now , the present invention will hereinafter be described with reference to the attached drawings . in fig1 reference numeral 1 designates an overall arrangement of a vehicle seat , reference numeral 2 designates a seat cushion and reference numeral 3 designates a seat back . the seat back 3 is separated by three in the up and down or vertical direction , or it is separated into three portions , i . e ., a lower portion 3a corresponding to a lumbar vertebra of a user &# 39 ; s back , an intermediate portion 3b corresponding to an upper half portion of the user &# 39 ; s back and an upper portion 3c prepared as a head restraint . a first angle adjusting mechanism 4 is provided at one side of a coupling portion between the lower portion 3a of the seat back 3 and the seat cushion 2 ; a second angle adjusting mechanism 5 is provided on a coupling portion between the lower portion 3a and the intermediate portion 3b at the same side as the former and a third angle adjusting mechanism 6 is provided on a coupling portion between the intermediate portion 3b and the head restraint 3c at the same side as the former , respectively . the first angle adjusting mechanism , that is , the reclining device 4 is coupled with the second and third angle adjusting mechanisms 5 and 6 through control wires 7 and 8 so that the second and third angle adjusting mechanisms 5 and 6 are respectively operated by the operation of a lever 11 of the reclining device 4 . the reclining device 4 and the second and third angle adjusting mechanisms 5 and 6 are provided with fine adjusting knobs 4a , 5a and 6a , respectively . to the other sides of the lower portion 3a , the intermediate portion 3b and the upper portion 3c , there are respectively provided return springs 4 &# 39 ;, 5 &# 39 ; and 6 &# 39 ; in correspondence with the reclining device 4 and the second and third angle adjusting mechanisms 5 and 6 thereby to always rotatably bias the respective portions 3a , 3b and 3c in the forward direction . the thus constructed seat back 3 can be placed at a first forward - leaning position fl 1 ( reclinable position in the forward direction and hereinafter simply referred to as fl 1 ), a second forward - leaning position fl 2 ( reclinable position in the forward direction and hereinafter simply referred to as fl 2 ), a neutral position n , a comfortable position c and a full reclining position f relative to the seat cushion 2 as shown in fig2 a . the angles of the reclining device 4 and the second and third angle adjusting mechanisms 5 and 6 will be determined as shown in fig2 b and 2c . in this case , the angle of the reclining device 4 can be reclinably moved to the forward - leaning position fl , the neutral position n , the comfortable position c and the full reclining position f in this order as shown in fig2 b , while the angles of the second and third angle adjusting mechanisms 5 and 6 can be reclinably moved to the forward - leaning position fl , the comfortable position c , the neutral position n and the full reclining position f in this sequential order as shown in fig2 c . to this end , the movable or lift - up of the lever 11 of the reclining device 4 is made as two stages from the locking position ( the neutral position n ) through a middle stage ( the comfortable position c ) to the upper stage ( the full reclining position f ) as shown in fig3 by which the posture of the seat back 3 can be set by the lift - up of the lever 11 . in other words , when the lever 11 of the reclining device 4 is lifted up from the locking position to the middle stage , the posture of the seat back 3 can be varied from the neutral position n to the comfortable position c or the first forward - leaning position fl 1 , while when the lever 11 is further lifted up to the upper stage , the posture of the seat back 3 can be varied to the full reclining position f or the second forward - leaning position fl 2 . the constructions of the respective mechanisms operable as described above will be described in detail with reference to fig3 to 9 . in the first place , the first angle adjusting mechanism 4 will be described with reference to fig4 to 6 . the first angle adjusting mechanism , that is , the reclining device 4 comprises a base bracket 12 to be fixed to the cushion frame ( not shown ) of the seat cushion 2 , a movable arm 13 to be fixed to the frame ( not shown ) of the lower portion 3a of the seat back 3 , an intermediate gear 14 , an idler 15 and the above mentioned lever 11 , each being coaxially and movably assembled by a hinge pin 16 . the fine adjusting knob 4a is attached to the tip end of the hinge pin 16 . the movable arm 13 has an externally toothed gear annulus 13a ( which is projected to the side of the gear 14 ) and the intermediate gear 14 has an internally toothed gear annulus 14a the number of the teeth of which are more than that of the gear annulus 13a . thus , the movable arm 13 is of a reclining system of a so - called taumel type in which the arm 13 is turnable relative to the intermediate gear 14 under the state that the externally toothed gear annulus 13a is meshed with the internally toothed gear annulus 14a in a certain range . when the hinge pin 16 is rotated by the fine adjusting knob 4a , the mutual rotational angle of the arm 13 and the intermediate gear 14 can be varied in a stepless fashion . the intermediate gear 14 forms an externally toothed annulus 14b around its external periphery and the externally toothed annulus 14b is meshed with a tooth portion 18a of a lock gear member 18 which is pivoted to the base bracket 12 by a pin 17 planted thereon . through the idler 15 , there is bored an arc - shaped long slit or opening 15a with the shaft opening of the idler 15 as the center and into which a protrusion 19 projected from the arm 13 is inserted . although the arm 13 and the idler 15 are mutually rotatable within the range of this long opening 15a , the arm 13 and the idler 15 are normally engaged with each other under the state that they are always biased to one side by a spring 20 extended or stretched between the protrusion 19 and a small cut - up portion 15b formed at the peripheral edge of the idler 15 . the lever 11 is formed integrally with a lock plate 21 and this lock plate 21 forms therethrough a step - shape long slit or opening 21a which is engaged with a lock pin 22 protruded from the free end of the lock gear member 18 . to the shaft pin 17 of the base bracket 12 , there is pivoted a selector member 23 coaxial with the lock gear member 18 . on the free end portion of the selector member 23 , there are planted a first pin 24 and a second pin 25 with a predetermined spacing kept therebetween . since the selector member 23 is biased upward by a spring 26 , the first pin 24 always slidably contacts with the front side , a lower edge convex portion 21b , an intermediate lower edge concave portion 21c and a rear side lower edge convex portion 21d of the lock plate 21 , while the second pin 25 is in slidable contact with a front convex portion 15c and an intermediate concave portion 15d of the peripheral edge of the idler 15 at its lower edge in accordance with the lifted - up amount of the lever 11 . to the arm 13 , there is pivotably attached a knock member 27 so as to become turnable . from the top of the knock member 27 , there is projected a knock pin 28 which is biased by a spring 29 to come in slidable contact with an engaging portion 30 formed on the upper peripheral edge of the base bracket 12 . on the engaging portion 30 of this base bracket 12 , there are formed engaging concave portions 30a and 30b with a predetermined spacing kept therebetween . the lever 11 is always biased downward by a lock spring 31 . the operation of the first angle adjusting mechanism , i . e ., the reclining device 4 constructed as described above will be described . first of all , the operation to move the reclining device 4 from the neutral position n ( fig5 ) to the forward - leaning position fl ( fig6 ) and again from the forward - leaning position fl to the neutral position n will be explained . when the lever 11 is lifted up from the neutral position n to the middle stage or comfortable position c ( refer to fig3 ), as shown in fig6 the long opening 21a of the lock plate 21 pushes down the lock pin 22 planted on the lock gear member 18 to an inclined portion between an upper stepped portion 21a &# 39 ; and a lower stepped portion 21a &# 34 ; of the opening 21a with the result that the lock gear member 18 is rotated to thereby disengage the top tooth portion 18a thereof from the intermediate gear 14 , thus releasing the locked state of the arm 13 and so on . under this state , the arm 13 , the idler 15 and the intermediate gear 14 are rotatably leaned together in the forward direction . under this forward - leaning state , since the front convex portion 15c of the idler 15 pushes down the lock pin 22 engaged with the opening 21a of the lock plate 21 , the lever 11 can be prevented from being returned to the original condition , maintaining the lock - released state . under this state , however , if the arm 13 is rotated in its erecting direction , that is , in the clockwise direction , the front convex portion 15c of the idler 15 is disengaged from the lock pin 22 so that the lever 11 is returned to the original position , thus the lever 11 being locked again at the neutral position n . next , the operation to move the seat back 3 from the neutral position n to the comfortable position c will be described . when the lever 11 is lifted up to the middle stage position , the engagement between the externally toothed annulus 14b of the intermediate gear 14 and the tooth portion 18a of the lock gear member 18 is released as described above , while under this state , the first pin 24 on the selector member 23 is made corresponding to the center of the intermediate concave portion 21c of the lock plate 21 , so that the selector member 23 is rotated upward by the spring force of the spring 26 to thereby make the second pin 25 formed at the tip end of the selector member 23 contact with the intermediate convex portion 15d of the idler plate 15 ( fig6 ). then , when the arm 13 is leaned backward , the second pin 25 of the selector member 23 is abutted with the end portion of the intermediate convex portion 15d of the idler 15 , that is , a stepped portion 15e &# 39 ; formed between the intermediate concave portion 15d and the rear convex portion 15e , thus the arm 13 being restrained from leaning backward more than ever . if under this state the lever 11 is released , the lever 11 is returned to the original position by the spring force of the lock spring 31 so that the upper stepped portion 21a &# 39 ; of the long opening 21a bored through the lock plate 21 is engaged with the lock pin 22 of the lock gear member 18 , rotating the lock gear member 18 upwards to thereby engage the tooth portion 18a formed at the tip end thereof with the externally toothed annulus 14b of the intermediate gear 14 . therefore , the arm 13 is locked at the comfortable position c . thirdly , the operation to move the seat back 3 from the neutral position n to the full reclining position f or from the comfortable position c to the full reclining position f will be described . when the lever 11 is lifted up to the upper stage , the first pin 24 formed on the selector member 23 pushes down the rear convex portion 21d of the lock plate 21 and the selector member 23 is rotated downward against the biasing force of the spring 26 , thus the second pin 25 formed on the tip end of the selector member 23 being prevented from contacting with the peripheral edge of the idler 15 . on the other hand , since the lock pin 22 is lowered by the lower stepped portion 21a &# 34 ; of the long opening 21a of the lock plate 21 , the lock gear member 18 is rotated downward to thereby disengage the toothed portion 18a formed at the top of the lock gear member 18 from the externally toothed annulus 14b of the intermediate gear 14 so that the arm 13 becomes able to rotate . therefore , the arm 13 or seat back 3 can be rotated up to the full reclining position f . thus , if the lever 11 is released , the arm 13 is locked at the full reclining position f similarly as described above . further , when the arm 13 or seat back 3 is returned from this full reclining position f to the original neutral position n , the lever 11 is lifted up to thereby rotate the lock gear member 18 through the lock pin 22 so that the toothed portion 18a at the tip end of the lock gear member 18 is disengaged from the externally toothed annulus 14b of the intermediate gear 14 . then , under the state that the arm 13 is released from the locked state , the arm 13 is rotated in the erecting direction . in this case , the arm 13 can automatically be rotated in the erecting direction by the biasing force of the return spring 4 &# 39 ; which is mounted on the other side of the pivot portion of the lower portion 3a at the seat back 3 in opposing relation to the reclining device 4 . further , when the arm 13 is erected from the backward , the comfortable position c and the neutral position n can be sensed by the resistive force generated by the engagement between the knock pin 28 of the knock member 27 and the engaging concave portions 30a and 30b of the engaging portion 30 of the base plate 12 . subsequently , the constructions of the second and third angle adjusting mechanisms 5 and 6 will be described . in this case , since both of them are constructed in the same way , only the second angle adjusting mechanism 5 will be explained for simplicity with reference to fig7 to 9 . while the second angle adjusting mechanism 5 is fundamentally constructed in the same way as the first angle adjusting mechanism , that is , the reclining device 4 , the angle of the arm 13 in the reclining device 4 is determined unlike the sequential order of the forward - leaning position fl , the neutral position n , the comfortable position c and the full reclining position f ( fig2 b ) but the angle of the corresponding arm is determined in the sequential order of the forward - leaning position fl , the comfortable position c , the neutral position n and the full reclining position f ( fig2 c ). accordingly , the second angle adjusting mechanism 5 is additionally provided with members , such as a neutral plate member 35 , a pull spring 36 and a hook 37 for the purpose of locking the corresponding arm at the neutral position n from the forward - leaning position fl skipping over the comfortable position c . although this neutral plate member 35 is rotated around a hinge pin 46 by the rotational amount corresponding to the dimensional difference between a long slit or opening 35a bored through the neutral plate member 35 and a patch 49 of an arm 43 which is attached to the frame ( not shown ) of the intermediate poriton 3b of the seat back 3 , the neutral plate member 35 is normally biased in the backward direction by the pull spring 36 . a lock plate 51 is coupled to the lever 11 of the first angle adjusting mechanism , namely , the reclining device 4 through the control wire 7 , one end of which is pivoted to the lever 11 and the other end of which is pivoted to a pin 51a planted on the lock plate 51 , and thereby operated by the operation of the lever 11 . the operation of the second angle adjusting mechanism 5 thus constructed will be described . in the first place , an explanation will be given on a case in which the arm 43 or intermediate portion 3b of the seat back 3 is moved from the neutral position n ( fig9 ) to the comfortable position c and is then returned to the neutral position n again and a case in which the arm 43 is moved from the neutral position n to the forward - leaning position fl ( fig9 ) and is then returned to the neutral position n once again . when the lever 11 of the first angle adjusting mechanism , i . e ., the reclining device 4 is lifted up to the intermediate stage c ( fig3 ), by the control wire 7 , the lock plate 51 of the second angle adjusting mechanism 5 under the state shown in fig8 is rotated to the intermediate position and its long slit or opening 51a urges a lock pin 52 planted on a lock gear member 48 to the inclined portion between an upper stepped portion 51a &# 39 ; and a lower stepped portion 51a &# 34 ; of the opening 51a so that the lock gear member 48 is lowered . therefore , a toothed portion 48a formed at the tip end of the lock gear member 48 is disengaged from an externally toothed annulus 44b of an intermediate gear 44 , thus releasing the arm 43 and so on from the locked state . then , the arm 43 , the intermediate gear 44 , an idler 45 and the neutral plate member 35 are integrally leaned in the forward direction . this leaning in the forward direciton can be automatically carried out as the intermediate portion 3b of the seat back 3 is inclined by the biasing force of the return spring 5 &# 39 ; mounted on the other end portion of the pivot portion of the intermediate portion 3b on the seat back 3 in accordance with the second angle adjusting mechanism 5 . at that time , a first pin 54 planted on the selector member 53 slidably contacts with a lower edge concave portion 51c of the lock plate 51 , while a second pin 55 plated on the selector member 53 at its tip end slidably contacts with an outer peripheral concave portion 45d of the idler 45 . under this state , when the arm 43 is rotated forward and the pin 55 at the tip end of the selector member 53 is engaged with the rear end portion of the outer peripheral concave portion 45d of the idler 45 so that the rotation of the arm 43 is restricted . when the lever 11 of the reclining device 4 is lifted up to the upper stage , the lock plate 51 is rotated to the final position to allow the intermediate pin 54 of the selector member 53 to be slidably pushed by the rear convex edge portion 51d of the lock plate 51 so that the selector member 53 is rotated and the pin 55 formd at the top thereof slidably contacts with an outer peripheral front side portion 45c of the idler 45 over its outer peripheral concave portion 45d , thus the arm 43 being rotated to the forward - leaning position fl . at that time , the neutral plate member 35 is pulled by the pull spring 36 through the hook 37 and thereby rotated in the forward direction . under this forward - leaning state , a front convex edge portion 45c of the idler 45 pushes down the lock pin 52 of the lock gear member 48 so as to sandwich the same between the portion 45c and the long opening 51a of the lock plate 51 , so that the lock plate 51 is not returned to the original position but keeps the lock releasing state ( see fig9 ). if under this forward - leaning state the arm 43 is lifted upward gradually , the lower edge concave portion 45d of the idler 45 is made corresponding to the pin 55 formed on the top of the selector member 53 ( the neutral position n of the second angle adjusting mechanism 5 ). if the arm 43 is further leaned backward , the rear end of the lower edge concave portion 45d of the idler 45 is engaged with the pin 55 projected at the tip end of the selector member 53 to thereby push the lower portion 3a of the seat back 3 in the backward direction . therefore , the arm 13 of the reclining device 4 is erected from the forward - leaning state to the neutral position n and can be locked as described above . since this reclining device 4 is locked , the control wire 7 is returned to the original condition and the second angle adjusting mechanism 5 is locked . in other words , the second angle adjusting mechanism 5 is again locked at the neutral position n . next , an explanation will be given on the operation of the second angle adjusting mechanism 5 in which the seat back 3 is moved from the neutral position n to the full reclining position f or from the comfortable position c to the full reclinging position f . when the lever 11 of the reclining device 4 is lifted up to the upper stage , the lock plate 51 of the second angle adjusting mechanism 5 is rotated to the final position so that as described above , the long opening 51a of the lock plate 51 pushes down the lock pin 52 of the lock gear member 48 to thereby disengage the toothed portion 48a formed on the tip end of the lock gear member 48 from the externally toothed annulus 44b of the intermediate gear 44 . thus , the locked state is released so that the arm 43 can be leaned to the full reclining position f . in this case , the lock plate 51 must be rotated to the final position otherwise the tip end pin 55 of the selector member 53 is engaged with the rear end of the lower edge concave portion 45d of the idler 45 so that the arm 43 can not be leaned to the full reclining position f . in other words , if the lock plate 51 is rotated to the final position , the rear convex edge portion 51d of the lock plate 51 pushes down the intermediate pin 54 of the selector member 53 to thereby rotate the selector member 53 downward so that its tip end pin 55 is disengaged from the lower edge concave portion 45d of the idler 45 , thus the arm 43 can be leaned freely . under the state that the arm 43 is leaned down to the full reclining position f , if the lever 11 of the reclining device 4 is released , the reclining device 4 is locked and also the control wire 7 is returned to the original position , whereby the lock plate 51 is rotated to the original position to thereby place the second angle adjusting mechanism 5 in the locked state . by rotating the fine adjusting knob 5a , the arm 43 is rotated under the state that the engagement range of the internally toothed gear annulus 43a of the intermediate gear 44 relative to its externally toothed gear annulus 44a is being changed , thus to vary the inclined angle of the arm 43 . in other words , it is possible to finely adjust the inclined posture of the intermediate portion 3b of the seat back 3 by rotating the fine adjusting knob 5a . in this case , the inclinable and turnable range of the arm 43 is restricted by the engagement between a pin 58 projected on the arm 43 and an engaging concave portion 60 formed on the upper edge of the base plate 42 . another embodiment of the second and third angle adjusting mechanism 5 and 6 according to the present invention will hereinafer be described with reference to fig1 and 11 . also in this embodiment , the second and third angle adjusting mechanisms 5 and 6 are constructed in exactly the same way so that an explanation will be given only on the second angle adjusting mechanism 5 for simplicity . in this embodiment , the aforesaid second angle adjusting mechanism 5 is simplified in mechanism by omitting the idler 45 and the neutral plate member 35 used in the above embodiment . in this embodiment , as shown in fig1 and 11 , the second angle adjusting mechanism 5 mainly comprises a base bracket 72 , an arm 73 , an intermediate gear 74 and a lock plate 75 , each of these main members being assembled by a hinge pin 76 coaxially . the arm 73 is formed thereon an internally toothed gear annulus 73a with the bore for the pin 76 as the center , while the intermediate gear 74 is formed with an externally toothed gear annulus 74a which is less in the number of the teeth than the internally toothed gear annulus 73a of the arm 73 . the internally toothed gear annulus 73a and the externally toothed gear annulus 74a are engaged with each other in a part of a range under being eccentric state and due to the difference in the number of teeth therebetween and are adaped to carry out the mutual rotational movement , wherein the angles of the arm 73 and the intermediate gear 74 can be varied from each other by the rotation of the hinge pin 76 in a stepless fashion . with the externally toothed annulus 74b formed around the outer periphery of the intermediate gear 74 , there is engaged a tip end toothed portion 78a of a lock gear member 78 which is pivoted on a shaft pin 77 implanted on the base bracket or base plate 72 . a lock pin 79 is planted on the lock gear member 78 and a selector member 80 is pivotably supported on the shaft pin 77 on which the lock gear member 78 is pivotably supported . a pin 81 is planted on the intermediate portion of this selector member 80 , and a tip end portion 80a of the selector member 80 is made corresponding to convex edge portions 73b and 73c which are separately formed on the front and rear of the lower side peripheral edge of the arm 73 . through the lower portion of the lock plate 75 , there is formed a stepped elongated slit or opening 75a with which the lock pin 79 implanted on the lock gear member 78 is engaged . on the upper portion of the lock plate 75 , there is implanted a pin 82 to which is pivotably coupled the tip end of the control wire 7 connected to the lever 11 of the reclining device 4 . the pin 81 of the selector member 80 slidably contacts with the lower edge portion of the lock plate 75 in which a convex edge portion 75b is formed on the rear portion thereof . an outer surface plate 83 is located at the outer side surface of this lock plate 75 and this outer surface plate 83 is fixed to the base plate 72 . through this outer surface plate 83 , there is formed a long slit or opening 83a which is to be engaged with the tip end portion of the pin 81 of the selector member 80 . between the tip end portion of the pin 81 projected from this long opening 83a and a projection 83b projected from the upper portion of the outer surface plate 83 , there is tensioned a spring 84 by which the pin 81 is always made in slidable contact with the lower edge portion of the lock plate 75 . a lock spring 85 is tensioned between an arm piece member 75c of the lock plate 75 and a projection piece member 83c projected from the lower edge portion of the outer surface plate 83 to thereby always rotate the lock plate 75 in the locking direction , that is , the direction opposite to the direction in which it is pulled to rotate by the control wire 7 . a pin 86 is protrusively attached to the arm 73 . this pin 86 slidably contacts with a concave portion 87 which is formed on the upper edge portion of the base plate 72 , restricting the rotational range of the arm 73 . the tip end portion of the hinge pin 76 is projected to the outside through the shaft opening of the outer surface plate 83 and to which the fine adjusting knob 5a ( not shown ) is fixed . the operation of this embodiment of the second angle adjusting mechanism 5 according to the present invention constructed as mentioned above will be described . a first explanation will be given on the recovering operation in which the seat back is moved from the neutral position n to the comfortable position c or to the forward - leaning position fl and is returned to the neutral position n . when the lever 11 of the reclining device 4 is lifted up to the intermediate stage c ( refer to fig3 ), the lock plate 75 is rotated to its intermediate position by the control wire 7 so that its elongated opening 75a pushes down the lock pin 79 of the lock gear member 78 to rotate the lock gear member 78 downward , disengaging the tip end toothed portion 78a thereof from the externally toothed annulus 74b of the intermediate gear 74 , thus to release the locked state . under this state , the arm 73 is rotatably leaned in the forward direction by the engagement between the internally toothed gear annulus 73a of the arm 73 and the externally toothed gear annulus 74a of the intermediate gear 74 . this leaning in the forward direction is automatically carried out by the biasing force of the return spring 5 &# 39 ; provided in correspondence with the second angle adjusting mechanism 5 through the intermediate portion 3b of the seat back 3 . at that time , since the pin 81 of the selector member 80 slidably contacts with the lock plate 75 in a range from its lower edge convex portion 75b to its peripheral edge , the selector member 80 is rotated upward by the biasing force of the spring 84 to make the top portion 80a thereof contact with the lower side peripheral edge portion of the arm 73 between the convex portions 73b and 73c thereof . when the arm 73 is rotated forward , the front convex portion 73b of the arm 73 is engaged with the top end portion 80a of the selector member 80 , restricting the rotation of the arm 73 . further , when the lever 11 of the reclining device 4 is lifted to the upper stage f ( refer to fig3 ), the lock plate 75 is rotated to the final position . also in this state , the lock pin 79 of the lock gear member 78 is pushed down by the elongated opening 75a and the pin 81 of the selector member 80 is in slidable contact with the peripheral edge of the lock plate 75 so that the top end portion 80a of the selector member 80 slidably contacts with the lower edge portion of the arm 73 between its convex portions 73b and 73c . thus , the arm 73 is released from being locked and is made turnable within a range between the convex portions 73b and 73c . if under this state the arm 73 is lifted up , the rear convex portion 73c of the arm 73 contacts with the tip end portion 80a of the selector member 80 to thereby restrict the rotation of the arm 73 . if the arm 73 is furthre leaned backward , this raises the arm 13 of the reclining device 4 from the forward - leaning state to the neutral position n through the lower portion 3a of the seat back 3 so that the arm 13 can be locked to this neutral position n . if the arm 13 of this reclining device 4 is locked , its lever 11 is rotated downward by the spring or biasing force of the lock spring 31 so that the control wire 7 is returned . hence , the lock plate 75 of the second angle adjusting mechanism 5 is rotated to return to the original position by the biasing force of the lock spring 84 so that the arm 73 is locked at the neutral position n . a next explanation will be given on the operation in which the seat back 3 is moved from the neutral position n to the full reclining position f or from the comfortable position c to the full reclining position f . when the lever 11 of the reclining device 4 is lifted to the upper stage , the lock plate 75 of the second angle adjusting mechanism 5 is turned to the final position to thereby release the arm 73 from being locked as mentioned above so that the arm 73 can be pulled down to the full reclining position f . even when the lock plate 75 is not rotated to the its final position , in other words , even when it is rotated to its intermediate stage , the locking state of the arm 73 for the intermediate gear 74 is released . if the lever 11 of the reclining device 4 is rotated to the intermediate stage , only with respect to the second angle adjusting mechanism 5 , the arm 73 can be leaned to the full reclining position f . in this case , however , the seat back 3 is not placed at the comfortable position c on the whole but merely inclined between the neutral position n and the full reclining position f , thus making the final posture of the user unstable . further , also in this embodiment , if the hinge pin 76 is rotated by the fine adjusting knob 5a , while the range in which the internally toothed annulus 73a of the arm 73 is engaged with the externally toothed annulus 74a of the intermediate gear 74 is moved , the arm 73 is rotated and hence its inclined angle can be varied . in this case , the turnable inclined range of the arm 73 is restricted by the engagement between the pin 86 projected on the arm 73 and the concave portion 87 formed on the upper edge of the base plate 72 . according to the present invention as described above , in the so - called multi - joint type vehicle seat in which the seat back is divided into the plurality of portions in the vertical direction , the angle adjusting mechanisms provided at the respective coupling portions can be operated by operating the single lever so that the seat back can be set to some final postures positively and varied with ease . also , by finely adjusting each angle adjusting mechanism , the respective portions of the seat back can be changed to the state from the respective postures thus set in accordance with the taste of the user , and so it is possible to suppress the fatigue of the user as small as possible . in addition , since each angle adjusting mechanism is formed of the stepless - locking means to be operable by the rotation of the lock plate and the fine adjusting means realized by the engagement between the internally toothed gear annulus and a part of the externally toothed gear annulus , the construction thereof is simplified . further , since the respective angle adjusting mechanisms are merely connected by the control wire , the assembling thereof is simple and the manufacturing cost thereof can be reduced . hence , particularly when the present invention is applied to the vehicle seat , there can be achieved a great effect . the above description is given on the preferred embodiments of the invention but it will be apparent that many modifications and variations could be effected by one skilled in the art without departing from the spirits or scope of the novel concepts of the invention so that the scope of the invention should be determined by the appended claim only .