FR2562183A1 - ARTICULATING AND ARTICULATING ASSEMBLY, IN PARTICULAR FOR A TILTING SEAT OF A MOTOR VEHICLE - Google Patents

Abstract

THE INVENTION CONCERNS CONTINUOUSLY ADJUSTABLE ARTICULATIONS. IT RELATES TO A JOINT IN WHICH THE RELATIVE POSITION OF TWO SUPPORTS 10, 11 IS FIXED BY COOPERATION OF A TOOTH SECTOR 13 AND A TOOTH RATCHET 16. WHEN THE RATCHET 16 HAS COME IN TAKE WITH THE TEETH OF THE TOOTH SECTOR 13 BY MOVING LATERAL BY THE NECESSARY QUANTITY, TWO CAMS 19, 20 COME STOCK IT IN THIS POSITION SO THAT THE BRACKET 10 CAN BE ADJUSTED BOTH QUICKLY AND IN A PRECISE MANNER IN RELATION TO THE BRACKET 11. APPLICATION TO THE SEAT ARTICULATIONS AUTOMOBILES.

Description

The present invention relates to an articulated assembly and a joint,

notanmment for reclining seats

of a motor vehicle.

  In the field of automobile seat angle adjustment devices, a continuously variable adjustment has been obtained by means of a manipulated "jaw" mechanism, in the case of manual adjustment, by rotation of the seat. a cam with a manual button that causes a relative progressive movement of a tooth between the outer and inner gears of the mechanism, for each turn of the handle. The friction of the self-locking elements gives a satisfactory locked state for any position of the continuous adjustment; however, the overall adjustment between the extreme positions is relatively slow compared to reciprocating ratchet and ratchet hinges generally used in the United States of America as described, for example, in United States Patent No. 4,223,947. , in which a cam controlled by a handle releases a pawl of a toothed sector and allows a quick positioning of the seat back, the release of the lever then allowing the cam to lock the pawl in cooperation with the toothed sector. In these hinges, the adjustment positions are progressively limited to a difference of a single tooth, for the positions

sector and ratchet.

  Various techniques have been tried to satisfy the industrial demand for faster and more accurate adjustment with conventional devices which provide a pitch range of a cooperating sector tooth.

  with the ratchet. For example, US patents

  4 223 946 and 4 355 846 describe a linkage

  additional "translation" which is intended to amplify

  proud of the angular movement of the toothed sector -in the

  case of the angular movement of the file so that the

  angle of the backrest is reduced accordingly.

  for the adjustment of a tooth during the cooperation of the pawl and the sector. In another case as described in U.S. Patent No. 4,295,682, the pitch of the teeth is extremely small, thanks to the use of a special clamping mechanism in the cam-controlled mechanism which opposes in a very positive way the separation of the teeth, by

who cooperate.

  Although this has resulted in an increase

  adjustment, a truly continuous variable setting combined with a quick coarse adjustment to the desired position of the backrest.

  never been satisfactorily obtained. Various attempts

  use of friction locks did not allow

  the satisfaction of the test criteria under the action of

  shocks imposed by safety standards, given the cost and space constraints

  the realization of a seat joint.

  The invention relates to a complete solution to this old problem of rapid coarse adjustment and continuous final adjustment in which the blocking resistance of the conventional articulated pawl and toothed self-locking cam mechanism has been retained, with continuous adjustment obtained by fluttering of the pawl over a distance corresponding to a single pitch of the teeth, to a position in total engagement, for a precise adjustment of a conventional tooth sector, the locking of the pawl in such a set position of restraint being then ensured by maneuvering dual cams acting on inclined surfaces of the pawl, a variable path of the relative contact surfaces of the cams allowing a range of position of the pawl corresponding to a tooth, when it takes its initial position of contact. The geometric configuration of the pawl and the cams is such that the length of the cam surfaces is sufficient for the preliminary flutter of a ratchet tooth to be

  possible when it reaches its initial position of cooperation

  with the sector, with an automatic blocking angle of no more than 6 and

the displacement range of the cams.

  In addition to the two articulated cam members which are simultaneously operated by a single handle towards their retracted position, a linkage for positively disengaging the teeth of the sector pawl is intended to retain the pawl in a relative centered position in order to

  the teeth can cooperate initially, the opera-

  being made under the control of a front spring

  that the cams' cooperation with the ratchet takes place.

  The arms extending the respective cams are biased by a tension spring towards the position of cooperation with the pawl enabled by release of the lever. The contact of the cams can be made successively or simultaneously according to the particular initial position of contact of the pawl. In all cases, the housing of the two cams in locked position, all the game being cashed, is obtained without moving the ratchet from

from its initial position of contact.

  The triangular relationship of the pivots of the two cams with the point of engagement with the ratchet teeth and the effective angle of engagement of the cam surfaces are set so that the automatic locking angle is obtained for any compression pressure due to the force exerted by the teeth in one direction and the other. Thus, although the mechanical strength and restraint properties of the sector construction

  teeth and ratchet held by cams are

  the use of ratchet flotation on a single tooth and secondary locking with two cams

  the continuously variable setting combined with a

  rude nemenrit quick of the record, searched for long-

  time by directors of articulatior of inclined seats

fillers.

  Modifications fall within the scope of the

  the floating ratchet for fully cooperating with the sector teeth in any relative angular adjustment position of the seat and back supports which are locked and can not move due to the action of the two cams, each cam having a displacement variable angle automatic blocking that is enough

  for the full range of adjustment variation corresponding to

  at least one tooth, so that the entire adjustment range of the supports is continuously variable. However, it has been found in testing that a preferred embodiment has the greatest durability under severe test conditions.

  without any malfunction.

  In this preferred embodiment, a profile with straight teeth has been used and allows the reduction of the angle of the teeth and the corresponding reduction of the stresses due to the force of separation of the pawl and the toothed sector under the action of the radial component of the forces exerted by the teeth. The rotation of the two

  cams is reversed so that the geometry

  The fact that forces acting on the pawl when a force is applied to the backrest recalls the cam subjected to force to a higher position in which it thus better resists deformation under the action of cyclic forces. The pawl is simplified so that it acts as a tooth slider without a pivot, the hinge arm being eliminated. An original ratchet release and control system permits the use of straight low height teeth having flat ends, and the spring ends exerting torque are intended to bias the cams to a cooperative position in which the ratchet is biased towards the toothed sector and is moved into full cooperation position before the setting of the cams which block

  the ratchet in position. The configuration giving the resistance

  The cams have been optimized for the forces applied to the ratchet teeth so that the resulting forces of the torque applied to the seat on the toothed sector-tooth torque tend to move the pawl onto the axis of the cam pivot subjected to the force. centralized, and that the cams have a fluted profile minimizing the gap

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  in the whole range of cooperation of the ratchet with the cams.

  Other features and advantages of the invention

  tion will become more apparent from the following description,

  with reference to the accompanying drawings in which: Figure 1 is a side elevation of a hinge according to a preferred embodiment of the invention; Figure 2 is a partial side elevation of a variant of the hinge of Figure 1; Figure 3 is a side elevation of a seat hinge, according to a preferred embodiment of the invention; Fig. 4 is a side elevation of a test assembly showing the geometrical configuration of a toothed ratchet and locking cams throughout the ratchet moving range between a neutral position and an end;

  Figure 5 is similar to Figure 4 and represents

  feels the movement of the pawl from a neutral position to the other end; Figure 6 is a detailed elevation of a toothed sector; Figure 7 is a detailed view of the bottom support plate; Figure 8 is a detailed view of the toothed pawl; Figure 9 is a detailed view of the cam used in the test set; and FIG. 10 is an enlarged diagram showing the pawl, the toothed sector and the configuration of the

  forces applied to the cams of the test set.

  FIG. 1 shows an upper support and a lower support 11 of a hinge, which can be connected to the seat and back of a motor vehicle, and which are articulated at 12. A circular sector 13 of the upper support 10 has teeth 14 which cooperate with teeth 15 of a pawl 16 mounted with play on a shaft 17 carried by the support 11 by

  through an elongated slot 18 leaving a displacement

  free cement sufficient for the teeth 15 of the pawl to cooperate with the adjacent teeth of the toothed sector 13 for any relative angular position of the supports and 11, provided that the pawl 16 is approximately centered with respect to the axis 17 of mounting and the slot 18 upon initial contact of the teeth with the teeth

14 of the toothed sector.

  Cams 19 and 20 articulated on the support 11 about axes 21 and 22, have eccentric faces 23 and 24 of cams for cooperating with inclined plates 25 and 26 of the pawl 16. The faces 23 and 24 of cams cover a sufficient circle arc, for example 45, and have a sufficient race for them to come

  in contact with dishes 25 and 26, with a locking angle

  such as 5.50, regardless of the position of cooperation

  ration that can be established for the pawl by the relative position of the support 10, corresponding to a variation of a single tooth, variation allowed by the elongate slot 18. It should be noted that the angular relationship of the faces 23 and 24 of cams, when they reach a position of cooperation with the plates 25 and 26, varies with the movement of the pawl 16 on both sides of the position

  center shown in FIG. 1, a distance corresponding to

  pampering in the not of a tooth being allowed by the slit 18.

  Whatever the intermediate position taken by the pawl 16 when it comes into intimate contact with the toothed sector. 13 before the cams cooperate with the pawl, the locking angle ensured by the contact of the cams ensures the effective rottenness of the pawl 16 and prevents it from moving in one direction or the other under the action of pressure exerted by the toothed sector so that the support 10 is effectively locked relative to the support 11, in any set position of

continuous way.

  It should be noted that a continuously variable adjustment requires full contact of the ratchet teeth and teeth 14 of the toothed sector before either

  cam faces come into contact with the associated surface-

  ratchet 16, the ratchet 16 further having the

  approximately centered when it penetrates

  in the teeth of the toothed sector 13. A suitable sequence

  nabie positioning of the ratchet before contact with

  the cams and preliminary centering of the front ratchet penetrate

  Initial treatment in the teeth is provided by a rod 27 articulated on an axis 28 protruding from the extension 29 of a release handle 30 which is articulated in

  21 on the support. 11. This handle, when moving

  clockwise, and by contact with the face 31 of the extension 29 with pins 32 and 33 protruding from the cams 19 and 20, is intended to move the cams of the pawl 16, under the action of the

  force of a tension spring 34 placed between them

  35 and 36 of the cam arms 19 and 20. The movement

  linear cementing of the rod 27 under the control of the handle 30 towards the limit of the slot 37 relative to the axis 38 which protrudes from the face of the pawl 16 in the slot 37 ensures a positive separation of the pawl and the toothed sector despite the restoring force of the tension spring 39 fixed to a projection 40 of the lower face of the support 11 and connected at its other end to an extension of the axis 38 of the pawl 16 protruding through a triangular slot 41 of the support 11 This contact of the axis 38 with the end of the slot 37, during the disengagement, takes place after the release of the two cam faces 25 and 26 and ensures the centering of the pawl with respect to the slot 18 by cooperation of the 38 with a precise end 42 of the slot 41. The ends of the movement of the cams are indicated in the case of

  arm 19 by circular arcs formed on 15 and 30 res-

  on each side of a neutral axis 43 corres-

  laying at the neutral position of the pawl 16 as shown.

  During the return path in the handle 30 in the opposite direction of clockwise, the same linkage, under the action of the force of the spring 39 acting on the axis 38, causes the cooperation of the teeth 15 of the pawl 16 with the teeth 14 of the sector 13 before the return of the cam faces 23 and 24 in contact with the plates 25 and 26, this contact being effected without moving the pawl from its previous position of total cooperation with the teeth of the sector, whatever the continuously adjustable position of the support 10 to

  moment of initial contact of the pawl.

  FIG. 1 represents a suitable form of teeth, having a pitch corresponding to 2.5, the teeth being well pointed on the pawl and on the sector and being

  manufactured by conventional broaching, ensuring

  preventing the relative movement of the pawl teeth and the toothed sector, so that the pawl can not be retained until full cooperation with the

  sector toothed regardless of the position of it.

  Another method of manufacturing by fine stamping teeth of the toothed sector and the ratchet is not suitable for sharp teeth since it is mandatory

  in the matrices a small radius at the tips.

  Such a radius increases the possibilities of relative contact of the ratchet teeth and the toothed sector which could

  to prevent their proper cooperation.

  FIG. 2 represents a variant that allows a positive lateral displacement of the pawl with respect to a position of cooperation of the tips of the teeth so that the need for the realization of sharp teeth is less demanding, so that the stamping can be used to the manufacture of a joint according to the invention. In the case where the tips of the teeth cooperate and prevent engagement, the lateral displacement of the pawl is provided by a small lug 50 which protrudes from the ratchet face and which is in the path of the end 51 of a ratchet. extension 52 of an arm, the positions reached at the moment of imminent cooperation of the ratchet teeth and the sector being relatively close when returning the pawl and the operating handle. When the teeth penetrate on one side of the teeth of the toothed sector sufficiently so that they are well engaged, an extension 51 passes under the lug without being in contact with it during the return of the cams to their position; however, when the full cooperation is interrupted by contact of the aligned tooth tips, the end 51 comes into contact with the lug 50 and moves the pawl laterally to the left sufficiently to ensure full cooperation of the teeth before the

camming cooperation 19 and 20.

  As the ratchet and extension of the handle always reach the same relative positions at the time of the imminent cooperation of the teeth, the lug always has a position determined with respect to the point

  51 and can therefore fulfill its function if necessary.

  Figure 4 shows positional elements

  of the test assembly comprising a toothed sector 53 having teeth 54 centered on a pivot placed between lower support plates 56 placed on either side (one being suppressed for the sake of clarity), a sliding pawl 57 provided with teeth, double cams 58 articulated at 59 between the lower supports 56. In FIG. 4, the cams 58 and the pawl 57 are represented in solid lines in the neutral position and in broken lines when the pawl 57 is moved to one end while, in Figure 5, the pawl 57 and the cams 58 are shown in solid lines while the dashed lines represent the pawl moved to the other end. The total displacement range of the pawl 57 is of the order of 3 so that it allows a continuous adjustment of the sector 53 with a spacing of

  2.5 teeth. The ratchet 57 has a circular arc which

  takes the curvature in the contact zone with the cams

  58, on a very limited band of the entire adjustment range.

  The upward portion of the cam, about 120, corresponding to an effective coefficient of friction that is not less than 0.07 and is in the form of

  a curve with a substantially constant locking angle

  both with respect to an axis passing through the pivot of the cam and the point of contact of the pawl. It should be noted that this upward portion of the cam is oriented so that it gives a minimum dimension to the center of the pivot at the lower and upper ends at the upper end so that any tendency of the pawl 57 to deviate from the teeth of the sector tends to roll one or the other cam towards a point of contact higher and not lower, as in the case of the upward part of the cams used in the embodiments of the figures

  1 and 2. It can be seen during the test

  The camshaft of FIGS. 4 and 5 is more effectively opposed to any tendency to deform the cam surface as a result of repeated cycles of use.

  under significant forces applied to records.

  The relative convex curves of the cam and pawl in the contact area minimize the deviation of the optimal geometric configuration of the force vectors, as described hereinafter with reference

in Figure 10.

  The test elements shown in FIGS. 4 to 9 have been made according to the criteria of a

  backrest adjusting device having a continuous range.

  In an example of components that satisfy cyclic torque application tests, Figures 6 to 9 indicate dimensions in millimeters

  give primordial geometric relations satisfying

  cient. In addition, the supports 56 are made of AISI 1018 steel of 4.5 mm thick, the toothed sector was formed in steel SAE 1020, with a thickness of 4.5 mm, after a heat treatment KN 086240 and the ratchet is made of 4 mm thick AISI 4130 steel, hardened and annealed to a Rockwell C38-48 hardness, the cams being made of 4 mm thick AISI 4130 steel, tempered and annealed at a

Rockwell C38-45 hardness.

  As shown in FIG. 10, the arrangement of the forces ensuring the positioning of the cam pivots can be understood from the following analysis. A number

  of teeth is determined according to the

  shear stresses due to the corresponding maximum load

  to the final torque, with a suitable number of teeth ensuring the stability of the pawl, determined in the case considered to be equal to ten straight teeth, as shown, having a pressure angle of 14 45 'and a

  spacing of 2.5. the determination of the center of applica-

  tion of the force 60 to the tooth and the summation of the force vectors 61 and 62 due to the tangential torque applied to the center of force of the tooth and the radial component for the pressure angle of 14 45 'give a resulting straight line 63 passing through. very close to the center of curvature 64 of the arc

  circle of the ratchet at its point of contact.

  The optimal center of curvature of the cam for the neutralization of a torque applied to the cam is

  on an extension of line 63 and an additional angle

  65 of 2 is added so that it prevents any tendency to separate the pawl due to the summation of forces to individual teeth, the axis thus passing through a center of curvature of the cam disposed at 66 and passing through the center curvature of the ratchet. In addition to this force, it is noted that any tendency of the ratchet to deviate tends to cause a rolling of the cam towards a position corresponding to a higher part, so that this behavior also opposes the movement of the ratchet from the position of contact with the teeth of the

toothed sector.

  Given the curvature of the pawl and the cam at the point of contact, a single tooth displacement of 2.5 of the pawl over the entire range of co-operating position, allowing continuous adjustment, gives a very narrow contact strip. on the pawl, such as points 67, minimizing any deviation from the optimal geometric configuration with respect to

  to the axis of the cam in the entire adjustment range.

  Tests have shown that, with the dimensions and configuration indicated above, the pawl does not tend to move and the cam does not tend to deform under the action of maximum torque cyclic forces, even when a cam to which a force

  is not applied is not in contact.

  As shown in FIG. 3, the ratchet 57a and cam 58a variant is intended for movement over a smaller arc, and has a striking release mechanism. The pawl 57a and the cams 58a are shown in the neutral position. Two operating rods 67 and a shock-actuated connecting rod 68 are displaced at the ends of respective slots-shaped openings by an axle 69 mounted at the end of a manual release lever 70 hinged at 71 and movable towards a the position indicated by the reference 72. It ensures successively the release of the cams 58a and the operation of the striking member 73 articulated at 59 so that the pawl moves against the projection formed by stamping, the pawl 57a then having to move towards the left by spreading the teeth, in the limit of the cavity 76 which is housed against the

projection 75.

  The downward movement of the connecting rod 68 which is in contact with the lug 77 exceeds the torque exerted by the spring 78 which pushes the lug 79 of the connecting rod 67 in the direction of engagement of the cams and pushes the reaction member back. Counterclockwise stroke, this descent also exceeding the force exerted by the spring 80 which pushes the pin 81 in the direction of the cams cooperation and

  the pin of the pawl in the direction of cooperation of the teeth.

  Thus, when moving the manual lever 70 of its

  position 72, the pawl pin is raised by the end

  mite of the spring 80 to the contact position of the toothed sector teeth and, after abutment of the flat ends of the teeth of the pawl and the toothed sector, the inclined surfaces 82 of the member 73 cause a movement of the pawl 57a to the right, until the teeth are properly engaged, the pawl 57a then being in the set position before the cams 58a return to their position

respective contact.

  Although the cams are shown in FIGS. 4, 5 and 9 with a rising portion covering, taking into account a coefficient of friction of 0.07

  given by conventional lubricating greases, lubricants

  special binders such as manufactured by Monsanto Chemical Compaiy under the trademark "Santotrac" give higher coefficients of friction of the order of 0.12 allowing a reduction of the arc of the cams to about 70 and giving the same ascending part only in Figures 4 and 5. This shorter arc is used with

  the release mechanism of Figure 3 for the

  of the lug 79 of the connecting rod 67 between the engagement limits with the cam indicated at 84 and the lug 81 between the limits 85. The additional displacement

  of the connecting rod 67, for example so that the ergot 79 reaches

  at another end 86 and allows the operation of the striking member 73 by the connecting rod 68. is made possible by displacement of the lug 69 of a position 87, at the lower part of the position of the slot 88,

  at the limit of the release stroke 72.

  The inclined surface 83 is long enough to allow the initial entry of the teeth without locking the ends of the pawl teeth and the toothed sector, but if this contact is made, the movement of the pawl 57a to the right is ensured by the ramp 83 until the teeth are engaged. The slot 82 of the plate 56a limits the total displacement of the pawl 57a to about 3, sufficient for a spacing of the teeth of 2.5, by lateral displacement.

limited ratchet lug.

id

  The foregoing description relates to

  Particularly useful for positively securing a toothed ratchet for continuously variable adjustment on an articulated toothed sector. This construction achieves particularly well the joints of the reclining seats and allows a quick release and adjustment of the backrest to the exact desired location, with a positive locking, giving the advantages of a great robustness, peculiar to the system having ratchets and toothed areas,

  but without the disadvantage of a progressive adjustment% limited.

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Claims (34)

  1. Articulated assembly of elements, characterized in that it comprises a continuously adjustable device   intended to block the connected elements in ana-   Laire, comprising a toothed device (14) formed on one of the elements (13) and cooperating with a toothed device (15) of the other element (16), a mounting device allowing the total separation of the toothed devices during the adjusting the relative angular position, the mounting device comprising a device for the complete engagement of the toothed devices so that the elements can be adjusted angularly continuously, and a cam device (19, 20) for entering into cooperation after the toothed devices have been engaged and intended to lock the respective toothed device so that it can not move angularly. 2. An assembly according to claim 1, characterized in that it comprises double cam surfaces (23, 24)   which can be arranged individually and which   to the cam device (19, 20), these surfaces being intended to cooperate individually with angularly associated surfaces of one of the toothed devices (15) so that they oppose the relative movement of the elements under the action of the forces exerted by the teeth, angularly.   3. An assembly according to claim 2, characterized in that each of the surfaces (23, 24) of cams has a reaction mounting device mounted on one of the elements and allowing a cooperation independent of the surfaces. co-operating inclines.   An assembly according to claim 3, characterized in that each of the cam surfaces (23,24) has a pivoting mounting device and an angle of engagement of the friction locking cam surfaces with respect to the pivotal mounting in any the range of cooperation cams.   5. An assembly according to claim 1, characterized in that the mounting device for a tooth engagement comprises a limited free movement connection sufficient for movement over a distance corresponding to the pitch of a single tooth. 6. The assembly of claim 5, characterized in that one of the toothed devices comprises a toothed pawl (16) with the displacement mounting device free limited.   7. An assembly according to claim 6, characterized in that it comprises a device for centering the pawl (16) relative to the limited free displacement device,   during the start of tooth engagement.   8. An assembly according to claim 1, characterized in that one of the elements is a toothed sector (14) having a center of curvature coinciding with the pivoting connection. 9. An assembly according to claim 8, characterized in that one of the toothed devices is a toothed pawl (16) having a limited free displacement connection with the other of the elements, and intended to cooperate with the toothed sector (13). , the pawl being locked in the setting position by the cam devices.   10. The assembly of claim 1, characterized in that the articulated elements comprise supports (10, 11) of a joint.   11. The assembly of claim 1, characterized in that the articulated elements are the supports (10, 11) of a joint intended to be used for the adjustable backrest of a seat.   12. An assembly according to claim 11, characterized   risé in that it comprises a handle 30, manually controlled-   and to operate the cams (19, 20) towards the release position during adjustment, and an elastic device (34) for returning the cams into position.   of cooperation when the handle is released.   13. An assembly according to claim 12, characterized in that it comprises individually articulated cams.   (19, 20) controlled by a single handle.   14. An assembly according to claim 9, characterized   in that it comprises an elastic linkage (27) com-   driven by a handle and intended to disengage the pawl after the cams (19, 20) have been released and to put the pawl in the cooperation position before the delivery in cooperation with the cams.   15. The assembly of claim 9, characterized in that it comprises a pawl centering device so that it returns to the cooperation position in any set position of the toothed sector within the limits of the limited free movement device of the connection. ratchet.   16. The assembly of claim 1, characterized in that it comprises a device for ensuring   relative lateral displacement of the teeth in the event of   preliminary treatment of the tips of the teeth, preventing complete engagement of the teeth.   17. The assembly of claim 9, characterized in that it comprises a device for causing a lateral displacement of the pawl when the teeth have their points aligned initially and prevent their engagement.   18. The assembly of claim 15, characterized in that it comprises a device for moving the pawl laterally from its centered position, when the tips of the teeth are aligned and prevent   the engagement, in the set position.   19. An assembly according to claim 18, characterized   in that said device for moving the pawl comprises a projection of the pawl intended to cooperate with an extension of the handle when the cooperation of the teeth of the pawl and the toothed sector is interrupted in the set position.   20. An assembly according to claim 19, characterized in that said protrusion and said extension have sharp corners intended to cooperate after new interrupted cooperation of the ratchet teeth and the toothed sector in the set position, the backs of the sharp corners forming a thin line. demarcation between the positions of cooperation and bypass in relation to the respective corner.   21. An assembly according to claim 15, characterized   in that the ratchet centering device comprises a lug (82) protruding into an opening (83) having a centering wedge, and a device for moving the lug in the centering wedge after disengagement of the sector.   22. An assembly according to claim 12, characterized   characterized in that it comprises two cams (19, 20) articulated individually, and a pawl for cooperating with the cams, the elastic device for biasing the cams to a contact position comprising an individual articulated mounting for each of the cams, with an individual torsion spring (78, 80) recalling each cam towards its contact position.   23. The assembly of claim 7, characterized in that the limited free displacement mounting device and the centering device comprise a lug protruding into a mounting aperture, and an elastic device placed in the opening and moving the lug so the ratchet is pushed back to a central position cooperation.   24. An assembly according to claim 8, characterized   in that the toothed sector is convex, and the other   toothed tooth is a ratchet having a concave arc equipped with teeth.   25. An assembly according to claim 2, characterized   rised in that the inclined surfaces are the surfaces   external ratchet with teeth.   26. An assembly according to claim 2, characterized   in that the cam surfaces comprise a surface of each of the individual cams articulated on remote pivots. 27. Articulation adjustable for seat back, comprising articulated supports of a seat and a backrest, a toothed sector (13) carried by one of the supports, a toothed pawl (16) for holding the sector in position adjusted relative to the other of the supports, and a device for temporary positioning of the pawl in the fixed and set engagement position relative to the sector, characterized in that it comprises a device for mounting the pawl (16) with sufficient freedom 0 to allow a movement of at least one tooth relative to the sector, inclined surfaces formed on the pawl, two cams (19, 20) separately mounted in articulated form on the other support, the cams having   surfaces (23, 24) which can be positioned indi-   and which can cooperate individually with the inclined surfaces to oppose the movement of the pawl from any position of initial engagement with the toothed sector, with a support angle which can be continuously adjusted, a device ( 27) of successive displacement of the pawl in initial cooperation position with the toothed sector in any given set position of the supports and then displacement of the cams in the position of cooperation with the ratchet.   28. Articulation according to claim 27, characterized in that the teeth of the sector. (13) and the ratchet (16) has a profile whose upper part is flat. 29. Articulation according to claim 28, characterized in that the profiles of the teeth give   a pressure angle of the other of 14.75.   30. Articulation according to claim 29, characterized in that the spacing of the teeth corresponds at an angle of about 2.5.   31. Articulation according to claim 30, characterized in that the contact of the cam and the pawl is performed along an axis corresponding to the resultant tangential force applied to the teeth and the radial force due to the pressure angle of the teeth, at   center of cumulative force applied to the ratchet teeth.   32. Articulation according to claim 31, characterized in that the contact surfaces of the ratchet   (16) and cams (19, 20) have a convex curvature.   33. Articulation according to claim 32, characterized in that it comprises a pawl (16) of simple sliding type having convex surfaces of contact with the cams, on the axis of application of force under the action of tangential forces due to the torque and given the pressure angles of the teeth ensuring the application of a displacement force inclined in one way or the other.   34. Articulation according to claim 33, characterized in that it comprises a pawl control member (68) articulated on the pivot axis of one of the cams, a pawl control pin (82) protruding from the ratchet surface, contact surfaces formed on the control member of the clip being for moving   this one to the position of cooperation and out of that   here, an elastic device pushing the element of com-   driving the pawl towards its position of cooperation with the toothed sector and pushing the cams into a position of cooperation ensuring the positioning of the pawl, and a manual device (70) for successively disengaging the cams and operating the control element, in   the meaning of the release of the ratchet.