FR2921597A1 - Pumping control mechanism for controlling height adjustment of front seat base of vehicle, has driving disc pads including gear teeth that are provided with truncated tooth whose free end forms flat spot between lateral flanks of tooth - Google Patents

Abstract

The mechanism (6) has a driving device (23) including two driving disc pads (32, 33) elastically biased towards a toothed crown (19), where the disc pads are in the form of metallic plates. The disc pads are arranged such that ends (41, 42) of external gear teeth (34) of the disc pads are arranged nearer to the crown and separated from the crown, respectively, when an actuating unit (29) is in an angular rest position (N). The gear teeth is provided with a truncated tooth (43) whose free end forms a flat spot between outer lateral flanks of the tooth.

Description

Pumping control mechanism and vehicle seat comprising such a mechanism.

The present invention relates to pumping control mechanisms and vehicle seats having such mechanisms. More particularly, the invention relates to a pumping control mechanism for a vehicle seat, comprising. First and second armatures mounted rotatably relative to one another about an axis of rotation, the second armature comprising a ring gear centered on the axis of rotation, an actuating member pivotally mounted by Relative to the first armature about the axis of rotation and being elastically biased towards an angular rest position, said actuating member being movable, from its rest position, into first and second angular sectors of both sides other of said resting position, and first and second driving grains each having a toothing adapted to engage the toothed ring of the second armature, each driving wire being pivotally mounted on the body of the second armature actuating about a pivot axis offset from the axis of rotation of the actuating member, the first drive being adapted to engage the tooth crown e only when the actuator rotates in the first angular sector and in a first angular direction, and the second drive is adapted to engage the ring gear only when the actuator rotates in the second angular sector and in a second angular direction opposite to the first direction, the toothing of the first driving grain extending in the first angular direction between the first and second ends and the toothing of the second driving grain extending in the second angular direction between first and second ends, and the teeth of the first and second drive grains each having a series of teeth which comprise two flanks converging towards a free end, the first and second drive grains being biased elastically. to the ring gear and being arranged so that when the actuating member is positio n of rest, the first end of the teeth of the first and second drive grains is in the immediate vicinity of the ring gear and the second end of the teeth of the first and second drive grains is spaced from said ring gear. Document FR-A-2,750,186 describes an example of a hinge mechanism of this type, which gives satisfaction. However, it has appeared useful to further improve the control mechanisms of this type, so as to ensure a better accuracy of the angular position of the rest of the actuating member.

For this purpose, a control mechanism of the kind in question is characterized in that the teeth of the first and second drive grains comprise, at their first end, at least one truncated tooth whose free end forms a flat between the two. flanks of said tooth. Thanks to these provisions, it prevents the teeth of the drive grains do not hinder the return of the actuating member in the rest position, which ensures a high accuracy of said rest position.

In preferred embodiments of the control mechanism according to the invention, one or more of the following arrangements may also be used: the teeth of the first and second driving grains comprise, at their first end, several truncated teeth whose free end forms a flat between the two sides of said tooth; said truncated teeth of each toothing comprise a first truncated tooth located at the first end of said toothing, said first truncated tooth having an external flank turned away from the second end of the toothing to which the first truncated tooth belongs, the first and second driving grains being arranged so that, when the actuating member is in the rest position, the outer flank of said first truncated tooth constitutes a single point of support of each drive grain against the crown toothed; said outer flank of the first truncated tooth forms with the flat of said first truncated tooth an angle of between 100 and 120 degrees; each toothing comprises a plurality of additional truncated teeth adjacent to the first truncated tooth, said additional truncated teeth having a decreasing tooth height to the first truncated tooth; said additional truncated teeth are three in number; - The teeth of the first and second drive grains further comprise at least one uncut tooth, whose flanks converge towards a free tip end; the first armature comprises at least one guide ramp adapted to prevent the first driving wheel from coming into engagement with the ring gear of the second armature when the actuating member is in the second angular sector and to prevent the second drive grain to engage the toothed crown of the second armature when the actuator is in the first angular sector; the control device further comprises first and second locking pawls which are pivotally mounted on the first armature and which are urged towards a locking position where said first and second locking pawls engage with the ring gear , the first locking pawl being adapted, when in the locking position, to block a rotation of the second armature relative to the first armature in the first angular direction and to allow a rotation of the second armature in the second angular direction , and the second locking pawl being adapted, when in the locking position, to block a rotation of the second armature relative to the first armature in the second angular direction and to allow a rotation of the second armature in the first direction angular, the actuating member is adapted to move the first lock ratchet in an erased position where it does not cooperate with the ring gear when said actuating member is moved in the first angular sector, in the first angular direction, and said actuating member is adapted to move the second locking pawl in an erased position where it does not cooperate with the ring gear when said actuating member is moved in the second angular sector in the second angular direction. Furthermore, the invention also relates to a vehicle seat comprising two parts movable relative to each other in a relative movement controlled by a control mechanism as defined above. Other features and advantages of the invention will become apparent from the following description of one of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings. In the drawings: FIG. 1 is a schematic view of a vehicle seat equipped with a pumping control mechanism according to one embodiment of the invention, FIG. 2 is a front view of the mechanism of the invention. FIG. 3 is an exploded perspective view showing the control mechanism of FIG. 2 seen in two opposite directions; FIG. 5 is a front view showing the interior of the seat. FIG. and the second armature of the control mechanism of FIGS. 3 and 4; FIG. 5a is a view of the detail of FIG. 5; FIGS. 6 and 6a are views similar to FIGS. 5 and 5a, showing the mechanism of FIG. control when one of the driving grains begins to engage the toothed crown of the second armature, - Figures 7 and 7a are views similar to Figures 5 and 5a, showing the control mechanism when the grain drive is fully engaged with the toothed crown of the second armature, and - Figures 8 and 8a are views similar to Figures 5 and 5a, showing the control mechanism when the drive wheel rotates the second armature. In the different figures, the same references designate identical or similar elements. Figure 1 shows a front seat 1 of a motor vehicle, which comprises a backrest 2 mounted on a seat which seat is itself mounted on the floor 4 of the vehicle, for example by means of slides 5. The seat 3 is connected to the slideways 5 by a raising mechanism comprising, for example, raising rods 6a each rotatably mounted on the movable section of one of the slides 5 and on the frame of the seat 3. This raising mechanism is controlled by a control mechanism 6 which drives at least one of the connecting rods 6a to adjust the height of the seat 3 upwards in the direction H or downwards in the direction B. The control mechanism 6 is actuated by a handle 7 which is pivotally mounted on a transverse axis of rotation Y and biased elastically to an angular position of rest N. From this rest position N, the handle 7 can be moved in a first sector If, in a first angular direction Al, which has the effect of raising the seat 3 in the direction H. Moreover, from the rest position N, the handle 7 can also be moved in a second angular sector S2, in a second angular direction A2 opposite the first angular direction A1, so as to lower the seat 3 in the direction B. Each return of the handle 7 to its rest position N, the seat 3 remains stationary. The aforementioned pump control mechanism 6 is visible in particular in FIGS. 2 to 5a in the rest position of the handle 7. As more particularly shown in FIGS. 3 and 4, the control mechanism 6 comprises first and second armatures. 8.9, which may be for example in the form of two disk-shaped metal flanges, which are rotatably mounted relative to one another about the axis of rotation Y and which can be connected to one another. to one another for example by means of a crimped metal ring 10.

The first frame 8 can be secured to a frame of the vehicle seat, for example a portion of the frame of the seat 3, by means of metal tabs 11,12. Each of the lugs 11,12 may comprise for example a mounting plate, respectively lla, 12a, fixed to the corresponding frame of the seat (for example the frame of the seat 2) by screwing, riveting, welding or other. This plate 11a, 12a is extended along the Y axis by a projection, respectively 11b, 12b which matches the outer shape of the crimped ring 10. This projection is itself extended, radially inwards, by a rim, respectively 11c, 12c, which partially covers the outer face of the first armature and is fixed to said outer face for example by welding or other. The radially inner edge of the rim 11c is extended, axially along the Y axis, opposite the first armature 8, by a finger 11d whose utility will be seen further, while the rim 12c is extended, in the same direction, by a hook 12d which is open radially outward and whose utility will also be explained later. The two fastening lugs 11, 12 may be arranged for example in substantially diametrically opposite positions with respect to the Y axis. The first armature 8 is pierced by a central circular orifice 13 centered along the Y axis, which serves bearing for a control shaft 14, metal or other. This control shaft 14 comprises: - an outer portion 14a of square section or other, which protrudes out of the control mechanism 6 and on which is engaged the handle 7 mentioned above, - an intermediate portion 14b with circular section, which pivots in the orifice 13 of the first armature, - and an inner portion 14c of substantially rectangular section, extending along a transverse axis Y 'perpendicular to the axis of rotation Y. The first armature 8 further comprises a through-light 15 in an arc of a circle, centered on the axis of rotation Y, whose central portion is arranged in correspondence with the aforementioned finger lld. The first armature 8 further comprises, on its inner face, a hollow stamped part 16 obtained for example by the so-called technique of semi-cutting or thin cutting. The outer edge of this stamped hollow portion 16 forms a guide ramp 17 whose utility will be seen further. This guide ramp comprises: a central portion 17a in an arc centered on the axis of rotation Y, and two lateral portions 17b surrounding said central portion, these lateral portions themselves being in the form of circular arcs centered. on the Y axis, but of larger diameter than the central portion 17a, so that the guide ramp 17 forms two projections 17c between the central portion 17a and the side portions 17b. Finally, the first frame 8 internally comprises three projecting circular pins 18, 18a whose utility will be seen further.

The second armature 9, meanwhile, comprises, on the side of the first armature, a ring gear 19 which is centered on the Y axis and whose circular toothing is oriented radially inwards. The second armature 9 also comprises a central through hole 20, which is centered on the axis of rotation Y and which may have for example a square shape or the like, and in which is engaged the central shaft 21 of an output gear 22 which may for example engrainer with an arcuate teeth integral with one of the aforementioned raising rods 6a. In the interior space left free between the first and second frames 8, 9 is disposed a grain drive device 23, which is clearly visible in Figures 3 to 5.

This drive device 23 comprises an actuating member 24 which may for example be in the form of a sheet metal plate extending in a plane perpendicular to the axis of rotation Y. The actuating member 24 is pierced by a central orifice 25 of substantially rectangular shape, which extends along the aforementioned transverse axis Y 'and in which is engaged the inner portion 14c of the control shaft 14. The inner portion 14c of the shaft 14 is engaged in the central orifice 25 with a certain clearance, for example of the order of a few millimeters, in the direction of the transverse axis Y ', and substantially without play in the direction of a Y axis " perpendicular to the aforementioned Y, Y 'axes (see Fig. 5) The actuating member 24 has a shape symmetrical with respect to the (Y, Y ") plane and comprises in the example considered here: - an edge 26 substantially rectilinear, - two rounded cam edges 27 extending straight edge 26 to s the two ends, these cam edges 27 being diametrically opposed to the Y axis, substantially along the transverse axis Y ', - and a head 28 disposed in the extension of the cam edges 27 opposite the edge rectilinear 26, this head 28 comprising two substantially circular outer cutouts 29 and a central through hole 30.

The head 28 is further extended by a finger 31 which extends along the Y axis through the light 15 of the first armature 8. When the control mechanism 6 is in the rest position, the finger 31 is located in correspondence with the finger lld of the leg 11 mentioned above. The driving device 23 further comprises first and second driving grains 32, 33 which are each in the form of a metal plate extending in the plane of the actuating member 24 and which comprise each an external toothing 34 adapted to engage with the ring gear 19 of the second armature (see Figures 5 and 5a).

Each of the driving grains 32, 33 is pivotally mounted on the actuating member 24 about a pivot axis 35 parallel to the axis of rotation Y but offset with respect thereto. In the example considered here, the pivot axes 35 are the central axes of the circular cutouts 29 of the actuating member, and the drive grains 32, 33 each comprise a peduncle 36 with a circular contour which is fitted into the one of the circular cutouts 29 of the actuating member to allow the pivoting of said grains 32, 33.

The first driving grain 32 extends in the first angular direction Al from its peduncle 36 to its external toothing 34. Similarly, the second drive grain 33 extends in the second angular direction A2 from its peduncle 36 to its external toothing 34.

Each of the driving grains 33, 34 further comprises a protruding pin 37 which extends towards the first armature 8 and which is adapted to bear against the guide ramp 17 of said first armature. The two drive grains 32, 33 are resiliently biased towards the ring gear 19, for example by means of a single spring wire 38 comprising: a folded central portion 39 (see FIG. 3) engaged in the orifice 30 mentioned above of the actuating member 5, and two lateral branches 40 bearing against the protruding pins 37 of the drive grains to urge them substantially radially outwards. As shown in FIG. 5, the toothing 34 of the first driving grain 32 extends in the first angular direction A1 from a first end 41 to a second end 42. Likewise, the toothing 34 of the second drive grain 33 extending in the second angular direction A2, from a first end 41 to a second end 42. For each of the drive grains 32, 33, the first end 41 of the toothing 34 comprises a first tooth 43 which conventionally comprises two lateral flanks 44 converging towards a free end. This free end is here formed by a flat 45 which is flanked by the two flanks 44, whereas a normal tooth would comprise a free tip-shaped end, without flat between the two lateral flanks 44. In other words, the first tooth 43 is truncated, so that it has a tooth height less than the height of a normal tooth of triangular shape. In the particular example shown in the drawings, the flat portion 45 of the first truncated tooth 43 is not oriented substantially radially with respect to the Y axis, but radially outwardly in the direction of removal. relative to the second end 42 of the toothing. Thus, the angle α between the outer flank 44 of the first truncated tooth (i.e. the flank of the first tooth which is oriented opposite the second end 42 of the toothing) and the flats 45 may be for example between 100 and 120 degrees and be in particular of the order of 110 degrees. This arrangement makes it possible, on the one hand, for the outer flank 44 of the first tooth 43 to have a surface sufficient to bear against one of the teeth of the ring gear 19 of the second armature when the actuating member is in the position of rest and on the other hand, to allow a good escape of the first tooth relative to said ring gear 19 when the first tooth 43 moves along said ring gear by ratchet effect during the return of the body of actuation 24 to its rest position N, as will be explained below. The toothing 34 of each driving grain 32, 33 may further comprise, as in the example shown here, one or more additional truncated teeth adjacent to the first truncated tooth 43. In the example shown in the drawings, these teeth truncated additional 46, 47, 48 are three, and the flat 45 of each of these additional truncated teeth is oriented radially relative to a central axis respectively Y1 for the first drive grain 32 and Y2 for the second grain training 33 (see Figure 5).

These central axes Y1, Y2 may be close to the axis of rotation Y but offset laterally on either side of this axis of rotation Y along the transverse axis Y '(the lateral offset between the axes Y1, Y2 and the Y axis may for example be of the order of a few millimeters). Thus, the additional truncated teeth 46, 47, 48 have a decreasing tooth height towards the first truncated tooth 43. The sidewall 44 of the first truncated tooth 43 which is adjacent to the additional truncated tooth 46 can moreover be in line with the flats 45 of said additional truncated teeth 46, 47, 48. In other words, the upper end of this lateral flank 44 of the first truncated tooth 43 is located on the same arc (centered on the axes Y1 or Y2) as the flats. 45 of said additional truncated teeth 46, 47, 48. Finally, in the example considered here, the toothing 34 of each driving grain 32, 33 further comprises a plurality of untruncated teeth 49, whose lateral flanks 44 converge towards one end. free 50 shaped tip. These uncut teeth 49, which are located towards the second end 42 of the toothing 34 are three in the example shown in the drawings. In the rest position of the control mechanism 6, as represented in FIGS. 5 and 5a, the external lateral flanks 44 of the first truncated teeth 43 of the two driving grains 32, 33 are thus each bearing against a tooth of the crown. toothed 19, and the free ends 45, 50 of the other teeth of each toothing 34 rie are not in contact with the ring gear 19 and gradually deviate from said ring gear 19 to the second end 42 of the toothing 34. Thus, the outer flank 44 of the first tooth 43 of each toothing 34 is the only point of contact between this toothing and the ring gear 19, which prevents jamming and ensures that the actuating member 24 and the handle 7 are held precisely in their rest position N, under the effect of a spring 51 which is clearly visible in Figures 2 to 4. This spring 51 may for example be a spring wire wound substantially circular around e the axis of rotation Y between two bent ends 52. This spring wire 51 can be held against the outer face of the first armature 8 by the above-mentioned hook 12d and by the finger 11 also mentioned above, said spring wire 51 passing to the outside of the finger 11d and the bent ends 52 of the spring wire passing on either side of the fingers 11d and 31l. The fingers 11d, 31 may comprise an enlarged free end which cooperates with the bent ends 52 of the spring wire 51 to maintain in place the spring wire against the outer face of the first frame 8. Finally, as shown in Figures 3 to 5, the drive device 23 further comprises first and second locking pawls 53, 54 which are pivotally mounted on the first armature 8 around two axes 55 parallel to the axis of rotation Y but offset with respect thereto. The locking pawls 53, 54 may be in the form of sheet metal plates disposed in the same plane as the actuating member 24, and may each comprise a circular cutout 56 interlocked on one of the pins 18 of the first frame. The first locking pawl 53 extends in the second angular direction A2 from its pivot axis 55 to a free end bearing an external toothing 57 adapted to engage with the ring gear 19 of the second armature: when the first locking pawl 53 is engaged, it allows a pivoting of the second armature 9 in the second angular direction A2, but prohibits the pivoting of the second armature 9 in the first angular direction Al, by the bracing effect of said first ratchet locking. Similarly, the second locking pawl 54 extends in the first angular direction Al from its pivot axis 55 to a free end bearing an external toothing 57 which is adapted to engage with the ring gear 19: when the second locking pawl 54 is in engagement, it thus allows a pivoting of the second armature 9 in the first angular direction A1, but prohibits a pivoting of said second armature in the second angular direction A2.

The two locking pawls 53, 54 are elastically biased towards a locking position or their teeth 57 are engaged with the ring gear 19. In the example shown in the drawings, this elastic biasing is obtained by means of a spring. blade 58 which may for example have a central portion 58a V-shaped, open towards the axis of rotation Y and bearing against the pin 18a of the first frame, this central portion 58a being extended by two lateral branches 58b which are supported radially outwards against the locking pawls 53, 54. Finally, each locking pawl 53, 54 has, at an end opposite its teeth 57, a heel 59 which bears against one of the cam surfaces 27 of the actuating member, so that the cam surfaces 27 of the actuating member can selectively unlock one or other of the locking pawls 53, 54 by pressing the said heels 59, as will be explained below. The control mechanism just described works as follows. When a user actuates the handle 7 of the control mechanism in the second angular direction A2 from the rest position N, as shown in FIGS. 6 and 6a, the pivoting of the actuating member 24 displaces the second grain 33 to a position of engagement with the ring gear 19, so that the outer flank of the first truncated tooth 43 of the second drive grain slides against the side of the ring gear 19 against which it was in support , until said first truncated tooth 43 is fully engaged between two teeth of the ring gear 19. The pin 37 of the second drive beam is then facing the corresponding lateral portion 17b of the guide ramp 17, which does not interfere with this pin 37. During this first phase of the movement, which may correspond for example to a pivoting of about 2 ° relative to the rest position N, the second driving grain 33 is thus partially engaged with the ring gear 19. At the same time, the pin 37 of the first drive beam 32 cooperates with the corresponding projection 17c of the guide ramp to rotate said first drive gear 32 around its pivot axis 35 to an erased position where the toothing 34 of this first drive grain no longer cooperates with the ring gear 19. In the following movement that is to say when the actuating member continues to pivot in the second angular direction A2, to an angular position at a distance of, for example, about 6.5 ° from the rest position N, the toothing 34 of the first driving grain 33 engages completely with the toothed ring 19, as shown in Figures 7 and 7a, so that the actuating member 24, bearing on said second toothed grain, shifts laterally along the axis Y ', by sliding its rectangular hole 25 on the part 14. In the course of this movement, the cam surface 27 of the actuating member 24 which is located opposite the second locking pawl 54, bears on the heel 59 of this second pawl of FIG. and locks and pivots said second locking pawl into an unlocked position or its toothing 57 is no longer engaged with the ring gear 19. The first locking pawl 53, meanwhile, remains engaged with the ring gear 19 by the action of the leaf spring 58. In the following pivoting movement of the handle 7 and the actuating member 24 in the second angular direction A2, as shown in Figures 8 and 8a, the second drive grain 33 causes the second frame 9 and the pinion 22 to rotate in the angular direction A2, while the toothing 57 of the first locking pawl 53 simply slides against the ring gear 19, without interfering with the movement of the second 9. The seat 3 is thus driven downwards in the direction B by the movement of the pinion 22. When the user releases its action on the handle 7, said handle and the actuating member 24 return to the seat. rest position N, shown in Figures 5 and 5a, by the action of the spring wire 51. During this return movement, the actuating member 24 resumes a centered position relative to the control shaft 14 , so that the two locking pawls 53, 54 hold immobilized the second frame 9 and the output gear 22. In addition, during this return movement, the toothing 34 of the second drive grain 33 slides against the toothed crown 19, while the first driving grain 32 is always maintained in the erased position by pressing its pin 37 against the central portion 17a of the ramp 17. When the device returns to its rest position, only the first truncated teeth 43 of each drive grains 33, 34 bear each against a tooth flank of the ring gear 19, which prevents premature locking of the return movement and ensures that the actuating member 24 and the handle 7 return accurately in their angular position of initial rest N. The operation of the control mechanism 6 during an actuation in the first angular direction A1 is similar to that described above, mutatis mutandis. Note also that the control mechanism according to the intention can also be used to control any adjustment of a movable part of a seat, other than the height adjustment of the seat 3 already described above. It can in particular be used to adjust the inclination of the backrest 2 of the seat.

Claims (10)

1. Control mechanism for a vehicle seat comprising: - first and second armatures (8, 9) rotatably mounted relative to one another about an axis of rotation (Y), the second armature (9) comprising a ring gear (19) centered on the axis of rotation, - an actuating member (24) pivotally mounted relative to the first armature (8) about the axis of rotation (Y) and being elastically biased towards an angular rest position (N), said actuating member being displaceable, from the rest position (N), in first and second angular sectors (Sl, S2) on either side of said rest position ( N), - and first and second driving grains (32,33) each having a toothing (34) adapted to engage the ring gear (19) of the second armature, each drive gear (32, 33) being pivotally mounted on the actuating member (24) about a pivot axis (35) offset by relative t to the axis of rotation (Y) of the actuating member, the first drive (32) being adapted to engage the ring gear only when the actuating member (24) rotates in the first angular sector (Si) and in a first angular direction (Al), and the second drive (33) being adapted to engage with the ring gear (19) only when the actuating member (24) ) rotates in the second angular sector (S2) and in a second angular direction (A2) opposite the first direction, the toothing (34) of the first drive beam (32) extending in the first angular direction (Al) between first and second ends (41, 42) and the toothing (34) of the second drive (33) extending in the second angular direction (A2) between first and second ends (41, 43), and the teeth (34) first and second drive beads (32,33) each having a series of teeth (43-49) which comprise two converging flanks (44) towards a free end (45, 50), the first and second driving grains (32, 33) being elastically biased towards the ring gear (19) and being arranged so that when the actuating member (29) is in the rest position (N), the first end (41) of the teeth of the first and second driving grains is in the immediate vicinity of the ring gear (19) and the second end (42). teeth of the first and second driving grains are spaced from said ring gear, characterized in that the teeth (34) of the first and second driving grains comprise, at their first end (41), at least one truncated tooth ( 43, 46, 47, 48) whose free end forms a flat portion (45) between the two flanks (44) of said tooth. 2. Control mechanism according to claim 1, wherein the teeth (34) of the first and second drive grains comprise, at their first end (41), a plurality of truncated teeth (43, 46, 47, 48) of which Free end forms a flat portion (45) between the two flanks (44) of said tooth. 3. Control mechanism according to claim 1 or claim 2, wherein each toothing (34) comprises a first truncated tooth (43) located at the first end of said toothing, said first truncated tooth having an outer flank (44), turned away from the second end (42) of the toothing to which the first truncated tooth belongs, the first and second driving grains (32,33) being arranged so that when the actuating member (24) ) is resting position (N), the outer flank (44) of said first truncated tooth is a single point of support of each drive grain (32,33) against the ring gear (19). 4. Control mechanism according to claim 3, wherein said outer flank forms with the flat of said first truncated tooth an angle (a) between 100 and 120 degrees. A control mechanism according to claim 3 or claim 4, wherein each toothing (34) comprises a plurality of additional truncated teeth (46, 47, 48) adjacent to the first truncated tooth (43), said additional truncated teeth having a height of decreasing tooth towards the first truncated tooth (43). 6. Control mechanism according to claim 5, wherein said additional truncated teeth (46, 47, 48) are three in number. 7. Control mechanism according to any one of the preceding claims, wherein the teeth (34) of the first and second drive grains further comprise at least one uncut tooth (49), whose flanks (44) converge towards a free tip end (50). 8. Control mechanism according to any one of the preceding claims, wherein the first armature (8) comprises at least one guide ramp (17) adapted to prevent the first drive wire (32) from coming into contact with the ring gear (19) of the second armature when the actuating member (24) is in the second angular sector (S2) and for preventing the second drive wire (33) from engaging the ring gear (19). ) of the second armature when the actuating member is in the first angular sector (S1). 9. Control mechanism according to any one of the preceding claims, further comprising first and second locking pawls (53,54) which are pivotally mounted on the first armature (8) and which are elastically biased towards a locking position. wherein said first and second locking pawls are engaged with the ring gear (19), the first locking pawl (53) being adapted, when in the locking position, to lock a rotation of the second armature (9) relative to the first armature (8) in the first angular direction (A1) and allow rotation of the second armature in the second angular direction (A2), and the second locking pawl (54) being adapted, when in the locking position, to block a rotation of the second armature (9) relative to the first armature (8) in the second angular direction (A2) and to allow a rotation of the second armature ure in the first angular direction (Al), the actuating member (24) being adapted to move the first locking pawl (53) in an erased position where it does not cooperate with the ring gear (19) when said member actuator is moved in the first angular sector (Si), in the first angular direction (A1), and said actuating member (24) is adapted to move the second locking pawl (54) to an erased position where it does not cooperate with the ring gear (19) when said actuating member is moved in the second angular sector (S2) in the second angular direction (A2). Vehicle seat comprising two parts (3, 5) movable relative to each other in a relative movement controlled by a control mechanism (6) according to any one of the preceding claims.