CA1154663A

CA1154663A - Vehicle seats

Info

Publication number: CA1154663A
Application number: CA000327616A
Authority: CA
Inventors: Geoffrey W. Barley
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 1978-05-20
Filing date: 1979-05-15
Publication date: 1983-10-04
Also published as: ES252860Y; IT7909424A0; FR2425958A1; IT1120847B; JPS5935231U; SE7904221L; IN151932B; BR7903047A; DE2920239A1; NL7903958A; ES252860U; NZ190506A; AR223677A1; CH637334A5; SE440058B; FR2425958B1

Abstract

ABSTRACT OF THE DISCLOSURE

This invention relates to a vehicle seat of the type in which a seat part is supported and guided for upward and downward movement relative to a base part by a spring suspension.
In order to avoid loss of contact between the feet of the seat occupant and control pedals of the vehicle, the suspension includes linkages connecting the seat part to the base part for relative movement such that the seat occupant's ankles remain stationary whereas his knees swing about an axis through his ankles.

Description

l663 BACKGROUND OF THE INVE~TION
.. . .. __ This invention relates to vehicle seats of the type in which a seat part (normally comprising a seat rest and a back rest) is supported and guided for upward and downward movement relative to a base part by means of a spring suspension. The suspension includes spxing means capable of counterbalancing the load of the seat part and its occupant so that the seat part, under static conditions, is located at a mid-ride position substantially midway between UP-stop and DOWN-stop positions.
Said spring means can comprise any means of taking up, storing and giving out energy so that the seat and its occupant can oscillate between the UP-stop and DOWN-stop positions when subjected to external forces.
Such a vehicle seat assists in i.solating the occupant from vibrations transmitted from the vehicle wheels, particu-larly as the vehicle passes over rough terrain. However, the necessary freedom of the seat part to move up and down carries with it the danger, in the case of a driver's seat, of the driver's feet losing correct contact with the control pedals.
Previous attempts to overcome this difficulty have largely been based on the concept that the seat part of a suspension seat should move pivotally about a horizontal axis through the knee-hinges of the driver, since if such a knee-hinge axis (sometimes referred to herein as the K axis) is fixed relative to the base part of the seat, the lower leg, and hence the ankles, '~

L6~3 of the driver can remain stationary irrespective of the movemen~s of the seat. However, if the seat rest and back rest of a seat part move in this way, the driver's back inclination will vary with rise and fall of the seat. This difficulty can be overcome by incorporating a linkage to change the inclination of the back rest with changes in the inclination of the seat rest. ~n example of a suspension seat designed in th.is way is found in British Patent Specification 1,156,942.
Such suspension seats have the disadvantage of a rela-tively large fore and aft movement of the entire part of the driver's body above his hip (H axis) since the knee hinge axis is the axis about which the seat rest and the hip region of his body must swing.
The present invention is based on the realisation that if a suspension seat can be designed to move in such a way that the seat occupant's lower leg will move about a horizontal transverse axis through the occupantls ankle hinges (A axis), the knee hinge axis accordingly being free to swing about the ankle hinge axis, such a seat will a~ford the driver a high degree of control over the vehicle over a wide range of seat movemen~. Moreover, it is found that a seat movable in this way affords a high degree of comfort to the driver.
Accordingly an object of the invention is to provide a uspension seat capable of moving the seat occupant's lower leg about a ~59~6~i3 horizontal transverse axis through his ankle hinges, at the same time causing the seat occupantls back to move up and down with the back res-t ol the seat at a substantially constant inclination to the vertical. References herein to 'the ver-tical' assume the vehicle to be on horizontal ground.
In the present invention a suspended vehicle seat provides isolation from vertical vibrations to an occupant thereof and includes a seat part, which includes a seat rest which is mounted for tilting movement and a back rest, a base part, and means connecting the seat part to the base part.
The means connecting the spring part to the base part includes a spring suspension by which the back rest is supported on the base part and which is effective to restrict movement of the back rest to a substantially vertical direction. The suspension includes a spring,and a plurality of relatively movable structural elements, certain of the elements connecting to the seat rest and to the back rest for providing pivotal movement of the seat rest about at least two spaced apart horizontal transverse axes through instantaneous centers of rotation. The centers are the instan,taneous centers of rotation of the thigh of a seat occupant for whom the seat is designed which is positioned on the seat rest relative to any two of the structural elements of the seat which move relative to each other during upward and downward movement of the seat part relative to the base part. The pivotal movement of the seat rest causes the thigh of a seat occupant to remain in contact with the seat rest and to be movable longitudinally and pivotally in such a way that the ankle - 3~

66~
hinge axis of the seat occupant will remain stationary relative to the base part as the seat moves above and below its mid ride position in response to vertical vibrations.
A specific embodiment of the present invention also provides a vehicle seat comprising a seat part having a seat frame mounted for upward and downward movement relative to a base part by means of a spring-biased scissor-action suspension (as - 3a -~S~L663 defined) the linkage arms of the suspension being arranged to effect upward and downward movement of the seat frame substantially without tilting movement, the seat part further having a seat pan for supporting a seat cushion, the seat pan having pivot connections to the seat suspension such that during upward and downward movement of the seat, movement of the rearward part of the seat pan takes place in an upward and downward direction such that the movement of the H axis is vertical, and the seat pan tilts to cause the K axis to move along an arc permitting the A axis to remain stationary, the H, K and A axes being as herein defined.
By the expression 'scissor-action suspension' is meant a suspension which comprises a pair of rigid links having a common pivot connection in the manner of a pair of scissors,or a plurality of pairs of such links having a common pivot axis, one end of each link of the or each pair having a pivot connection to a seat part of the seat and the opposite end of each link of the pair having a pivot connec-tion to the base part of the seat, the axes of the pivot connections all being parallel to one another, some of the pivot connections being fixed pivot connections but the others being sliding or rolling connections sufficient to give freedom of movement to the suspension in a substantially vertical direction only, an example being described in British .. ~
Patent No. 957,332.

~L154~;;63 B~IEF SUMMARY ~F THE DRAWINGS

Figure 1 is a diagrammatic representation oE a vehicle seat suspension of the scissor-action linkage type formed by two transversely spaced pairs of crossed arm linkages having cornmon pivotal axes to the base part, to the seat part and to each other, and showing the instantaneous centres of rotation of the moving parts of the suspension and of links representing the upper and lower leg portions of a seat occu-pant;
Figure 2 is a diagrammatic side elevation, part sectional, of a vehicle seat constructed in accordance with the invention;
Figure 2A shows a modification of the vehicle seat of Figure 2 which involves a different instantaneou~s centre of rotation;
Figure 3 is a diagrammatic representation of the movement o-E the vehicle seat of Figure 2;
Figures 4 and 5 are diagrammatic illustrations of the combination respectively of the seat rest mounting of Fig.
2A with other types of suspension;
Figures 6 to 11, are diagramrnatic illustrations of suspensions in which the seat rest is pivoted about a pair of instantaneous centres of rotation different from that of Figure , .

' ' .

~5g~6~3~

2; Figure 8 and Figure 2~ utilising the same instantaneous centres of rotation;
Figure 12 is a diagrammatic representation, corres-poncling to that of Figure 1, of the instantaneous centres of rotation of the parts of another type of suspension, and Figure 13 is a diagrammatic representation of a seat suspension in which the seat rest is pivoted at instan-taneous centres of rotation shown in Figure 12.

DESCRIPTION OF PREFERRED EMBODIMENTS

In each of the drawings, the seat part is shown to be supported by links lying in the plane of the drawing, and normally a second set of links or more than two sets of links of the same construction will be located in parallel relation-ship to the first set of links in order to provide stable support for the seat part. ~lowever it will be appreciated that if the single set of linlcs appearing in the plane of the drawing can be provided with adequa~e depth in a direction perp~ndicular to the plane of the drawing, only one such set of links may be needed to provide adequate support.
Before describing the invention in detail, it is necessary to consider the basic design concepts of a seat for achieving the object of the invention. In order to achieve rise and fall of the driver's back without variation of its inclination, it will normally be necessary to adopt one of a663 three well-k~own basic seat suspension designs For con-venience these will be referred to as types A, B and C in which:-Type A provides a back rest mounted on a seat frame,the seat frame being guided for vertical movement by a system of scissor-action linkages, such as are described in detail in British Patent Specification No. 957,332 and shown in Figure 1 of the drawings accompanying the present Specification.
Type B provides a back rest which is mounted for upward and downward sliding movement on one or more supports extending upwardly from the base part substantially vertically and located behind the back rest.
Type C provides a back rest ~ ich is connected by a parallelogram linkage system to a ~jupport upstanding from the base part, the links of the system being horizontal or at an angle ~o the horizontal sufficiently small ~o minimise ~ore and aft movement of the back rest with rise and fall of the seat. An example of such a suspension can be seen in United States Patent Specification 3,788,697.
Since, in accordance with the invention, the seat rest must rise and fall as the back rest rises and falls, but with a desired relative movement between the seat rest ~L5~6~i~

and back rest to maintain the A axis stationary, the means for achieving this movement of the seat rest will utilise as much as possible of the Type A, B or C suspension means on which the back rest is supported, but with additional supporting means to effect said desired relative movement.
If however a Type B suspension is employed to support the back rest, the means for supporting the seat rest can con-veniently include a Type A or Type C suspension or parts thereof It is now necessary to consider the way in which a driver's body will move in relation to the parts of such suspension in order to achieve the objective o~ the inven-tion. Use will be made in this connection of the Method of Instantaneous Centres o~ Rotation in considering the move-ment of the upper leg or thigh of the seat occupant relative to the parts of the suspension It is considered, in this connection, that the thigh of the seat occupant extends between point K, which is the knee hinge, and point H which is either the hip joint or preferably a point (sometimes referred to as PPP meaning "pre~erred pivot point") which is somewhat behind the true hip joint.
This is the point about which the thigh effectively rotates 6~i3 g as it rocks with the seat rest It is assumed that point H
is relatively stationary with respect to the seat frame.
It should be borne in mind 1) that the Method of Instantaneous Centres of Rotation is based on the concept that any displacement of a body, movable in a plane, between two positions may be considered as a purely rotational movement about some centre;
2) that the centre of rotation of a first link of a mechanism relative to a second link of the mechanism to which it is pivoted lies at the pivot;

3) that the centre of rotation of a body having linear movement lies at infinity on a line perpendicular to the direction of movement and

4) that if the instantaneous centre of rotation of any part x re-lative to any part ~ is defined as the point Ix then if the mechanism has relatively moving parts a, b, c and d, the lnstantaneous centre I is at the intersection a.d.
of the line connecting Ia b and Ib d with the line connecting la.c. c.d. -Considering first the A type suspension1 shown in Flg. 1, this will be seen to comprise a base part 1, and two pairs of . ~

scissor links spaced transversely of the seat, only one being visibleg this pair consisting of first and second links 2, 3.
Link 3 is connected at its forward end by a roller or slider 4 to the base part 1 and by a fixed pivot ~ at its rearward end to a seat frame 6. Link 2 is connected at its forward end by a roller or slider 5 to the seat frame 6 and by a fixed pivot P2 at its rearward end to the base part 1. Links 2 and 3 have a pivotal interconnection P3 at their intersection. The upper leg or thigh of the seat occupant will be looked upon as a link 7,and the lower leg as a linlc 8 pivoted at the ankle hinge point A to the floor, and thu~ to the base part 1. Point ~l is regarded as Eixed relative to Erame 6 It will readily be seen from concept (2) above that the instantaneous centres I2 1~ I4 3~ I~.3~ I5.2 and I3.2 are established at the pivot points of the respective parts of the suspension. Similarly from concept (3) above, it will be seen that instantaneous centres I6 5 and I4 1 will be at infinity on lines perpendicular to the respective guide tracks of sliders

5 or 4, or at the point of contact of guide track and rollers 5 or 4, and I6 1 will be at infinity on lines normal to the direction of travel of seat frame 6.
By use of concept (4) above, the other instantaneous centres can be established, the most important ones being 7.1' I7.2, I7.3~ I7 4, I7 5 and I7 6.
It will be appreciated from this that if the thigh ., - .:

~5g~63 represented by link 7 can be supported on at least two parts of ~he suspension (including the base part) at the respective instantaneous centres of rotation of the link 7 relative to such parts, the thigh or link 7 will move as a link of the suspension mechanism in such a way that no displacement of the ankle point A will occur, since point A is a fixed point by.definition in establishing the instantaneous centres.
Since the thigh 7 can only be supported relative to the parts of the suspension by supporting it on a seat rest, reference will now be made to Figures2 and 3 which illustrate a practical form of seat constructed in accordance with the teaching of the present i.nvention, Reference has already been made to the base part 1, links 2, 3, roller or slider members 4, 5, and seat frame 6, The seat part is seen to consist o the seat frame 6 together with the seat rest 10 and back rest 11, back rest 11 being supported on frame 6. The seat rest 10 consists of a pan or frame 12 covered by a seat cushion 13, and back rest 11 con-sists of a back pan 14 and back cushion 15.
The spring means for supporting the seat part 6, 10, 11 on the base part 1 is a torsion bar 17 extending within a tube 18 to which the upper rearward end of each link 3 is secured, The tube 18 is journalled at its ends in the seat frame 6. One end of bar 17 is secured to one end of tube ~ 5~663 18 and the opposite end of bar 17 is connected to the frame

6 via a preload adjustment mechanism (not shown~, Manual Operation of this mechanism by the seat occupant enables the preload in the torsion bar 17 to be varied.
Since the scissor action links 2, 3 provide for vertical upward and downward movement of the seat ~rame 6, the back rest 11 can be mounted directly on the seat frame 6 to achieve its desired upward and downward movement at a con-stant inclination to the vertical.
Since however the seat rest 10 supports the thigh 7, it is required, in accordance with the invention that the seat rest shall be supported at at least two of the points I7 1 to I7 6~ Since I7 1 is close to the knee axis IC this is an inconvenient centre at which to actually support the seat rest.
Among the most convenient instantaneous centres Eor this purpose are I7 2' I7 3 and I7.6-The support between the thigh 7 and link 2 is providedby a pivotal connection 20 at I7 2 between the seat pan 12 and link 2. Since however I7 3 is at a relatively long distance from the seat~ pivotal movement of the seat pan 12 about I7 3 is simulated by mounting a plate 21 on link 3, the plate 21 being part cylindrical about a horizontal axis through I7 3, and mounting a roller 22 on seat pan 12 to roll on plate 21, An even more convenient pair of centres are I7 2 and I7 6 Mounting of the seat pan for movement about I7 6 is simulated, as seen in the fragmentary illustration in Fig. 2A, by causing roller 22 to roll on a plate 23 fixed directly to the seat frame 6 and curved about the horiæontal axis through I7 ~.
Alternatively, the seat pan 12 could be positively supported on the transverse horizontal axis through I7 ~ by providing arms (as in Figs. 6 and 10) connec-ted to and projecting from seat frame 6 and seat pan 12 alongside the seat occupant, the respective arms being interconnected by pivots on the said transverse axis through I7 6. The connections from the arms to the seat frame 6 and seat pan 12 will be such as to support the seat pan on the seat frame.
The manner in which the seat rest moves when supported at I7 2 and I7 3 is illustrated in Fig. 3, the Eull line of the seat part correspondlng to the mid-ride position, and the UP- and DOWN-stop positions being shown in chain-dotted lines.
In the description which follows,reference n~tmerals 1 to 8 will be retained so far as possible to represent the same type of parts shown in Figure 2 in spite of minor variations in the shape and function of the parts, in order to avoid the confusion which would occur from the adoption of different references. References 2 and 3 wlll denote any two links by means of which the seat part is mounted on the base part.
Thus in Figure 4 there is shown,in skeleton form, a - l4 -~ 5~ 66~

type B suspension in which the back rest 11 is guided for vertical movement by sliding on a vertical rod la forming part of the base part I9 and the seat rest 10 is supported by links 2 and 3 of a modified type A suspension. Since the links 2 and 3 are no longer required to maintain the vertical movement of the seat, the type A suspension has been modified by omitting the lower rearward half of link 2 Alternatively the link 3 could hav~ been omitted, (as in Fig. 8). The seat rest 10 in this case is supported, as in Fig. 2 ~, at the instantaneous centres of rotation I7 2 and I7 6.
Figure S illustrates a modification of the seat suspen-sion of Figure 4 in that the type B suspension has been replaced by a type C suspension. In this case, the links of the modified type A suspension on which the seat rest is supported are indicated by re~erences 2A, 3A. The linlcs of the type C
suspension by which the seat frame 6 is mounted on the base l are indicated by references 2C and 3C.
Figure 6 shows in skele~on form a modified type A
suspension on which the seat part 10 is supported at instan-taneous centres of rotation I7 5 and I7 6. The support at I7 5 is achieved by providing a rigid link 30 connecting slider or roller 5 to a slider or roller 31 movable in a horizontal guide on the seat frame 6 and a part 30a upstanding from link 30 having a pivotal and sliding connection at point I7 5 :`
~ '`' ' ' ' .~;

~59L~i63 to the seat part 10~ A rigid link 32 rigidly connected to the seat frame 6 extends therefrom to a pivot connection 33 on an upstanding side member lOa of the seat part 10 at I7 6. Alter-natively, instead of allowing link 30a to slide relative to pivot 34, the link 32 coul~ be pivoted to seat frame 6 instead of being rigidly fixed. As shown a type B suspension is used to maintain the vertical movement of the seat frame 6. Alternatively, the vertical movement could be achieved by converting the modified type A suspension, on which the seat part 10 is supported, to a full type A suspension.
Figure 7 is a diagrammatic view, in skeleton form, of a modified type A suspension supporting a seat rest 10, with a type B suspe~sion supporting the back rest, and in which the seat rest 10 is pivoted at I7 2 and I7 5. ~he pivot connection at I7 2 is achieved as shown in Fig. 2. The I7 5 connection however is provided by a rigid link 40 connected between slider or roller 5 and a slider or roller 41 both moving in horizontal guides on frame 6, with a link ~2, pivotally connected to and upstanding from link 40, the link 42 having a pivotal connec-tion 43 to the seat rest 10 at I7 5.
As an alternative to the modified type A suspension as shown, one could us~ a different modified type A suspension, for example as in Fig. 6. A full type A suspension could be used for controlling the movement of the back rest.
Figure 8 is a representation9 in skeleton form, of a modified type A suspension on which the seat rest 10 is supported at I7 2~

~5~66 as described in connection with the embodiment of Fig. 7, andat I7 6 as described in connection with the embodiment of Fig. 6.
Figure 9 i9 a representation, in skel.eton form, of a seat part 10 supported a~ I7 6 as in Figure 8, and also at I7 1 In view of the difficulty of providing actual support at the point I7 1' the desired effect is achieved by pivotally connecting first and second rods 45, 46, at one end thereof to base part 1 and at their opposite end to a coupling rod 47 such that, as the system of rod 45-47 is moved pivotally a point on the rod 47 moves along an arc of a circle centred at point I7 1 An arm 48 rigidly fixed to the underside of the seat part 10 has a pivotal connection 49 to the above mentioned point on rod 47 so that pivotal connection 49 moves instan taneously about centre I7 Figure 10 is a representation, in skeletob form, of a seat part lO supported at I7 6 ànd at I7 1 by means different from those sho~n in Figure 9. In the present case, the support at I7 6 differs from that of Figure 9 in that a swinging link 50 depends from pivot connection 33 to a pivot connection 51 on the seat part 10. The support at I7 1 is provided by an assymetric scissor-action linlcage in which iinks 52, 53 of the linkage have roller connections 54, 55 on the base 1 and seat part 10 respectively, and fixed pivot connections 56, 57 on the seat part 10 and base part 1 respectively.

, ~59L66~

Figure 11 is a representation, in skeleton form, oE a seat part 10 supported at I7 6 as in Figures 8 and 9, and at I7 1 In this case, the support at I7 1 is provided by an arm 60 rigidly fixed to the seat part 10 and carrying a roller 61 at its lower end, the roller rolling on a part-cyclindrical sur~ace lb on base 1, the surface lb being arcuate about a horizontal axis through I7 l Figure 12 shows diagrammatically a type C suspension on which a seat -frame 6 i9 supported ~or vertical movement relative to a base 1 by two parallel links 2, 3 pivoted at their opposite ends to frame 6 and base 1. By the same method as was used in relation to Figure 1, the instantaneous centres of rotation of the thigh 7 of the seat occupant to parts 1, 2 and 6 have been plotted to provide four centres I7 1' I7 2' I7 3 and I7 6 at any two of which a seat rest could be pivoted .

Figure 13 shows diagrammatically a type C suspension in accordance with the teaching5 o~ Figure 12, in which an arm 65 ~1~ii4~i3 upstanding from link 3 has a pivo-tal connection 66 at I7 3 with the seat part 10. A further arm 67 upstanding from link 2 has a pivotal connec-tion 68 at I7 2 with the seat part lOo The pivotal connection 66 (as shown) or 68 may need to be received in a slot in the associated arm to permit some freedom for relative translational movement.between connections 66 and 68.
If the two instantaneous centres of rotation selected as pivot axes of the seat rest do not at all times provide stable support for the seat rest, the latter can be supported at one or more further instantaneous centres of rotation.
For example, two separate arcuate surface and roller connections at the front and rear of the seat part could be provided to permit rotation of the seat part about centre I7 6.
A closely related invention is disclosed and claimed in applicant's copending Canadian P~atent Application serial no. 347,272, filed March 7 r 1980 .
The description and teaching oE the invention given above will enable those skilled in the art to devise many other alternative embodiments within the scope of the invention~ and these various supporting means can be combined together in many different ways which will equally be apparent to those skilled in the art.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A suspended vehicle seat for providing isolation from vertical vibrations to an occupant thereof comprising a seat part, which includes a seat rest (10) which is mounted for tilting movement and a back rest (11), a base part (1), and means connecting the seat part to the base part, said means comprising a spring suspension by which the back rest is supported on the base part and which is effective to restrict movement of the back rest to a substantially vertical direction, the suspension including a spring and a plurality of relatively movable structural elements, certain of said elements connecting to the seat rest and to the back rest for providing pivotal movement of the seat rest about at least two spaced apart horizontal transverse axes through instantaneous centers of rotation, said centers being the instantaneous centers of rotation of the thigh (7) of a seat occupant for whom the seat is designed which is positioned on the seat rest relative to any two of said structural elements of the seat which move relative to each other during upward and downward movement of the seat part relative to the base part, said pivotal movement of the seat rest causing the thigh of a seat occupant to remain in contact with the seat rest and to be movable longitudinally and pivotally in such a way that the ankle hinge axis of the seat occupant will remain stationary relative to the base part as the seat moves above and below its mid-ride position in response to vertical vibrations.

2. A vehicle seat according to claim 1 wherein the seat part includes a seat frame (6), the back rest being mounted on the seat frame, and the elements connecting the seat frame (6) to the base part (1) comprise a pair of pivotally-interconnected links (2, 3) of which link (2) has a displaceable connection (5) with the seat frame and link (3) has a displaceable connection (4) with the base part, one of said links extending between and being pivotally connected at its opposite ends to the seat frame and the base part, one of said connec-tions being said displaceable connection, and wherein the means connecting said seat rest to said back rest permit rotation of the seat rest about one of the following pairs of instantaneous centres, namely I7.1 and I7.2, I7.2 and I7.3, I7.3 and I7.4, I7.1 and I7.3, I7.2 and I7.4, I7.3 and I7.5, I7.1 and I7.4, I7.2 and I7.5, I7.3 and I7.6, I7.1 and I7.5, I7.2 and I7.6, I7.4 and I7.5, I7.1 and I7.6, I7.4 and I7.6, or I7.5 and I7.6

3. A vehicle seat according to claim 2 wherein both of said links extend between said seat frame and base part and form the means whereby the back rest is guided for vertical movement.

4. A vehicle seat according to claim 2 or claim 3 wherein, for rotation or the seat rest about centre I7.6 or I7.3, a roller is mounted on said seat rest,a cam surface is mounted on seat frame (6) or link (3) and is arcuate about the respective centre, and said roller engages said cam surface.

5. A vehicle seat according to claim 1 wherein the seat part includes a seat frame (6) the back rest being mounted on said seat frame (6), and the elements connecting the seat frame (6) to the base part (1) include a link (for example 2) extend-ing between and being pivotally connected at its opposite ends to the seat frame (6) and the base part (1), one of said connections being a roller or slider connection (4 or 5),and wherein the elements connecting said seat rest to said back rest permit rotation of the seat rest about one of the following pairs of instantaneous centres, namely:
I7.1 and I7.2 I7.2 and I7.4 I7.4 and I7.5 I7.1 and I7.4 I7.2 and I7.5 I7.4 and I7.6 I7.1 and I7.5 I7.2 and I7.6 I7.5 and I7.6 I7.1 and I7.6

6. A vehicle seat according to claim 2, having a pivotal connection between the seat rest (10) and a member rigid with link (2) which permits rotation of the seat rest about centre I7.2.

7. A vehicle seat according to claim 2 wherein said displaceable connection compares a roller or slider (5), and a link is pivoted at its opposite ends to the seat rest and to the roller or slider (5), which permits rotation of the seat rest about centre I7.5.

8. A vehicle seat according to claim 2 having links upstanding from the seat rest, links projecting upwardly from said seat frame or forwardly from the back rest and means pivoting said upstanding links to said upwardly projecting links, whereby rotation of the seat rest about centre I7.6 is permitted.

9. A vehicle seat according to claim 2 having a rigid coupling rigidly connected to the seat rest adjacent the front thereof and a cam and roller connection or a system of pivoted linkages connecting said rigid coupling to the base part (1),the centre of the cam surface, or the instantaneous centre of rotation of a link of said system to which the coupling is pivoted, being at the point I7.1, whereby rotation of the seat rest about centre I7.1 is permitted.

10. A vehicle seat according to claim 1 wherein, the seat rest is pivotally supported on a further horizontal transverse axis through a third of said instantaneous centres of rotation when said two transverse axes do not positively locate the seat rest.