GB2150824A - Lumbar adjustment mechanism - Google Patents

Abstract

Adjustment mechanism for actuating an angularly displaceable lumbar support element acting on the upholstery of a vehicle or other seat backrest in a lumbar region thereof comprises a manually rotatable input shaft 20 acting through a spring type clutch 24 to drive a pinion 26 meshed with a toothed sector 12 which is coupled to the support element. The clutch has a fixed outer housing 28 within which is a coil spring which is radially expanded to brake the input shaft and resist movement of the support element other than when the input shaft is being rotated, the latter contracting the spring to allow free movement for adjustment of the support. <IMAGE>

Description

SPECIFICATION Lumbar adjustment mechanism This invention relates to an adjustment mechanism for use in varying the degree of lumbar support provided by an upholstered seat backrest.

The invention is particularly concerned with the type of lumbar adjustment mechanism in which a support element extends transversely across the backrest and includes a portion which bears directly or indirectly against the upholstery so that angular adjustment of the support element varies the support of the upholstery in the lumbar region of the backrest.

The object of the present invention is to provide an adjustment mechanism of the kind referred to including a compact drive transmission for effecting infinitely variable adjustment of the support element with a smooth action.

According to the present invention there is provided a lumbar adjustment mechanism of the kind referred to comprising a drive input member which is drivingly connected to said support element through the agency of a clutch device and gearing, said clutch device being operable automatically on the one hand to transmit rotary drive from the input member to the support element in response to the application of rotary drive to said input member and, on the other hand, to brake the gearing in the absence of drive input to the input member.

Preferably the brake device is of the known spring-clutch type in which a coil spring is expanded radially into frictional contact with a stationary housing to provide a braking action when drive transmission from output to input is attempted and is contracted radially out of frictional contact with the housing when drive transmission is applied via the input.

The gearing conveniently comprises a toothed sector and a meshing pinion, the pinion being connected to the output side of the clutch device and the sector being mounted for pivotal movement with the support element connected thereto so that pivotal movement of the sector results in displacement of the support element in a fore and aft direction relative to the seat.

In one convenient embodiment, the gear sector and the clutch device are carried by a common mounting plate formed integrally with a depressed portion in which the pinion is accommodated, the depressed portion having a mouth through which the gear sector extends for mesh with the pinion. In this manner, the position of mesh between the pinion and the gear sector can be enclosed between the clutch housing and the depressed portion of the mounting plate thereby achieving a compact structure involving only relatively small number of components. The mouth of the depressed portion advantageously forms a guide surface for maintaining proper mesh between the gear sector and the pinion.

One embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure lisa schematic view of the adjustment mechanism; and Figure 2 is an end view of the mechanism shown in Figure 1.

As shown, the adjustment mechanism comprises a mounting plate 10 which, in use, will be attached to or form part of one side of a vehicle seat backrest.

The plate 10 mounts a toothed gear sector 12 for angular movement about a pivot axis 14. A yoke 16 is angularly fast with the sector 12 and is formed with apertures 18 into which one of the bent ends of a support element (not shown) can be inserted. The other bent end of the support element may be inserted into a similarly pivotally mounted yoke at the other side of the backrest so that the support element spans the width of the backrest.

The transverse length of the support element (or one or more portions thereof) may directly or indirectly bear against the interior of the upholstery at the front of the backrest, in the lumbar support area, so that as the support element turns angularly about the pivot axes of the yoke 16, the upholstery in this region is displaced forwardly to a greater or lesser extent.

Such angular movement of the support element is effected by means of an input shaft 20 to the squared end 22 of which a user operable knob (not shown) or the like may be attached so that the knob is accessible to the seat occupant at the side of the backrest. The input shaft 20 is drivingly connected to the sector 12 by means of a spring type clutch 24 and a pinion 26 which meshes with the teeth 27 on the upper edge of the sector 12. As previously mentioned, the clutch 24 permits transmission of rotary drive from the shaft 20 to the pinion 26 but acts as a brake whenever transmission in the reverse direction tends to occur, e.g. due to loading of the support element.

The clutch housing 28 is fastened to the outer face 30 of the mounting plate 10 by means of flange 31 so as to cover a generally circular depressed portion 32 formed integrally with the plate 10. The space enclosed between the depressed portion 32 and the clutch housing 28 accommodates the pinion 26 and a cutaway area 34 (which facilitates formation of the depressed portion 32) in the plate 10 provides a mouth through which the upper end of the sector enters for meshing engagement with the pinion.

The depressed portion 32 in the region of the cutaway 34 is formed with a guide surface 36 which together with the pressed out portion 38 below the cutaway portion guides and thereby maintains the sector 12 in proper registry with the pinion.

From the foregoing, it will be understood that rotation of the input shaft 20 in either sense is transmitted to the pinion 26 via the clutch device 24 and, in turn, displaces the sector 12 about the axis 14 between the limits defined by stops 40. In this manner, the support element can be adjusted by the seat occupant in order to afford greater or lesser lumbar support. When the actuating knob is released, the support element will remain in the position of adjustment even though subjected to loading by the occupant because drive transmission from output to input is prevented by the clutch device 24.

It will be noted that the illustrated embodiment results in simplification of the manufacture and assembly of the mechanism since all of the components are mounted on a single plate and it also provides infinitely variable adjustability, low operating loads and a smooth action during adjustment.

Claims (10)

1. Lumbar adjustment mechanism for a seat backrest including a support element extending transversely across the backrest, a portion or portions of which bear directly or indirectly against upholstery of the backrest in use so that angular adjustment of said element varies the support of the upholstery in a lumbar region of the backrest; said mechanism comprising a drive input member, a drive output member for causing said angular displacement of the support element, and drive transmission means drivingly connecting said input and output members comprising a clutch device operable automatically on the one hand to transmit rotary drive from the input member to the output member in response to rotation of the input member and, on the other hand, to brake the output member in the absence of rotary drive input to the input member.

2. Mechanism as in Claim 1 wherein the clutch device includes an operatively stationary housing and a coil spring within the housing which is expanded radially into frictional engagement with the housing to brake the output member when drive transmission from the latter to the input member is attempted but is contracted radially out of frictional engagement with the housing when drive transmission is applied from the input member to the output member.

3. Mechanism as in Claim 1 or 2 wherein the drive transmission means comprises a pinion on the output from the clutch device and a toothed sector meshing with the pinion and mounted for pivotal movement of the support element.

4. Mechanism as in Claim 3 wherein the clutch device and the toothed sector are carried by a common mounting plate which, in use, is attached to or forms part of the backrest.

5. Mechanism as in Claim 4 wherein the mounting plate has an integral depressed portion in which the pinion is accommodated, said depressed portion defining a mouth through which the gear sector extends to mesh with the pinion.

6. Mechanism as in Claim 5 wherein said mouth includes a guide surface which in conjunction with another portion of the plate guides the sector in register with the pinion.

7. Mechanism as in any preceding claim wherein the input member is a shaft on which the clutch device acts directly, and which mounts a user operable knob for rotation thereof in use.

8. Lumbar adjustment mechanism substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

9. A seat backrest including a lumbar adjustment mechanism as in any preceding claim.

10. A seat for a vehicle including a backrest as in Claim 9.