SEAT POSITIONING MECHANISM

Abstract: A seat height and tilt mechanism for a vehicle seat has separate hand wheel controlled adjusters for adjusting the seat height (62) and tilt (50). A control lever (38) can be moved relative to the seat base and a system of pivoted links then results in the seat as a whole being raised or lowered. The control lever can alternatively be locked relative to the seat base. When the control lever is so locked, the front edge of the seat can be lifted to tilt the seat.

Description: This invention relates to a seat positioning mechanism for adjusting both the height and the tilt of a seat in a motor vehicle. Although a number of highly sophisticated seat adjustment devices are known (see for example US-A-3 692 271), these have the disadvantage of overcomplexity, both in manufacture and assembly and in not being user-friendly. Positioning mechanisms powered by electric motors are also known and an example of such a mechanism is shown in US-A-4 632 353. US-A-4 529 159 on which the preamble to claim 1 is based discloses a seat positioning mechanism for a motor vehicle which allows adjustment of the seat height, comprising a system of pivoted links in the form of bell-cranks connecting the corners of the seat frame to ends of the seat slides, and an actuator which is operable to pivot the links. FR-A-2 503 061 discloses a seat positioning mechanism for a motor vehicle which allows adjustment of the seat tilt, comprising an axle mounted on a frame which is connected to the floor and engaging with a frame connected to the seat. Rotation of the axle alters the tilt of the seat. There is a need for a mechanism which allows adjustment of both seat height and seat tilt and which is of relatively simple construction which is robust, easy to operate and which is relatively cheap to manufacture and install. Further criteria are that the mechanism should not obstruct the space for the rear seat passengers feet under the front seat of the vehicle and that the mechanism should provide adequate rigidity to the seat mounting to prevent any adverse effect on the fore and aft sliding movement of the seat on its fixed slides. According to the invention, there is provided a seat positioning mechanism for a motor vehicle which allows adjustment of the seat height, the mechanism comprising a first frame to be attached to the underside of a seat cushion, a second frame to be mounted on seat slides fixed to the vehicle floor for fore and aft movement thereon, the first and second frames being four-sided frames each with two lateral members joined by two transverse members, a system of pivoted links inter-connecting the two frames at each corner, a first adjustment device for operating the seat height adjustment, one of the pivoted links being a control link which is mounted at the front of the mechanism and has a toothed quadrant pivoted to the first frame and engaging with a toothed pinion on the shaft of the first adjustment device with the quadrant being pivotable to alter the angle the link makes to the first frame, characterised in that the mechanism also allows adjustment of the seat tilt and includes an axle mounted on the second frame and operable to produce vertical movement of the axle relative to the second frame, with the control link and the other front link being pivotably mounted on the axle, and a second adjustment device for rotating the axle to operate the seat tilt adjustment. The adjustment devices are preferably manually operated hand wheels which act through clutch spring devices to prevent the associated shafts from turning except when the hand wheel is being turned. The pivoted links are preferably in the form of bell crank levers and the two levers on each side are connected to one another so that they make corresponding movements without any lost motion. Because the control link is mounted at the front of the mechanism, incorporates one of the pivoted links at one corner of the frames and has a toothed quadrant which meshes with a toothed pinion on the shaft of the first adjustment device, the action of turning the first adjustment device drives the quadrant and the control link so as to raise or lower the front of the first frame relative to the axle. Because the frames are connected by the pivoted links which are themselves interconnected, this results in the rear end of the first frame being raised or lowered an equivalent amount. The axle preferably carries toothed pinions which are rotated by the second adjustment device and which mesh with the teeth of racks which extend vertically. With the first adjustment device locked, movement of the second adjustment device to raise or lower the axle along the vertical rack results in raising or lowering of the front edge only of the first frame. In order to reduce the torque needed to raise the first frame with the seat, a spring arrangement can be fitted to urge the first frame in an upward direction. The spring arrangement can comprise for example a torsion bar or a coiled torsion spring. The invention will now be further described, by way of example, with reference to the accompanying drawing in which: Figure 1 is a perspective view of a positioning mechanism in accordance with the invention; and Figure 2 is a schematic drawing of part of a spring clutch for use in the invention. The mechanism shown in Figure 1 comprises a first frame 10 and a second frame 12. The first frame consists of two longitudinal members 13, 14 and two transverse members 16 and 18. The base of a seat will be mounted on this frame. The second frame consists of longitudinal members 20 and 22 joined by transverse members 24 and 26. The longitudinal members 20, 22 run on fixed tracks 28, 30 which are secured to the floor of the vehicle body, and the fore and aft sliding movement of the longitudinal members or runners 20, 22 on the tracks 28, 30 will be achieved in a conventional manner as already known to those skilled in the art. Pivoted bell crank levers 32, 34, 36 and 38 are mounted on the transverse bars 16, 18 of the first frame, and have one limb connected to a tie bar 40 or 42. The other limbs of the rear links 34, 36 are pivoted at 44 or 46 to the transverse member 26. The forward limbs of the front links 32, 38 are pivoted on an axle 48 which spans the front end of the mechanism. The tie bars 40, 42 interconnect the links in pairs so that movement undertaken by a front link is also transferred to the rear link. The axle 48 has a projecting shaft end 50 on which a hand wheel will be mounted, and a spring clutch 52 is also provided. This spring clutch will be described in more detail later. Two pinions 54 are fixed on the axle 48 and are axially located so that they mesh with corresponding vertically arranged racks 56. Rotation of the shaft end 50 will cause the pinions 54 to turn relative to the racks and thus to rise up or descend down the racks. The link 38 also forms a control link and is different from the other three links 32, 34, 36 in that it has a rearward extension which carries a toothed quadrant 58. This quadrant meshes with a toothed pinion 60 mounted on the end of a shaft 62. A spring clutch 64 (to be described later) is also fitted on this shaft. Rotation of the shaft 62 by a hand wheel which will be mounted on it turns the pinion 60 and causes the quadrant 58 to move up or down past the position of the pinion. In use, the shaft 62 is used to alter the height of the seat and the shaft 50 is used to alter the tilt by raising the front edge of the seat relative to the rear edge. Considering first the case when the shaft 50 alone is turned to lift the front end of the seat, the pinion 60 will not move and as a result the relative positions of the quadrant 58 and the longitudinal member 14 will remain constant and will form a rigid arm. Lifting of the axle 48 will then cause the first frame 10 to lift at its front edge, about the axis 44, 46. This is a tilting movement. On the other hand, when the shaft 62 is turned without the shaft 50 being turned, then the quadrant 58 will move relative to the longitudinal member 14 and the transverse member 16 will move up or down in an arc about the axis of the axle 48. The movement of the quadrant 50 will be transferred to the rear link 36 on the same side through the tie bar 40, and the links 32, 34 on the other side of the frame will follow this movement because of the rigidity of the frame 10. This is a movement which adjusts the height of the seat. A torsion bar spring 66 has its ends supported in the links 34, 36 and is braced against the transverse member 18 so as to assist upward movement of the seat against the weight of somebody sitting in the seat. A second spring assist unit 68 is provided on the far end of the axle 48 in the form of a coil spring which winds up as the axle is driven down the rack 56 and unwinds as the axle rides up. The spring clutches 52, 64 are of the type which lock up to resist undesired rotation. Clutches of this type are used, for example, in window lift mechanisms. They consist of a drum 70 (Figure 2) the internal circumferential surface of which provides a braking surface for a coil spring 72. In its normal condition the spring is compressed inside the drum and if released would want to increase its diameter. It therefore produces a frictional braking effect against the drum surface. The spring however has internally directed ends 74, 76 and the diameter of the spring is such that if these two ends are driven apart from one another in a circumferential direction, the consequent reduction in the spring diameter is sufficient to release the frictional engagement between the spring and the drum. The spindle 78 shown in Figure 2 is the extension of the shaft 50 or 62 inside the clutch. An arm 80 secured to the spindle 78 engages with the end 76 of the spring, and a corresponding feature (not shown) on the shaft to be driven engages on the spring end 74. There is also a driving connection (also not shown) between the spindle 78 and the shaft to be driven, and this driving connection has sufficient lost motion to allow the spring ends 74, 76 to be driven apart before the lost motion is fully taken up. Once the lost motion is taken up, driving will commence and the spring diameter will have been contracted sufficiently to release the clutch. However as soon as the shaft 50 or 62 (or the hand wheels on those shafts) are released, the spring 72 will once again expand to lock the spindle. In this way the shafts 50 or 62 can be turned to any desired position and then released whereupon they will lock. The mechanism shown is simple, rigid and spacesaving. Separate controls are provided for seat lift and seat tilt and the space at the underneath back of the seat is not obstructed to any great extent. As a result of the use of two full frames 10 and 12, a rigid structure is produced which will not be subject to distortion in use. Although the mechanism has been described for use with manual control and hand wheels which are turned by the seat occupant, it would equally be possible to use electric motors to rotate the shafts 50 and 62.

Claims: A seat positioning mechanism for a motor vehicle which allows adjustment of the seat height, the mechanism comprising a first frame (10) to be attached to the underside of a seat cushion, a second frame (12) to be mounted on seat slides (28, 30) fixed to the vehicle floor for fore and aft movement thereon, the first and second frames being four-sided frames each with two lateral members joined by two transverse members, a system of pivoted links (32, 34, 36, 38) inter-connecting the two frames at each corner, a first adjustment device (58, 60) for operating the seat height adjustment, one of the pivoted links (38) being a control link which is mounted at the front of the mechanism and has a toothed quadrant pivoted to the first frame (10) and engaging with a toothed pinion on the shaft of the first adjustment device (58, 60) with the quadrant being pivotable to alter the angle the link (38) makes to the first frame (10), characterised in that the mechanism also allows adjustment of the seat tilt and includes an axle (48) mounted on the second frame (12) and operable to produce vertical movement of the axle (48) relative to the second frame (12), with the control link (38) and the other front link (32) being pivotably mounted on the axle, and a second adjustment device (54, 56) for rotating the axle (48) to operate the seat tilt adjustment. A seat positioning mechanism as claimed in Claim 1, wherein the adjustment devices are manually operated hand wheels which act through clutch spring devices (64, 52) to prevent the associated shafts from turning except when the hand wheel is being turned. A seat positioning mechanism as claimed in Claim 1 or Claim 2, wherein the pivoted links (32, 34, 36, 38) are in the form of bell crank levers and the two levers on each side are connected to one another so that they make corresponding movements without any lost motion. A seat positioning mechanism as claimed in any preceding claim, wherein the axle (48) carries toothed pinions (54) which are rotated by the second adjustment device and which mesh with the teeth of racks (56) which extend vertically. A seat positioning mechanism as claimed in any preceding claim, wherein a spring arrangement (66) is fitted to urge the first frame in an upward direction. A seat positioning mechanism as claimed in Claim 5, wherein the spring comprises a torsion bar (66).

Inventors: EASTER, ROBERT LESLIE
Applicants: FORD FRANCE S. A., FORD MOTOR COMPANY, FORD MOTOR COMPANY LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1989
Main classification: B60N2
IPC codes: B60N2