GB2349077A - Vehicle seat height adjustment mechanism. - Google Patents

Abstract

A vehicle seat height adjustment mechanism 12 comprises a ratchet and pawl mechanism 18 for raising the seat and a damper 20 to provide smooth lowering of the seat. In the preferred embodiment, a lever 22 is provided which operates a ratchet wheel (27, Fig. 2) to raise the height of the seat when moved in a first direction. Movement of the lever in a second direction disengages the pawls (24, 26, Fig. 2) so that the seat moves smoothly downward under the weight of a user against the action of a gas spring 20.

Description

AUTOMOTIVE SEAT MECHANISMS This invention relates to automotive seat mechanisms and more particularly to systems for raising or lowering automotive seats in a controlled manner.

Various mechanisms for adjusting the height of vehicle seats are generally known. In particular GB 1,491,292 describes one such arrangement in which the seat is supported via a scissors type understructure. The angles of the arms of the scissor structure are varied in order to alter the seat height. An adjusting lever which incorporates a locking means is arranged to generally lock the angular position of the arms and so set the seat height. In addition resilient supports are provided to generally cushion the seat and allow it to move slightly vertically about the set height with a springing action.

The level of springing action and resilience can be varied and adjusted in response to the load on the seat.

Another arrangement is described in GB 2,194,305 which although generally referred to as a mechanism for adjusting an armrest specifically also refers to using the mechanism for adjusting the height of a seat. Using this mechanism, a seat would be supported via a pair of swinging links which are arranged as a parallel linkage mechanism.

One end of each of the links attaches to the seat whilst the other end attaches to a slider. The links and slider are arranged such that moving the position of the slider causes the links to rotate and raise the height of the seat. As described a motor may be provided to move the slider in both directions, via a suitable rack and worm mechanism, to raise and lower the seat and lock its position. Alternatively a ratchet mechanism is provided to lock the position of the slider whilst springs or gas struts are provided to load and bias the mechanism such that when the locking mechanism is released the seat tends to rise. Lowering is then achieved by pressing downward on the seat.

A yet further proposed arrangement is described in DE 3,134,298. In this prior patent application a vehicle seat adjusting device is described as including a ratchet means which is arranged to raise and lower the seat position. The ratchet means is operated by a hand lever and includes a locking pawl which is thereby arranged to lock the position except when the ratchet means is engaged.

We have identified a need for improvements in the manner of raising and lowering automotive seats in order to provide improved flexibility of control in combination with user satisfaction and an object of the present invention is to provide improvements in one or more of these respects, or generally.

According to the invention there are provided mechanisms for automotive seat adjustment as defined in the accompanying claims.

In an embodiment of the invention there is provided a mechanism in which raising of the seat is provided in a direct and positive manner by actuation of a mechanical mechanism, and lowering of the seat is provided by simple and direct actuation of a mechanism which permits cushioned lowering of the seat.

In the embodiment these functions are provided in a simple and cost-effective manner by the use of simple mechanical expedients such as pawls and ratchets in combination with corresponding cost effective cushioning means such as fluid damper units.

An aspect of an embodiment of the present invention provides an automotive seat adjustment mechanism comprising a raising mechanism, locking means and a cushioned lowering mechanism. The raising mechanism is arranged in use and when operated to provide direct and positive motive force to raise the seat position. The cushioned lowering mechanism is arranged in use to provide cushioned lowering of the seat once actuated and the raising mechanism and locking means is disengaged. As such raising of and upwards movement of the seat is provided and controlled by the raising means whilst lowering of the seat is controlled and cushioned by the cushioned lowering mechanism. The locking means, which are preferably and most conveniently combined with the raising means then lock the desired position of the seat.

In some respects the seat mechanism operates in a manner comparable to that of a gas-assisted office chair in which a single lever provides both lift and a cushioned lowering facility. In the embodiments of the present invention, the lift facility is provided by an active ratchet-operated mechanism in contrast to the simple gasassisted mechanism of the office chair, which also offers the cushioned lowering facility.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig 1 shows a side elevation view of the seat and its associated adjustment mechanism; and Fig 2 shows on an enlarged scale, a sectioned side elevation view of the active-lift portion of the adjustment mechanism.

Referring to figure 1 an automotive seat 10 is mounted to the floor 2 of a vehicle via an adjustment mechanism 12 which in particular is arranged to raise and lower the position of the seat 10. It will be appreciated that a further mechanism (not shown) may also be provided or combined with the adjustment mechanism 12 to adjust the fore and aft position of the seat 10.

The adjustment mechanism 12 operates through and comprises a twin pair of seat lift/lowering arms 14,16, a lever operated ratchet mechanism 18 and a fluid damped cushioning device 20. Each pair of lift/lowering arms 14,16 are mounted on either lateral sides of the seat 10. One end of the each of the arms 14,16 is pivotally connected, via pivot pins 5 and 6, to the base of the seat 10. The other ends of each of the arms 14,16 are pivotally connected, via pivot pins 7 and 8, to a mounting frame 4 which is mounted to the floor 2 of the vehicle. The arms 14,16 are arranged generally parallel to each other and via the pivotal connections, mounting frame 4 and seat 10 operate as a parallel linkage mechanism such that pivotal rotation of one arm 14 (shown by arrow X) causes pivotal rotation of the other linkage 16 (shown by arrow Y) and vertical movement of the seat 10 (shown by arrow Z).

In this embodiment the front arms 14 and rear arms 16 are of generally the same length and are arranged generally parallel to each other so that as the seat 10 is raised and lowered its orientation is maintained and specifically the seat 10 is kept generally level. Alternatively the forward and rear arms 14, 16 could be of different lengths and/or set at an angle to each other in which case as the seat 10 is raised or lowered the orientation of the seat 10 would change. Specifically the seat 10 would tilt in a forward or rearward direction. Depending upon the particular vehicle and seat 10, such tilting may be beneficial.

The fluid damped cushioning device 20 comprises for example a fluid damped telescopic piston strut, gas spring, or similar. One end of the device 20 is pivotally connected to the upper seat end of the forward arm 14 via pivot pin 5. The other end of the cushioning device 20 is pivotally connected to the lower mounting frame end of the rear arm 16. The cushioning device 20 thereby extends generally longitudinally along the side of the seat 10 and forms a diagonal strut between the generally parallel arms 14,16.

As the arms 14,16 pivot and the seat 10 rises and falls the diagonal distance between the arms 14,16 and pivot pins 5 and 8 will vary and accordingly the fluid damped cushioning device 20 will be extended and contracted in response to this movement of the seat 10. It will be appreciated that the fluid damped cushioning device 20 could alternatively be mounted about the other diagonal between pins 6 and 7.

In such a case the device 20 would still extend and shorten as the seat 10 is moved up and down but this would be in the opposite sense to that produced with the arrangement shown in figure 1.

In figure 1 only one pair of arms 14,16 on one side of the seat 10 are shown. The pair of arms on the other side are arranged in a generally similar way but preferably in the interests of simplicity and economy excluding the lever operated ratchet mechanism 18 and fluid damped cushioning device 20. Of course if required to improve operation a second fluid damped cushioning device 20 could be provided with the other pair of arms on the other side of the seat 10.

The lever operated ratchet mechanism 18 is mounted to the mounting frame 4. This mechanism 18 is drivingly connected and coupled to one of the forward arms 14 via a sector pinion 30 which is provide on or coupled to the mounting frame end of the arm 14. Of course the lever operated ratchet mechanism could also be coupled to and arranged to drive, via a suitable shaft and further pinions, the forward arm on the other side although generally this is unnecessary and simply complicates the mechanism.

The lever operated ratchet mechanism 18 is shown in more detail in figure 2. The mechanism 18 comprises a housing 29, an operating lever, a ratchet wheel 27, associated driving and locking pawls 24,26, and a drive pinion 28. The drive pinion 28 meshes with the sector pinion 30 (as shown schematically in figure 2) thereby drivingly connecting the ratchet mechanism 18 to the forward arm 14. The ratchet wheel 27 and drive pinion 28 are coupled together and are rotatably mounted on a shaft 25 such that the ratchet wheel 27 and drive pinion 28 can rotate relative to the housing 29 and mounting frame 4. The operating lever 22 which extends generally horizontally is freely pivotally mounted at one end to the shaft 25 and can pivot relative to the shaft 25, the first pinion 28 and ratchet wheel 27.

A first pawl 24 is pivotally connected to the lever 22 via a pawl mounting pin 33 at one end of the pawl 24 and is arranged to engage and drive the ratchet wheel 27. A further pin 34 extends from the pawl 24 and is engaged within an associated arcuate guide slot 32 within the housing 29. This guide slot 32 and pin 34 controls the position of the pawl 24 and its engagement with the ratchet wheel 27. The second pawl 26 is pivotally mounted to the housing 29 via pin 35 and similarly is arranged to engage the ratchet wheel 27. Pawl biassing means (not shown), for example springs or the like, are provided to urge the pawls, and in particular the second locking pawl 26, into engagement with ratchet wheel 27 and drive teeth thereon.

Lever biassing means (not shown) are also provided to bias and maintain the lever 22 in a null position indicated by 31 which in this case is generally horizontal.

In use, manual actuation and raising of lever 22, as indicated by arrow A, from the generally horizontal null position 31, causes pawl 24 to engage and turn ratchet wheel 27 and the coupled first pinion 28, as shown by arrow E, in a generally anticlockwise direction. During the raising of the lever 22 the arcuate guide slot 32 and pin 34 controls the relative position of pawl 24 and urges and maintains it in engagement with the ratchet wheel 27. The rotation of the drive pinion 28 causes angular movement of the sector pinion 30 and corresponding angular pivotal movement of lift arm 14 about its pivotal mounting pin 7, as shown by arrow C. Such pivotal movement of the lift arm 14 causes similar angular pivotal movement of the other arms 16 and raises the seat 10. Pawl 26 prevents return rotation of wheel 27 and so lowering of the seat 10. As such the mechanism 18 and engagement of pawl 26 prevents the reverse, in this case clockwise, rotation of the ratchet wheel 27 and locks the position of the seat 10. The lever 22 can therefore be released and returned to the null position 31 with pawl 26 preventing reverse rotation of the wheel 27 and lowering of the seat 10. Further raising of the seat 10 can then be obtained by lifting the lever 22 again from the null position 31 as shown be arrow A. In this way the seat 10 can be raised and ratcheted, to a desired position, by repeated lifting of the lever 22.

Accordingly the lever operated ratchet mechanism 18 directly and positively drives the angular pivotal movement of the forward arm 14 thereby providing a means for raising and locking the position of the seat 10. An occupant of the seat 10 actively operates and repeatedly raises the lever 22 and lever operated ratchet mechanism 18 to drive and provide the motive force to raise the seat 10 position. As such the mechanism 18 provides an active and positive means for raising the position of the seat 10. The seat 10 occupant actively driving and providing the motive force to drive and raise the seat through the use of the mechanism 18 which raises the seat 10 in a controlled regulated manner. It will be appreciated though that other active raising means, including motorised means, could be used in place of the preferred above described lever operated ratchet mechanism 18.

To lower the seat 10 the lever 22 is moved downward, as shown by arrow B, from the null generally horizontal position 31. This moves the pawl 24 downwards, in a clockwise direction. By virtue of arcuate slot 32 and associated pin 34 this causes the pawl 24 to pivot away from the ratchet wheel 27 about pin 33 and disengages the pawl 24 from the ratchet wheel 27. Likewise locking pawl 26 is disengaged and pivoted away from the ratchet wheel 27 by a lever lug 35 on the lever 22 and associated pin 36 which abuts against the lug 35. With the both the pawls 24 and 26 disengaged from the ratchet wheel 27, the wheel 27 and drive pinion 28 are free to rotate. Sector pinion 30 and arm 14 is therefore free to rotate and pivot as shown by arrow D. Accordingly with the lever operated ratchet mechanism 18 disengaged, the seat 10 is free to descend and move down under the weight of the seat occupant and/or weight of the seat 10 with the arms 14,16 pivoting downwards.

The downward movement of the seat 10, and in particular the rate of movement, is however controlled and restricted by the fluid damped cushioning device 20 which, in the embodiment shown is extended as the seat is moved downward. The fluid damped cushioning device 20 being arranged to only extend at a certain rate and to resist being extended at a faster rate. In this way the seat 10 is lowered in a gentled and controlled manner. Since the lowering of the seat 10 is controlled by the fluid damper device 20 lowering of the seat 10 is also cushioned and the motion of the seat 10 is damped. Typically by using a suitable fluid damped cushioning device the seat is arranged to descend from its maximum to minimum height in about 4 seconds.

Once the seat 10 has been lowered to the desired position the lever 22 is released and/or returned to the null generally horizontal position 31. The pawls 24,26 will then re-engage and the lock movement of the ratchet wheel 27 thereby locking the position of the seat 10.

It will be appreciated that with this adjustment mechanism 12 the lowering of the seat 10 is substantially passive with the seat 10 simply descending under its own weight and/or the weight of the occupant. The occupant is not required to actively drive or apply a controlling force to lower and/or control the lowering of the seat 10. All that the occupant is required to do to lower the seat 10 is to activate the lever 22 until the desired lower seat 10 position is reached.

This arrangement provides a simple and cost effective vehicle seat adjustment mechanism for adjusting the height of a vehicle seat 10 which is easy to use. In this arrangement a single operating lever 22 which is simply raised or lowered, is used to raise and lower and lock the seat 10. This makes operating the adjustment mechanism simpler with an occupant not having to operate and find multiple switches or levers. The arrangement is also relatively small and since it is generally mounted to one side of the seat 10 the seat 10 can be mounted relatively close to the floor 2.

The arms 14,16 provide a simple, rugged and stable means for mounting the seat 10 and adjusting its height.

The adjustment mechanism is also easy to lower by virtue of the substantially passive lowering system generally requiring very little effort from the occupant and not requiring the occupant to control or actively drive the lowering of the seat. The provision of the fluid damper cushioning device 20 to control the lowering of the seat 10 also ensures that the seat 10 is gently lowered in a cushioned fashion which is desirable for an occupant.

The lever operated ratch arrangement 18 permits the seat 10 to be raised without requiring extensive movement of the lever 22. Consequently very little space is required around the lever 22 to allow for it to be operated and when the desired position is reached the lever 22 can be returned to a null position 31 out of the way of the occupant. Furthermore since little movement of the lever 22 is required the lever 22 can, if desired, be made longer to increase the mechanical advantage, so reducing the force that an occupant is required to exert in order to raise the seat 10. It being appreciated that with some other arrangement the required movement of the lever will restrict the length of an operating lever. The use of the ratchet mechanism 18 to not only raise the seat 10 but to also lock the seat 10 position simplifies the overall mechanism 12. Using this mechanism 18 the position of the seat 10 can also be set at a large number of varied positions as may be required by different occupants.

It will be appreciated that the arrangement and mechanism described above and in the figures is only an exemplary embodiment of the invention and that a number of variations are possible without departing from the scope of the invention.

Claims (11)

1. An automotive seat adjustment mechanism comprising a raising mechanism, locking means and a cushioned lowering mechanism, the raising mechanism is arranged in use and when operated to provide direct and positive motive force to raise the seat position, whilst the cushioned lowering mechanism is arranged in use to provide cushioned lowering of the seat once actuated and the raising mechanism and locking means is disengaged.

2. A mechanism according to claim 1 wherein a combined lockable raising means comprises said raising means and said locking means.

3. A mechanism according to claim 1 or claim 2 wherein said raising mechanism comprises a mechanicallyoperating pawl and ratchet mechanism.

4. A mechanism according to any preceding claim wherein said passive lowering means comprises a fluid damped cushioning device.

5. A mechanism according to claim 4 in which said fluid damped cushioning device comprises a gas spring.

6. A mechanism according to claim 4 or claim 5 in which said fluid damped cushioning device is telescopic and is arranged, in use, to extend and contract in a controlled manner as the seat is raised and lowered.

7. A mechanism according to claim 1 comprising a twin pair of pivotally mounted arms which mount and support the seat, and which are arranged such that in use pivotal angular movement of the arms raises the seat.

8. A mechanism according to claim 5 in which the raising means are coupled to drive angular pivotal movement of at least one of the arms.

9. An automotive seat adjustment mechanism comprising an active lift means and a passive lowering means in which the active lift means is arranged to provide, in use, a direct and positive motive force to raise the seat, and the passive lowering means is adapted such that when operated the seat will descend in a controlled cushioned manner substantially without any separate active motive force.

10. An automotive seat adjustment mechanism adapted to provide active lift and passive lower operating characteristics.

11. An automotive seat adjustment mechanism as hereinbefore described with reference to figures 1 and 2.