CA2033049C

CA2033049C - Seat for a vehicle provided with a safety belt with fixation points embarked on the armature of the seat

Info

Publication number: CA2033049C
Application number: CA002033049A
Authority: CA
Inventors: Michel Hallet; Frederic Degrenne
Original assignee: Bertrand Faure Automobile SA
Current assignee: Faurecia Sieges dAutomobile SAS
Priority date: 1989-12-26
Filing date: 1990-12-21
Publication date: 1994-07-05
Anticipated expiration: 2010-12-21
Also published as: CA2033049A1; BR9006568A; EP0435740B1; ES2055381T3; FR2656263A1; IE904671A1; ZA9010318B; FR2656263B1; ATE106047T1; MX173168B; PT96366A; DE69009162T2; DE69009162D1; AU642943B2; AU6846690A; EP0435740A1; JPH04135949A

Abstract

ABSTRACT
One end of the strap forming the safety belt is rigidly connected to a rear lower portion of the armature of the seating portion of the seat by a blockage mechanism. A shoulder keeper situated frontwardly with respect to the upper portion of the front face of the seat back provides for a sliding and guiding of a run of the safety belt passing above the passenger shoulder. An other end of the run of the safety belt is secured to an iron fitting fixed with one of the side flanges of the seating portion armature and forming a second fixation point. A keeper cooperating with a lock forms a third lower fixation point of the safety belt and is connected to the side flange opposite the second fixation point on the armature of the seating portion of the seat. The two side flanges receiving the fixed and mobile portions of the back seat inclination setting mechanisms with respect to the seating portion of the seat are placed in a position such that a pivoting point of these mechanisms is in a position which is in front of a normal pivoting point of these mechanisms by a certain distance.

Description

~ ~ \` 20~3~

FIELD OF THE INV~TION -~
The present inve:ntion relates to a seat for a vehlcle provided with a safety belt wlth fixation points embarked on the armature of the seat.
BACKGROUND OF THE IN~ENTION
In the present vehicles, each seat is provided with a safety belt which is of the type known under the name of "three polnt type" safety belt, meaning that the :~ :
: fixatlon of the strap formlng the belt ls made, by one ~`
of its ends, on an automatic winder rigidly connected to ~ the vehicle body and formlng the first fixation polnt, ;~ ~ while the second end of the belt is fixed by means of a lock placed either on the right side or on the left side of the seat, according to whether lt ls a left side seat ~, or a right side seat 80 to form the second fixation point ; the intermediste or third fixatlon point, that 18 the point situated between the automatlc winder and : the lock, is normally also fixed to the vehicle body, 90 that the strap~forming the belt is wound on the ; ~ ~
20 automatlc wlnder and extends through a kseper situsted ~:
on the car body on a point thereof substsntlally at height of the passenger shoulder and ls flx~ed by lt other end as hereabove indlcated on the~lower portlon of .;~`
~; the vehlcle, thst ls on the car body as such, or on the ; 25 frame of the seating portlon of tbe seat.

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~.'.3' 203~Q~9 "., ~ .

However, these known safety belts have a i~ disadvantage of requlring a lengthy lnstallatlon, and ;~ are therefore costly to mount and of a large volume (see ln particular DE-A-3 429 426 and DE-A-3 613 830).
; :
Attempts have been made to remedy these ~, disadvantages by providing a so-called "three embar~ed ~.~
~: polnts" safety belt, meanlng that the three flxatlon points of the safety belt are flxed on the frame of the ~:~ seating portion and of the seat back of the seat, but lO one is then confronted with a ma~or disadvantage when, as,it 1s now the case, the lnclinatlon of the seat back can be set at wlll by the passenger. Actually, in this , :~ case, the artlculation mechanlsm situated between the seating portion and the seat back are su~ected to very lS large efforts which can go as far as breaking these ~ mechanisms if an accident occurs.
: Indeed, the run of the strap passlng over the f ~ shoulder and breast of the passenger in order to Jolnt , ~ the ventral run of the strap applies, malnly whèn there 20 is sn uccident, very hlgh efforts on the seat back which : c~n exceed the maxl~um admiss1ble effort value for the:
, articulatlon mechanlsmo.
~ In addltio~n to th1s ma~or disadvantage, i;t has~
`~ appeared that the presently~known winders with automatic ~: - 25 blockage were also not able to support ~uch:effortu aDd:
that therefore, at~the ~oment of an lmpact, the`oufety ~ ;l 20330'~9 ,.

r~ ~ belt does not fulflll absolutely lts protectlon role, which aggravates the passenger corporal hazards.
OBJECT AND SUMMARY OF THE TNVENTION
Therefore, an ob~ect of the present inventlon is to provide a vehicle seat lncludlng the seat lncllnation settlng mechanisms with a mounting of safety belt wlth three points fixed to tbe seat armature (seating portion of the seat and seat back of the seat) but by using most often an automatic winder and employlng means protectlng 10 the user ln all cases wlthout a risk of a~too rapld destruction of the articulation mechanisms and of the automatic wlnder. ;
According to the lnvention, the vehicle seat provided wlth a safety belt with flxation polnts 15 embarked on the seat armature is characterized in that :
one o the ends of the ~trap forming the ~afety belt ls rlgidly connected to the rear lower portlon of t-he ~ ;
armature of the seat seating portlon by a blockage ` mechanism, then a shoulder keeper sltuated fronwardly~ -~

20 with re8pect to the upper portion of the~front face of the~seat back provldes for~a sliding and guldlng of n run of the safety belt passlng above the pa6senger shoulder, an other end of the run of the ~a~ety belt being flxed to an iron fitting fl~ed with one of the 25 81de flange6 of the senti~ng~portion armnture~and~fornlng the second flxation point, then a keeper, cooperatlng ~ ; 3 æo33~ls with a lock formlng the thlrd lower fixation point of the safety belt, being rigidly connected to the side ~: flange opposite the second fixation point on the ~: armature of the seating portlon of the seat while the two side flanges receiving the fixed and mobile portion~
of the seat back inclination settin~ mechanism with respect to the seating portlon of the seat are placed ln : a posltlon such that a pivoting point of the~e mechanlsms 18 ln a position whlch is in front of a :~ 10 normal plvotlng point of these mechanisms by a distance sufflclent for substantially cancelling the efforts of ~ the safety belt on these articulatlon mechanlsms.

:~ Varlous other feature of the lnventlon wlll .~:
i; become apparent from the followlng detalled description.
: ~: :
:~ 15 BRIEF DESCRIPTION OF THE DRAWINGS
, :
Embodlments of the obJect of the inventlon are . ~ shown, by way of non limiting examples, ln the ~; accompanylng drawings, wherein :
~: Flg. 1 is~a perspectlve view of a seat provlded :~
:20 with a`&aety belt of a "three embarked pQlnts"~type on the seat armature, with the safety belt ln lts:rest ;~ ~ pos1tion ;
i8.~ 2 18 ~a vlew corresponding to Fig. .1, with the safety belt in a worhlng position ;~ ~ :
~ 25 ~ig. 3 18 a rear~pèrsp~ctive vlew of~the seat~
;~ wlthout 1ts garni~hlng~:~show1ne the ~rmature and the~

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r`i 20330~9 . .
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lron flttlngs lntended for fixation of the safety belt wlth three embarked polnts ;
Flg. 4 is a front view correspondlng to Flg. 3 ;
Figs. 5 and 5a are enlarged views showlng a :~
portion of the members of the safety belt according to the invention ;
Fig. 6 i8 an enlarged elevation view showlng a detail of the safety belt passing on top of the seat back ;
Fig. 7 is a front perspective view showing the seat armature provided with the safety belt ; :
~ Fig. 8 i8 an enlarged view of a detail shown in : slde elevatlon, illustratiDg an alternatlve embodiment of a portion of the safety belt ;
Fig. 9 ls a side elevatlon view of a detall of `;`
another embodlment of the safety belt ; ~;
Fig. 10 is a side elevation vlew of the mechanlsm of Fig. 9 in the blockage positlon ;~ `~
Flg. 11 is a slde elevation view of a:third embodlment of a portlon~of the safety belt ;:~
:~ Fig.~12 is~a~slde élevation vlew correspoDding to Flg. }I showlDg the mechanlsm ln another posltlon ; ~`~
~ : Fig. 13 shows a~side elevation vlew of ; ~ modification of one of th~e members of the Beat uslng a ~ :
: 25 safety belt with three embe~rked polnts : :~
:

il -- 20330~

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Fig. 14 ls a side elevatlon view correspondlng to Flg. 13 of the mechanlsm of thls figure in an other ,.1, posltlon ;
~ Flg. 15 is a slde elevation view of a variant of 1~ ~ 5 Fig. 13 ;
Flg. 16 shows the devlce of Fig. 15 in a slde elevation vlew ln another positlon.
DISCLOSURE OF P~EFERRED EMBODIMENTS
Referring now to drawings, Fig. 1 shows a , :~
lO vehlcle seat, more particularly for an automobile, but whlch can also be used in other vehlcles, notably ln i,~ ~ aircrafts.
i~ ~ The seating portlon 1 of the seat lncludes, on ,, ~ its armature 2, rearwardly, side flanges 3 the upper ' 15 portion 3a of which i9 provided for receivin~ the fixed element of the rotation mechanism enablin~ the seat back 4 of the seat in conslderation to be moved ~o as to put the seat back 4 ln a desired positlon for uslng the seat~ The controI of thls rotatlon device can be elther ``
20 manual~, or motorized as it is the case ln the maJorlty ;~
of~odern vehicles.
,Of course, the armature 2 of the seatlng portion of the ~eat 18 also mounted on devices enabling the longlt~udinal displacement of the seat, and also the 25 variable inclination of the 6eating portion by uslng a ralslng device, known per~se.

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The seat can also comprlse in some cases, in the upper portion of the seat back, a head-rest whlch i9 not shown in the present case.
Likewise, the upholstery of the 3eat, meanlng ~ 5 that of the seating portion as well as of the seat back, ;~ can be made at wlll so a~ to provide as much comfort as po~sible for the passenger.
Flg. 3 shows a rear perspective view of the armature 2 of the seating portlon 1 whlch i8 made of a ~; 10 tube convenlently shaped~, and the end8 2a, 2b of whlch tubRs are fixed by any convenient means on identical ~-~ :: supports 5: made each of a base 6 and two parallel ;~ flange 7, 8. The latter are nor~ally covered when the ;~
seat ls finished by the covering flanges 3. The bases 6 ~:~
and the flanges 7, 8 are made of a steel sheet 80 as to make rlgid the lower rear portlon of the armature of the seating portion. Moreover, this rear portion of the ` armature of the seating portlon is reinforced by a~;tube : : 9 the ends 9a, 9b of which are flxed by any convenient means ~n~the bases 6.~
It~should a1~so;~be notlced that the outer:flange 8 of each support 5:includes an upper e2tenslon 10 on ~: : which sre fixed the~::fixed flange of the seat back "`~ ortlculatlon mechan1s-~and the mobile f1snge~;o thl~
: 25 artlculation device, the~latter belng rlgldly connected :: to the armsture 12 of;~the seat back 4. :~

: ~ : : ~::

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~ ^ 2~330~9 The armature 12 of the seat back 4 ls made o~
.. ~ two frames 13, 14 of a trapezoidal shape whlch is tapering upwardly, and are connected at their top by a : channel-shaped frame 15 making rigid the upper portion of the armature 12 of the seat back 4.
;~: ~ Moreover, the base of the frames 13 and 14 as .,, well as the rear portlon of the upper extenslons 10 are 1' : ~:
~;~ ;~ provided with gussets 16, 17 for settlng in position a hollow traneverse bar (a tube) 18, the purpose of which will be explained hereafter.
, Flnally, there is provided on the front portion ~` ~ of the right support 5 ln the present case, a yoke 20 ,~ ~ intended for supporting the lock of the safety belt.
Lastly, the upper channel-shaped frame 15 of the lS armature 12 of the seat back 4 18 provlded with an iron fitting fixed to the upper left-hand side portion of the frame (see ~ig. 3) snd through which extends the upper ;~ run of the safety belt. (In this case, lt is a left-hand .
side eeat, the lron fittlng~21 belng~on the rlght~for a -rlght~sld~e;seat). The keeper 21 is sltuated ln~front of the fron;t face o~f~th~e aeat back 4 (see Flg.~6,~llne ~-Z~
AB shown in Flg. 2, the safety belt 30 i~ held ~
at it~ lower free;end~30a by. a keeper~31~which~is ;rigldly connected by a bolt or rivet 32 to the~support 5 corrying the flangea 7~and 8.

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~`~` 203~9 9i;~
In some cases, the flange 8 is made of two plates 8, 8a (see Fig. 5) rlgldly connected together so as to enable a setting ln position, for the other end 30b of the safety belt 30, of a fixatlon point 34 made :~
5 by the superimposition of transverse bars retained :
between the supports 5, these fixation plates being .
connected by a bolt and nut arrangement 35, but which could also be connected together by any other suitable means. :
: lO As shown in Fig. 5, the lower end 30b of the bel't 30 passes along a transverse tube 118 connecting ` ~ the flange 8 together, then around the tube 18 flxed on ~ :
the gussets 16, then returns around a tube 218 :
connecting the flanges 8 tr:ansversely together, and finally, extending behind the seat back 4 of the seat, 811de9 through the upper lron fitting 21 formlng a ::
keeper, the other end 30a of this belt belng fixed on the ~-keeper 31 as hereabove explained ~Flg. 7). :
~ It should be~noted that, if we assume tha;t the ;~
.~ 20~ tractlon effort applled on the strap 130a ls equal to 1, ` ~ ~due~to the success1ve passage on the;:po1nts 21~8~, 18~and 118, the force exerjted accordlng to F3 is equal to 2.
Therefore, the force F3~has a tendency to rotate the seat back armature~ 12 rearwardly accordin~ to arrow F4.
: 25 The effect of the resu1tant force F3 i8 to cancel or~ :~

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~i 2 ~ 3 3 ~e ~3 mlnlmize the rotation torque along F5 exerted on the ~: artlculation point.

~ The run, forming the safety belt 30, comprises a D"'7 keeper 38 which is mounted freely on it and ends into a cruciform catch 37 lntended for penetrating, as it is . ~ u~ual, inside a lock 39 for the fixation of the safety ~: ~ belt, s1nce the lock 39 i8 rigidly connected to the yoke x ~ 20 (see Flgs. 1, 2 and 7).
~, ~
;~ By referrlng to Figs. 2 and 7, it i8 clear that lO~the safety belt 30 ls subdivided lnto three successlve :~ runs, i.e, a rear run 130a, a front breast run 130b and a ventraI run 130c due to the lower flxation lron `: ~ flttlng 34 of the upper keeper on the back 21 of the ; catch 37 cooperating wlth the lock 39 and finally to the .~
15 fixatlon point witb keeper 31. . .
In some cases, the rear flxation polnt 34 i8 , ~'.,.
~; replaced (see Flg. Sa) by an automatlc wlnder 43, known :,.
~: per se, and on which 18 normally wound the ma~or portlon of~the safety belt 30:vheD the safety belt i9 not ~ .
~ 20 ~operatlng.
`~ The hereabove~construction~lea:ds~1mmed1ately to : ~,~
, two remarks.
; Due to the:;fact that the artieulation mechanisms which allow the angular displacement of the ~eat back~4 25~ of the seat are dlsplaced frontwardly of the~:seatiD~
: ~ portio~ (point lOj;si~nce they are fixed on the upper: .:`

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~ 2~33~9 extensions of the supports 5 substantlally in their medlan zone, there is therefore obtalned a decentering of the seat back armature 12 and of the seat back 4 wlth respect to the seatlng portion 1 (see Flg. 4 where the line x-x represents the abscissa line and y-y the ordlnate llne), the point B belng the normal articulation point and the polnt A being the real plvotment polnt of the rotation mechanism which is situated at about 50mm from the point B ln the present ~; ;
case. Moreover, the keeper 21 being placed in the upper portion of the seat back 4 but on its front face, the ;~
effort of the strap maklng the safety belt 30 i8 ' therefore transferred above the passenger shoulder and in front wlth respect to the seat back 4, the result being that the torque exerted on the articulation mechanism i9 very small.
Actually (see Fig. 5), the components of the rear runs 130d and 130c on the tubes 118, 18, 218 are such that an antagonist force i5 created and provides a torque which reduces considerably the torque exerted on the seat back articulation mechanisms.
For summarizlng, the position in front of the ;~
æeat back articulation mechanisms 12, the position of the keeper 21 rlgidly conneeted to the channel-shaped fIange 15 in fro~lt and above the passenger sboulder ~ointed to .
the lower rigid fixatlon of tbe run 130a eitber o~n 203~

flxed polnt or on an automatic wlnder, avoid any damaglng torque on the articulations, which enables making a safety belt with three embarked polnts.
In Flg. 8, the lower run 130a of the belt shows S another embodlment of the lower flxed point of the strap having practically the same feature as hereabove as ~ ~ :
shown in Fig. 5. Actually, the throughgoing tubes 118 : and 218~are rlgidly conneeted to the armature of the .`
seating portion of the seat, and only the return tube 18 0 i8 flxed at the bottom of the seat back, thereby :
limiting the efforts applled to the seat bae~ of the :.
seat .
In some cases (Fig. .9), lt is posslble to fix ln .,`.` .
addltion to the throughgolng tube 18 mounted on the seat .:.;- i:
15 back armature, throughgolng tubes 318, 418 mounted on ~`... ~.. ~
the armature o~ the seat1ng portion, and the : throughgoing tube 18 ln then s1ldably mounted ln wlndows i : 80 formed on elther side of the seat back 4 in the ;..... ` ~
gussets 16, 17. A res11ient element 81 tends to brlng ... ;ij.:.:
2~ the throughgoing tube 18 back to:the position which~ls .. :. .~.. -`"
most remote from the throughgoing tubes 318,~418. As ~ -:~::.' shown in Flg. 9, the throughgo~ing tube 18 ls s1tuated ln ~.. .~::.:
a slanting.plane parallel to the plane deflned:by the ~: throughgo1Dg:tubes 318, 418,::and~the tube 18 can effect .
a move~ent (dlrection~of the arrow Fl, Pig. 10), in a plane perpendlcular to the two hereabove de~ined~planes.

~ . ~

2~33~

In the event of an impact (see Fig 10), the tube 18 slldes in the windows 80 of the gussets 16, 17 i~ dlrectlon of the arrow Fl (Flg 10) and then comes to bear against the throughgoing tubes 318, 418 by firmly blocklng the lower run 130a of the safety belt, thereby causing an antagonistic torque cancellin~, any efforts ; applied on the articulation mechanism 10 mounted on the seat back armature 12 In Fig 11, there i9 provlded in addltion to the 10 throughgoing tubes 318, 418 a throughgoing abutment 518 sliding in windows 180 formed in the gusset 16, 17 The abutment 518 cooperates with a cylinder 100 ounted in ~; windows 101 also for-ed in the gussets 16, 17 The cylinder 100, which has a tendency to be drawn inside (arrow F2) by a resilient element 81, carrles a cable 102 wound around it and retalned under tension by a second resilient element 81a, thls cable ~`~
~102 belng fixed at its lower end on the seat back armature 12 20~ ~ ~In~the~event of~an impact (Tlg 12),~the res11ient element 81 1s~defor-ed, the abut-ent 518 ~
drives thus the cylinder lO and blocks strongly the ~ ~ ;
cable 102, and this all~the more that the throughgoing tubes~318, 418 are perlpherically serrated so as to provide a~good bold of~the~cable 102 There agaln, the result 18 the sa-e as that previously explalned ;
-` %033~

Finally, in Flg. 13, the lower run 130a of the safety be-lt whlch comes for example from an automatlc winder or is provided with any one of the blockage devices described in the preceding figures, passes along ~ .
a segment in the shape of a shoe 120 artlcùlated at 121 to the armature of the seating portion of the seat.
Ihe front upper portlon:122 of the segment 120 iB serrated in order to cooperate wlth a toothed sector 123 fixed on the axis of articulatlon of each seat back 10 articulation mechanism 12. .--m , There is also provided a resilient element 8lb ::: :
having a tendency to brlng rearwardly the sector 120 in the directlon of arrow F3 (Flg. 13), but which is deformed in the event of an lmpact and, at that moment, ::
the serration 122 extends lnto the teeth of the toothed sector 123 (Fig. 14~, thereby blocklng completely the .
axls of articulation of the aeat back articulation `. -.
mechanism 12, so that the latter do not support any : torque havlng a tendency to deform them. .:
~ ~ In Fig. 15, the toothed~segment 122 ln the~ shape of a:shoe 1s drlven by~a lever ~230 controlled by a~pad ; ;~-: ~ , 231 on the outer surface of whlch wlll extend the run ~: ~ 130a of the safety belt so:that, as explained for the previous ca~es, when there~is an impact, the toothing 122 of the segmeDt 120 w11~1~extend lnside the~toothlng ~
of the toothed sector 123 ~see Flg. 16) 80 as to latch ~ :

~ 14 -" 2033~9 the seat back artlculatlon mechanisms 12 and thereby avoid any destructive torque of the latter. This action `
causes a rubbing effect which lncreases the anchoring of the lower run 130A of the safety belt (Flg. 15).
5 Finally, a lever 230 (Flg. 16) lncreases the force which ~-;
block~ the shoe 120 on the toothed sector 123, the purpose of which on the run 130a of the belt 130 being ~-~ the same as in Fig. 15.
- In all the embodiments of Figs. 8 to 16, the lQ articulation point A of the mechanisms settin8 the lncllination of the seat back in consideratlon occupies the same position as that deflned for Figs. 4 and 5.
Moreover, it is also possible to make safety belts of the parachute type with four embarked points 15 but, in that case, the ventral run is made of two elements which are each connected to the rear lateral , armature of the ~eatlng portion of the seat and the closing lock being ln the middle of the ventral belt ;
this lock can also receive two catches fixed to the~ :
20 lower portion of the shoulder runs, as known. The mounting of each shoulder run is conform to what has been prevlously descrlbed for the rear run 13~0a.
Finally, it should be noticed that these -~
embarked safety belts are provided with the known :, :
~ 25 devlces for ad~ustlng the~length of each run in ~:

2~33~9 , .
consideration so as to set them as a functlon of the corpulence of the passenger.
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Claims

1. A vehicle seat provided with a safety belt with fixation points embarked on the seat armature, wherein one end (130a) of the strap (30) forming the safety belt is rigidly connected to a rear lower portion of the armature (2) of the seating portion of the seat by a blockage mechanism (34, 43, 18, 118, 218, 318, 418), then a shoulder keeper (21) situated frontwardly with respect to the upper portion of the front face of the seat back (4) provides for the sliding and guiding of a run (130b) of the safety belt passing above the passenger shoulder, an other end of the run (130c) of the safety belt being secured to an iron fitting (31) fixed with one of the side flanges of the seating portion armature and forming a second fixation point, then a keeper, cooperating with a lock (39) forming a third lower fixation point of the safety belt, being connected to the side flange opposite the second fixation point on the armature of the seating portion of the seat while the two side flanges receiving the fixed and mobile portions of back seat inclination setting mechanisms with respect to the seating portion of the seat are placed in a position such that a pivoting point (A) of these mechanisms is in a position which is in front of a normal pivoting point (B) of these mechanisms by a certain distance sufficient for substantially cancelling the efforts of the safety belt on these articulation mechanisms.

2. A seat as set forth in to claim 1, wherein the pivoting point (A) of the seat back inclination setting mechanisms with respect to the seating portion is offset by a distance of about 50 mm in front of the normal pivoting point (B).

3. A seat as set forth in claim 1, the blockage mechanism of the strap (30) forming the safety belt placed at the rear of the seat back of said seat comprises a blockable winder (43).

4. A seat as set forth in claim 1, wherein the blockage mechanism of the strap (30) forming the safety belt placed at the rear of the seat back of said seat is made of throughgoing tubes (118, 18, 218) disposed in two parallel vertical planes and in three parallel horizontal planes defining therebetween runs (130c, 130d), whereby the component of the forces of said runs is such that there is created an antagonist force producing a torque which reduces considerably the torque exerted on the seat back articulation mechanisms.

5. A seat as set forth in claim 1, wherein the blockage mechanism of the strap (30) forming the safety belt placed at the rear of the seat back of said seat is made of throughgoing tubes (18, 318, 418) disposed in two parallel planes, the throughgoing tube (18) which is connected to base of the seat back being slidable transversely with respect to the throughgoing tubes (318, 418) in a plane perpendicular to the plane defined by the throughgoing tubes (318, 418) which are rigidly connected to the seating portion of said seat so as to create, when a tension is applied to a rear run (130) of the strap (30), a blockage of said run between the throughgoing tubes (18, 318, 418).

6. A seat as set forth in claim 1, wherein the blockage mechanism of the strap (30) forming the safety belt placed at the rear of the seat back of said seat is made of two throughgoing tubes (318, 418) rigidly connected to the armature of the seating portion of said seat while the tube (518) which is rigidly connected to the armature of the seat back of said seat slidable in openings (180) formed in a base of said seat back armature is subjected to action of the strap which is wound and entrains the cylinder (100) and causes a blockage of the cable (102), the tubes (318, 418) being serrated.

7. A seat as set forth in claim 1, wherein, in addition to a blockage member of the lower end of the run (130a) of the strap (30) forming the safety belt, there is provided on the axis of rotation of the setting mechanisms of the position of the seat back of said seat with respect ot the seating portion of said seat, a toothed sector (123) cooperating with the toothing (122) carried by a shoe-shaped segment (120) articulated on the armature of the seating portion of the seat, the toothings (122, 123) cooperating, when there is an extreme tension of the strap (30), for blocking the articulation mechanisms and for providing a rubbing effect increasing an anchoring of the lower run (130a) of this safety belt.

8. A seat as set forth in claim 7, wherein the shoe (120) is subjected to action of a pad (231) on which passes the run (130a) of the strap (30) forming the safety belt, said pad (231) being connected to the shoe (120) by a lever (230) increasing a force for blocklng said shoe on said toothed sector (123).