wheel at the end of the impulse to stop the rotation of this escape wheel.

[0019] Document EP1538491A1, in the name of the applicant, discloses a detent escapement comprising an escape wheel, a balance wheel on the axis of which is fixed a large roller, equipped with an impulse pallet and a first actuating finger, a blocker in the form of a rocker articulated on an axis, this blocker carrying a locking pallet, a second actuating finger and a feeler terminated by a beak, said escapement further comprising an elastic member acting on one of the actuating fingers to drive the other finger and actuate the blocker when the roller turns in a first direction (a) and to bypass said other finger without driving it when the roller turns in a second direction (b) opposite to the first, the axis of the balance wheel further carrying a small roller in the circular periphery of which is made a notch into which the beak of the feeler penetrates when the locking pallet is released from the escape wheel.In this document, the blocker comprises a first branch carrying the resting pallet and a second branch carrying the second actuating finger and the feeler terminated by the beak, the elastic member acting on the first actuating finger.

[0020] As understood from the above, in traditional detents, the return and locking are ensured by a spring carried by the body of the detent. This return of the detent can also be ensured by a spiral spring combined with a pivoted detent as notably described in the book "Escapement and stepper motors" mentioned above. These springs are not pre-wound, the force they oppose to the unlocking of the escape wheel in its rest position on the detent in the event of shocks applied to the clockwork is very low.

[0021] As understood from the above, in traditional triggers, the passage of the balance without influence on the trigger during the alternation without impulse is ensured by a very thin and very fragile trigger spring, generally made of gold, such as the 18 or 44 trigger springs.

[0022] In the case of the non-pivoted detent escapement shown in Figure 1, the manufacture of the detent spring 18 of the body 8 of the detent 10 is a very delicate operation. Indeed, this detent spring 18, being very small and very fragile, is difficult to manufacture. In addition, this detent body spring always provides the same elastic force, regardless of the degree of winding of the barrel spring which provides the mechanical energy necessary for the operation of the clockwork movement in which the detent escapement is installed. Consequently, when the barrel spring is weakly wound, the constant elastic force opposed by this detent spring is detrimental to the proper operation of the escapement. In particular, the escape wheel, receiving little energy from the barrel spring, has more difficulty overcoming the constant elastic force of the detent spring when it has to disengage from its engagement with the detent, which is detrimental to the isochronism qualities of the escapement.

[0023] In the case of the pivoted detent escapement visible on the Figure 2 , the manufacture and assembly of the return spring 54 on the body 36 of the trigger 38 are also very delicate and expensive operations. In addition, this solution involves a large number of components to be manufactured. Finally, in this case also, the return spring 54 of the body 36 of the trigger 38 always provides the same elastic force, regardless of the degree of winding of the barrel spring which provides the mechanical energy necessary for the operation of the clockwork movement in which the trigger escapement is installed. Consequently, when the barrel spring is weakly wound, the constant elastic force opposed by this trigger spring is detrimental to the proper functioning of the escapement.

[0024] In both cases, the manufacture of these detent springs is a very delicate operation. In addition, these detent springs, being very small and very thin, are fragile and susceptible to wear. Finally, these detent springs always provide the same elastic force, regardless of the degree of winding of the barrel spring, which provides the mechanical energy necessary for the operation of the clockwork movement in which the detent escapement is installed. Consequently, when the barrel spring is weakly wound, the constant elastic force opposed by these detent springs is detrimental to the proper functioning of the escapement.

[0025] In particular, the energy consumed by detent escapements at the lost stroke and the friction forces that must be overcome to release the escape wheel at the moment of the driving impulse are not proportional to the torque provided by the barrel spring. It therefore seemed interesting to try to do away with such springs. Summary of the invention

[0026] The present invention aims to solve the problems mentioned above and others by proposing a detent escapement providing the functions of locking the rest position on the detent of the escape wheel, releasing the escape wheel and moving the balance to its initial position by using a mechanism that is simpler than those used in the detent escapements of the prior art and whose operation is therefore more reliable.

[0027] To this end, the present invention relates to a detent escapement as defined in claim 1.

[0028] According to special embodiments of the invention: the return pallet is arranged so that, while the escape wheel continues to give the driving impulse to the impulse pallet of the balance wheel by one of its teeth, it drives the return pallet of the detent by another of its teeth, so that the rest pallet gradually enters again within the perimeter of the teeth of the escape wheel; the first and second arms of the trigger are either made in one piece or rigidly connected to each other and capable of pivoting on an axis; the first and second arms are connected to each other by means of a rivet; the first arm of the trigger carries the rest pallet against which the escape wheel is supported by one of its teeth when it is in the rest position as well as the return pallet, and the second arm carries the release pallet; the first and second arms extend in two parallel planes spaced from each other, so that the rest and return pallets on the one hand, and the release pallet on the other hand, are stepped; the rest and return pallets are arranged on either side of the pivot axis; the rest and return pallets are parallelepipedal in shape, terminated by inclined planes and extend parallel to each other;the second arm carries an anti-shock member intended to penetrate into a clearance made in the periphery of a plate of the balance wheel; the pivoting movement of the trigger is limited by an impulse stop on the one hand, and by a rest stop on the other hand, the second arm of the trigger coming into contact with the impulse stop when the escape wheel communicates a driving impulse to the balance wheel, and against the rest stop when the escape wheel returns to its rest position.

[0029] Thanks to these characteristics, the present invention provides a detent escapement whose functions of locking the rest position on the detent of the escape wheel, of releasing the escape wheel at the moment of the driving impulse and of passing the balance wheel to empty at the lost stroke are no longer ensured by a mechanism involving a detent body carrying an elastic blade and returned by a detent spring, or a pivoted detent body comprising a return spring, but by a simple hook and a spring carried by the balance wheel and cooperating with a release pallet and a return pallet carried by the detent.This avoids having to resort to these fine springs used in the detent escapements of the prior art which are very difficult to manufacture, fragile and sensitive to wear and which, by opposing a constant elastic force, increase the risk of stopping when going into idle, limit the starting of the escapement, in particular when the barrel spring is weakly wound, and harm the isochronic qualities of the detent escapements.

[0030] On the contrary, thanks to the present invention, the triggering of the impulse is ensured by a hook which, by acting on a release pallet carried by the detent, allows the escape wheel to be released from its stop on the rest pallet also carried by the detent. Similarly, the hook pivots out of the way when the balance returns to its initial position. The present invention thus makes it possible to do away with any spring playing an active role in the release of the escape wheel. The return of the hook when the stroke is lost is ensured by a simple spring which is easier to produce. This arrangement makes it possible to propose a detent escapement mechanism whose operation is much more reliable and precise.Furthermore, since, after the escape wheel is released, it directly provides its driving impulse to the balance wheel, without any spring intervening, the mechanical forces involved in the detent escapement mechanism according to the invention are always proportional. Indeed, if the barrel spring is heavily wound, it provides the escape wheel with high mechanical power thanks to which its locking torque on the detent provided by the pulling device is high and, in turn, the escape wheel provides a high driving impulse to the regulating device. Conversely, if the barrel spring is lightly wound, the escape wheel receives low mechanical power, so that its locking torque on the detent provided by the pulling device is low, this mechanical power then being directly transmitted to the balance wheel which will be lightly stressed.The locking torque of the escape wheel on the detent being thus always proportional to the torque provided by the barrel spring, the oscillation frequency of the balance will therefore constantly adapt according to the degree of winding of the barrel spring, which makes it possible to guarantee the maintenance of the isochronism of the detent escapement according to the invention whatever the conditions of winding of the barrel spring. Furthermore, the detent is arranged so that, by cooperation with the escape wheel, its return to the position in which it again blocks the escape wheel after the latter has finished giving the driving impulse to the balance is assisted by said escape wheel.Thus, the return of the detent to its position blocking the escape wheel is achieved by simple cooperation between this detent and this escape wheel, without the aid of any spring, which simplifies the manufacture of the detent escapement according to the invention and makes its operation much more reliable. Brief description of the figures

[0031] Other characteristics and advantages of the present invention will emerge more clearly from the following detailed description of an exemplary embodiment of a detent escapement according to the invention, this example being given purely for illustrative and non-limiting purposes only in conjunction with the appended drawing in which: there Figure 1 , already cited, is a schematic representation of a detent escapement according to the prior art comprising a spring blade and a detent spring; the Figure 2, already cited, is a representation of a first embodiment of a pivoted detent escapement according to the prior art; -the Figure 3 , already cited, is a representation of a second form of execution of a pivoted detent escapement according to the prior art also called Breguet detent; Figure 4 is a perspective view of the detent escapement according to the invention in its complete state; Figure 5A is a schematic representation of the detent escapement according to the invention in its rest position; Figure 5B is a view analogous to that of the Figure 5A , the detent escapement being in a position in which the escape wheel begins to disengage from its engagement with the locking pallet and can give a driving impulse to the balance; Figure 5C is a view analogous to that of the Figure 5B on which the escape wheel turns and transmits its driving torque to the balance wheel's impulse pallet; Figure 5Dis a view analogous to that of the Figure 5C , the escape wheel continuing to provide the driving impulse to the balance wheel while driving the trigger return pallet; Figure 5E is a view analogous to that of the Figure 5D on which the escape wheel finishes giving the driving impulse to the balance, while the rest pallet is again within the perimeter of the teeth of the escape wheel; the Figure 5F is a view analogous to that of the Figure 5E on which the escape wheel is at rest, while the balance wheel pivots clockwise and makes its idle alternation also called lost stroke; the Figure 6 illustrates, in the case of a prior art detent escapement of the type illustrated in Figure 1 , the angle traveled by the balance wheel and the trajectory described by the trigger spring during the lost shot, and the Figure 7illustrates, in the case of a detent escapement according to the invention, the angle traveled by the balance wheel plate and the trajectory described by the pivoting hook during the lost stroke. Detailed description of an embodiment of the invention

[0032] The present invention proceeds from the general inventive idea which consists of providing a detent escapement in which the release of the escape wheel to give the balance the driving impulse during the first alternation of an oscillation, and the return, without energy input, of this balance to its initial position during the second alternation, also called "lost stroke", of the same oscillation, are carried out without assistance from a spring carried by the detent and without a return spring. Thanks to the invention, it is thus possible to do without the springs conventionally used in detent escapements which are known to be very delicate to machine, fragile and sensitive to wear. Furthermore, given that the escape wheel is in direct contact with the balance, there is a constant concordance between the mechanical energy supplied by the barrel spring and the energy supplied to the balance.If the barrel spring is heavily wound, the escape wheel provides the balance with a high mechanical impulse, the oscillation amplitude of the balance is also high and the force consumed for the release of the escape wheel is high; conversely, if the barrel spring is lightly wound, the escape wheel provides the balance with a low-intensity mechanical impulse, so that the oscillation amplitude of the balance weakens as does the force consumed for the release of the escape wheel. Therefore, for its operation, the detent escapement according to the invention does not oppose a high mechanical resistance when the barrel spring is lightly wound, so that its isochronic properties are not affected.Furthermore, according to another aspect of the invention, the return of the detent to the position in which it ensures the blocking of the escape wheel after the latter has provided the driving impulse to the balance is assisted by the escape wheel itself, without the need for a spring. The manufacture of the spiral escapement according to the invention is therefore facilitated and the reliability of its operation is significantly increased.

[0033] Designated by the general numerical reference 74, the detent escapement shown in the Figure 4is intended to be mounted in a timepiece, in particular a wristwatch (not shown). This detent escapement 74 notably comprises an escape wheel 76 provided with a plurality of regularly spaced teeth 78. This escape wheel 76 is conventionally driven by the gear train 80 of the timepiece which receives its driving force from one or more barrel springs (not shown in the drawing).

[0034] The detent escapement 74 is completed by a balance wheel 82 mounted on an axis 84 and whose oscillations are maintained by a spiral spring 88. On the side of its last turn inside 90, the spiral spring 88 is conventionally fixed on the axis 84 of the balance wheel 82 by means of a collet 92, while on the side of its last turn outside 94, the spiral spring 88 is fixed to a stud 96.

[0035] As visible on the Figure 5A, the balance 82 is equipped with an impulse pallet 98 thanks to which the balance 82 receives driving impulses via the teeth 78 of the escape wheel 76. This impulse pallet 98 is preferably but not limited to the form of a small piece of ruby, sapphire, garnet or other in the shape of a parallelepiped, embedded in the balance 82 and terminated at its free end by an inclined plane 100.

[0036] We also see at the Figure 5Aa hook 102 pivotally mounted on the balance 82 and held in abutment against a stop 104 by an elastic member 106. In the example shown in the drawing, the elastic member 106 is carried by the balance 82. This elastic member 106 of the simple spring type plays the role of the detent spring in conventional detent escapements. Its function is to allow the body of the detent to disengage from its engagement with the escape wheel at the start of the driving impulse. It is observed once again that the detent escapement according to the invention does not otherwise include a return spring

[0037] According to the invention, the detent escapement 74 further comprises a detent 108. This detent 108 is formed of a first and a second arm, respectively 110 and 112, these first and second arms 110 and 112 being rigidly connected to each other, for example by means of a rivet 114, and being able to pivot on an axis 116. In the example shown in the drawing, the first and second arms 110 and 112 are manufactured separately from each other, then assembled to each other for example by riveting. It goes without saying that these first and second arms 110 and 112 can just as easily be manufactured in a single piece, for example by molding.

[0038] The first arm 110 carries a rest pallet 118 at a first end, and a return pallet 120 at a second end. These rest pallets 118 and return pallets 120 are arranged on either side of the pivot axis 116 of the trigger 108; they are preferably in the form of two small pieces of ruby, sapphire, garnet or other in the shape of a parallelepiped and are embedded in each of the ends of the first arm 110. These rest pallets 118 and return pallets 120 are terminated by inclined planes 122 and 124 via which they cooperate with the teeth 78 of the escape wheel 76. These rest pallets 118 and return pallets 120 preferably but not necessarily extend parallel to each other.

[0039] As for the second arm 112, it carries at one of its ends a release pallet 126 of the same type as the other pallets described above and terminated at its free end by an inclined plane 128. This second arm 112 also carries an anti-shock member 130.

[0040] There Figure 4 further shows that the balance 82 comprises a plate 132 in the periphery of which a clearance 134 is made into which the anti-shock member 130 is brought to penetrate under conditions which will be detailed below. It is also observed that the first and second arms 110 and 112 extend in two parallel planes spaced apart from each other, so that the rest and return pallets 118 and 120 on the one hand, and the release pallet 126 on the other hand are stepped.

[0041] Finally, the movement of the first arm 110 and therefore of the trigger 108 as a whole is limited by an impulse stop 136 on the one hand, and by a rest stop 138 on the other hand.

[0042] To the Figure 5A , the escape wheel 76 has turned clockwise and is in its rest position in which it is supported by one of its teeth 78 against the rest pallet 118 carried by the first arm 110 of the trigger 108. As for the balance 82, it has turned counterclockwise, so that its pivoting hook 102 has come into contact with the release pallet 126 of the second arm 112.

[0043] To the Figure 5B , the balance wheel 82 always tends to rotate counterclockwise, so that its pivoting hook 102 pushes the release pallet 126 away from the second arm 112, which causes the entire trigger 108 to pivot clockwise. Under the effect of this pivoting, the locking pallet 118 is released from its engagement with the tooth 78 of the escape wheel 76, which allows the latter to rotate freely clockwise.

[0044] To the Figure 5C , the escape wheel 76 rotates freely clockwise and transmits, via one of its teeth 78, a driving impulse to the impulse pallet 98, which rotates the balance 82 counterclockwise.

[0045] To the Figure 5D , the escape wheel 76 continues to give the driving impulse to the impulse pallet 98 of the balance 82 by one of its teeth 78, while by another of its teeth 78 it drives the return pallet 120 of the detent 108. The whole of the detent 108 thus tends to turn in the counterclockwise direction, so that the rest pallet 118 gradually penetrates again into the perimeter of the teeth 78 of the escape wheel 76. It is also observed that, in the position illustrated in Figure 5D, the anti-shock member 130 is located at the bottom of the clearance 134 made in the plate 132 carried by the balance wheel 82, this in order not to hinder the pivoting of the trigger 108 during the impulse phase which extends from the Figure 5A to the Figure 5E . During the remainder of the oscillation of the balance wheel 130, the function of this anti-shock member 130 is, by contact with the plate 132 of the balance wheel 130, to limit the pivoting of the detent 108 in the event of a shock applied to the clockwork movement and to prevent the involuntary unlocking of the escape wheel 76 when the latter is in its rest position on the detent 108.

[0046] To the Figure 5E , the escape wheel 76 finishes giving the driving impulse to the impulse pallet 98 of the balance 82 and the rest pallet 118 is again within the perimeter of the teeth 78 of the escape wheel 76.

[0047] To the Figure 5F, the escape wheel 76 is at rest, supported by one of its teeth 78 on the rest pallet 118. From this moment, the escape wheel 76 is held against the rest pallet 118 with a certain force. Il This is a safety device for holding the escape wheel 76 while the balance wheel 82 performs its idle alternation, also called a lost stroke, a device called a draw which provides resistance to the release of the locking pallet 118 during shocks applied to the timepiece. The draw is generally defined by an angle α formed by a rest plane 140 of the rest pallet 118 and a perpendicular 142 raised on a radius 144 of the trigger 108, at the point of contact 146 of the tooth 78 and the rest pallet 118. The value of the angle αof draw is preferably but not limited to between 5° and 20°, knowing that the higher this value, the better the escapement's immunity to shocks and accelerations, but the more difficult it will be for the escape wheel to free itself from its grip with the detent at the start of the driving impulse, which is detrimental to the mechanical efficiency and the isochronsime of the escapement. Conversely, the lower the value of the angle αThe greater the pull force, the easier it will be for the escape wheel to escape from the engagement with the detent at the start of the driving impulse and therefore the better the efficiency and isochronism will be. On the other hand, the resistance of the detent escapement according to the invention to shocks will be lower. As for the balance 82, it pivots clockwise and makes its idle alternation also called lost stroke. During the return movement of the balance 82, the pivoting hook 102 disappears when it passes at the height of the release pallet 126 by performing a pivoting movement along a radius close to that of the balance 82, so that the passage of the balance 82 has no influence on the detent 108 during said alternation without impulse. Indeed, as illustrated in Figure 6, in the case of a detent escapement of the prior art, during the lost stroke, given that the detent spring 18 deforms along a large radius and that its free end travels a trajectory 148 substantially tangent to the external diameter of the plate 22 of the balance 24, this plate 22 travels an angle β of 13.8°. On the contrary, in accordance with the invention (see Figure 7), the pivot center of the pivoting hook 102 is offset from a center line 150 which joins the pivot center of the detent 108 to the pivot center of the balance 102 and the free end of the pivoting hook 102 pivots along a smaller radius than the radius along which the detent spring 18 of the prior art deforms and describes a trajectory 152 which is more oriented towards the center of the balance wheel plate 82. Consequently, the angle y traveled by the balance wheel plate 82 during the lost stroke is much smaller, typically of the order of 2.5° in the present case, so that the detent escapement according to the invention is much less disturbed, which has a beneficial effect on the isochronism of the escapement.

[0048] IlIt goes without saying that the present invention is not limited to the embodiment which has just been described and that various modifications and simple variants can be envisaged by those skilled in the art without departing from the scope of the invention as defined by the appended claims. It will be understood in particular that instead of the rest pallets 118, return pallets 120 and release pallets 126, the trigger 108 could be provided with surfaces made of the same material as them and by which it would cooperate directly with the escape wheel 76 and the balance 82. Nomenclature

[0049] 1. Detent escapement 2. Escape wheel 4. Teeth 6. Jewel 8. Body 10. Detent 12. Beak 14. Frame 16. Spring blade 18. Detent spring 20. Release pallet 22. Plate 24. Balance 26. Impulse pallet 28. Detent escapement 30. Escape wheel 32. Teeth 34. Jewel 36. Body 38. Detent 42. Frame 44. Detent spring 46. Release pallet 48. Plate 50. Balance 52. Impulse pallet 54. Return spring 56. Last outer turn 58. First inner turn 60. Point 62. Detent 64. Pivot pin 66. Hook 68. Plate 70. Balance 72. Spring 74. Detent escapement 76. Escape wheel 78. Escape wheel teeth 80. Clockwork 82. Balance wheel 84. Axle 88. Spiral spring 90. Last coil inside 92. Collet 94. Last coil outside 96. Stud 98. Impulse pallet 100. Inclined plane 102. Pivoting hook 104. Stop 106. Elastic member 108. Detent 110. First arm 112. Second arm 114.Rivet 116. Pivot axis 118. Resting pallet 120. Return pallet 122. Inclined plane 124. Inclined plane 126. Release pallet 128. Inclined plane 130. Anti-shock member 132. Plate 134. Release 136. Impulse stop 138. Resting stop. α Angle of draw 140. Plane of rest 142. Perpendicular 144. Radius 146. Point of contact 148. Trajectory β . Angle 150. Center line 152. Trajectory γ . Corner

Claims

1. A detent escapement provided to regulate the functioning of a horology movement, this detent escapement (74) comprising an escape wheel (76) with a plurality of teeth (78) regularly spaced along a perimeter and a balance (82), the balance (82) being equipped with an impulse pallet (98) by means of which this balance (82) receives driving impulses via the teeth (78) of the escape wheel (76), the balance (82) being moved by an oscillating movement during which it performs, for each oscillation, a vibration during which it receives a driving impulse and a vibration with no driving impulse, the detent escapement (74) also comprising a hook (102) pivotally mounted on the balance (82) and kept pressed against a stop (104) by a resilient organ (106), the detent escapement (74) being completed by a detent (108) which is capable of pivoting and which comprises a first arm (110) which collaborates with the escape wheel (76) to ensure the blocking of the latter just before the start of the driving impulse, as well as a second arm (112) which collaborates with the hook (102) of the balance (82) to allow the escape wheel (76) to disengage from its engagement with the first arm (112) at the start of the driving impulse, and which limits the pivoting of this detent (108) to only part of the oscillation of the balance (82), the detent (108) also being arranged so that, by cooperation with the escape wheel (76), its return to the position in which it again blocks the escape wheel (76) after the latter has finished providing the driving impulse to the balance (82) is assisted by said escape wheel, the detent escapement lastly comprising a drawing device which opposes a resistance to the unlocking of the escape wheel (76) during shocks applied to the horological movement when the latter is in its lock position on the detent (108); a detent escapement in which the first arm (110) of the detent (108) carries on the one hand a lock pallet (118) against which the escape wheel (76) presses with one of its teeth (78) just before the start of a driving impulse, and the second arm (112) of the detent carries a unlocking pallet (126) against which the pivoting hook (102) of the balance (82) presses just before the start of the driving impulse, the pivoting hook (102) being arranged so as to push back the unlocking pallet (126) and to pivot the detent (108) at the start of the vibration stage of the balance (82) where the impulse takes place, so that the lock pallet (118) disengages from the tooth (78) of the escape wheel (76) with which it is engaged and allows this escape wheel (76) to provide the driving impulse to the balance (82), and the pivoting hook (102) being arranged so that, during the impulse-free vibration of the balance (82), it is retracted by performing a pivoting movement when it passes by the unlocking pallet (126), so that the passage of the balance (82) has no influence on the detent (108) during said impulse-free vibration, the detent (108) also carrying a return pallet (120) arranged so that the lock pallet (118) again gradually penetrates the perimeter of the teeth (78) of the escape wheel (76) when the latter finishes providing the driving impulse to the impulse pallet (98) of the balance.

2. The detent escapement according to claim 1, characterised in that the return pallet (120) is arranged so that, while the escape wheel (76) continues to provide the driving impulse to the impulse pallet (98) of the balance (82) with one of its teeth (78), it drives the return pallet (120) of the detent (108) with another of its teeth (78), so that the lock pallet (118) again gradually penetrates the perimeter of the teeth (78) of the escape wheel (76).

3. The detent escapement according to any of claims 1 or 2, characterised in that the first arm (110) and the second arm (112) are rigidly connected to each other and form an assembly capable of pivoting on an axis (116).

4. The detent escapement according to claim 3, characterised in that the first and second arms (110, 112) are connected to each other by means of a rivet (114).

5. The detent escapement according to claim 3, characterised in that the first and second arms (110, 112) are made in one piece.

6. The detent escapement according to any of claims 3 to 5, characterised in that the first and second arms (110, 112) extend in two planes which are parallel and distant from each other, so that the lock (118) and return (120) pallets, on the one hand, and the unlocking pallet (126) on the other hand, are stepped.

7. The detent escapement according to any of claims 3 to 6, characterised in that the lock (118) and return (120) pallets are arranged on either side of the pivot axis (116).

8. The detent escapement according to any of claims 3 to 7, characterised in that the lock (118) and return (120) pallets are parallelepipedal in shape, ending in inclined planes (122, 124) and extend parallel to each other.

9. The detent escapement according to any of claims 3 to 8, characterised in that the second arm (112) carries a shock-resistant organ (130) intended to penetrate a countersink (134) formed in the periphery of a balance (82) plate (132) when the escape wheel (76) finishes providing the driving impulse to the balance (82).

10. The detent escapement according to any of claims 3 to 9, characterised in that the pivoting travel of the detent (108) is limited by an impulse stop (136) on the one hand, and by a lock stop (138) on the other hand, the detent (108) abutting against the impulse stop (136) when the escape wheel (76) transmits a driving impulse to the balance (82), and the detent (108) abutting against the lock stop (138) when the escape wheel (76) returns to its lock position.

11. The detent escapement according to any of claims 9 or 10, characterised in that the resilient organ (106) is carried by the plate (132) of the balance (82).

12. The detent escapement according to any of claims 1 to 11, characterised in that the drawing device is formed by the lock pallet (118) a lock plane (140) of which forms an angle α with a perpendicular (142) elevated on a radius (144) of the detent (108), at the point of contact (146) of the tooth (78) and the lock pallet (118).

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