Technical Field

The present invention relates to seat height adjusters. Background

A known seat height adjuster comprises a catch mechanism, comprising a rack of teeth, which serves to receive a latch member and so maintain a seat supported thereby at a chosen height. It has be found that, over a long period of time, in changing the height of the seat the latch member, in moving from one position in the teeth to another position so as to change the height setting, the catch mechanism is degraded due to excessive force and wear. This results in the catch mechanism not being as effective at maintaining the latch member in position. Unable to maintain the latch in particular position, due to the weight of a user, the adjuster will fail and the seat will drop downwards in an uncontrolled manner, potentially resulting in injury to the user. Where the user is driving a vehicle at the time, the failure may result in the user losing control of the vehicle.

We seek to provide an improved seat height adjuster. Summary

According to a first aspect of the invention there is provided a seat height adjuster comprising a support to support a seat, a threaded member, a pivotably mounted guide arm assembly, a guide member connected to the guide arm assembly, and the guide member connected to the threaded member so as to translate the guide member along the threaded member on rotation of the threaded member and thereby pivot the guide arm assembly so as to adjust a height setting of the support, and wherein the adjuster comprises two threaded members, and each threaded member connected to a respective handle assembly, each handle assembly operable to adjust the height of forward and rearward ends of the support respectively, and the handle assemblies located at respective sides of the height adjuster, or on the same side of the height adjuster. Brief Description of the Drawings

Various embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of a seat height adjuster, and

Figure 2 shows a perspective view of a handle assembly of the seat height adjuster of Figure 1.

Detailed Description

With reference to Figure 1 there is shown a seat height adjuster 1 for a vehicle driver seat comprising a support frame 3 , the height setting of which is adjustable. The support frame 3 is provided on its uppermost surface with two support members 3a which are provided with apertures 3b. The apertures 3b allow a seat, not illustrated, to be attached to the support members 3a by way of suitable fastening devices.

The seat height adjuster 1 further comprises a base structure 5 , which is arranged to be attached to a floor. The base structure 5 comprises two members 5a and 5b. Two apertures provided in each of the members 5a and 5b, provide for pivotable mounting of a guide arm assembly. The guide arm assembly, which essentially forms a scissor arm assembly, comprises four guide arms. Two guide arms 10a and 10b are provided at the forward end of the seat height adjuster, whereas two guide arms 11a and l ib are provided at the rearward end of the seat height adjuster. The guide arms 11a and lib are attached to a guide member 12. A first distal end portion of the guide member 12 is arranged to be received in a guide slot 20. An opposite distal end of the guide member 12 comprises a threaded bore arranged to threadibly engage with an elongate threaded member 25 in the form of a threaded rod. As shown in broken lines, a portion of the guide member 12 adjacent to the threaded bore is received in a further slot 20, and provided in an opposite support frame member. A distal end of the threaded member is received and held in an aperture provided in a bracket 18. Attached to each of the guide arms there is provided a spring biasing arrangement comprising an arm 30a, a mounting pin 30b extending from said arm and a torsion spring 30c mounted on the pin. The arm 30a is fixedly attached to the support frame 3 and one end of the torsion spring is held captive in a slot in the pin and the other end of the spring is connected to the guide arm lib.

The arrangement of the (forward end) guide arms 10a and 10b is very similar to that of the guide arms 11a and lib. The forward end guide arms 10a and 10b are attached to a guide member 15. A first distal end of the guide member comprises a threaded bore which threadibly engages with a threaded member 26. An opposite distal end of the guide member 15 is received in a slot 21. A corresponding slot, shown in broken lines, receives a portion of the guide member 15 intermediate of the distal ends. The guide arms 10 and 10b are provided with respective spring biasing arrangements, essentially identical to the spring-biasing arrangement described above. A distal end of the threaded member 26 is held in an aperture of a bracket 19.

The height adjuster 1 further comprises two handle assemblies 40 and 50 for manually driving the threaded members 25 and 26 respectively. Reference is now made to Figure 2 which shows the handle assembly 40 in more detail. It will be appreciated that the handle assembly 40 is very similar to the handle assembly 50. The handle assembly 40 is attached to the support frame by two fasteners 47 (as best seen in Figure 1) and two fasteners 48. Advantageously, a flange 49 is provided with an aperture which is aligned with the aperture 3b of the member 3a, through which a fastener for the seat is located. In the event that both fasteners 47 and 48 fail, this fastening point will hold the handle assembly in location.

The handle assembly 40 comprises a rotatable handle 41 , a shaft 42 connected to the handle, a gear assembly 43 and a sleeve 44. The sleeve 44 is fixedly attached to the threaded member 25. The gear assembly 43 comprises a bevel gear arrangement, preferably having a 2: 1 gear ratio. Advantageously, the handle assemblies are ergonomically positioned, at the front right and left of the seat. In use the seat height adjuster 1 operates as follows. Should a user wish to adjust the height of the rear of the seat he can operate the handle assembly by rotating the handle 41. In so doing, since the threaded member 25 is fixed from translational movement, the guide member 12 will be forced to translate within the slots 20. This causes the guide arms 11a to pivot and thus adjust the height of the rearward end of the seat. The same operating principles apply to height adjustment of the forward end of the seat using the handle assembly 50. The ability to adjust the forward and rearward ends independently of each other advantageously allows the user to achieve a height setting in which the seat is titled with a chosen attitude. Should the user wish to raise the height of the seat, the spring biasing arrangements advantageously act to force the respective guide arms upwardly (so easing the seat raising procedure for the user) . Because maintenance of a particular height setting is achieved through the frictional engagement between the threaded member and the guide member, failure of the adjuster is extremely unlikely, and accordingly the seat height adjuster is substantially failsafe. However, in the unlikely event of failure, any harm is minimised.

Furthermore, the seat height adjuster allows the user infinite adjustment (within the height range limited by the length of the slots 20 and 21) , instead of adjust to discrete positions only.

It will be appreciated that an alternative embodiment is not arranged to allow independent adjustment of the height the forward and rearward ends is possible. Rather, inclusion of similar guide arm, guide member and threaded member arrangement as described above allows height of the support frame at a preset attitude (eg a horizontal attitude) .

In another embodiment, instead of the threaded members and handles being provided on different sides , both handles and threaded members are provided on the same side.

It will further be appreciated that the seat height adjuster finds particular utility for use with seats of vehicles , and in particular vehicle driver seats , which operate in harsh vehicle environments such as buses , trains, military vehicles and construction vehicles.

Various further advantages of the height adjuster include:

Reduced reliance on welded assemblies

Controlled decent and accent

Quick and easily to adjust, whilst the user is sitting on the seat

Easily serviced, with components such as the threaded members being easily viewable and accessible externally Cost reduction Weight reduction