Seat arrangements providing adjustable lumbar support

Chairs and seats – Bottom or back with means to alter contour – Providing support for lower back region

Patent

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Details

2972847, A47C 300, A47C 2500

Patent

active

054492190

DESCRIPTION:

BRIEF SUMMARY
This invention concerns improvements in and relating to seat arrangements providing adjustable lumbar support, and more especially to a seat structure that is particularly adapted for use in an automobile seat of the kind wherein a platform element providing support for the upholstery of the seat is resiliently suspended in a seat frame.
It is known, see for example EP 0 169 293, that an assembly for incorporation in a seat back to provide adjustable lumbar support may comprise a platform element adapted to be suspended in a seat frame to support the cushioning of a back rest, said platform element including two elongate lateral rails between which extend transverse members that provide the platform support, adjustable means being linked between respective portions of each of said elongate rails to apply thereto a force of longitudinal compression, whereby said rails are caused to be arched outwardly in the lumbar region of the back rest together with the transverse members carried thereby.
Such an arrangement provides an adjustable and comfortable lumbar support which is of relatively simple design. It has the disadvantage, however, that the outward arching of the lumbar region of the back rest is required to be caused by flexing of the elongate lateral rails, which are of spring wire construction and must be of relatively heavy gauge to support the bending forces applied thereto by tension springs supporting the arrangement in the seat frame and which are required to carry load placed upon the platform element. Thus a relatively high force of longitudinal compression is required to cause the arching of the lateral rails, particularly when the platform element is providing minimum lumbar support and is in a relatively flat condition. Correspondingly heavy forces are thus placed upon the adjusting arrangement, which must be linked between the extreme ends of the lateral rails to give the maximum mechanical advantage in applying a bending force to the rails. The places a limitation upon the available types of adjusting mechanism that can be used, as well as requiring a significant space for the adjusting arrangement within the back rest itself.
It also has the further disadvantage, however, that although the degree of lumbar support can be readily adjusted in the horizontal direction, the vertical position at which lumbar support is provided is determined by the initial geometrical shape of the platform element and the points at which the compression forces are applied to the lateral rails, so that it is impossible for an occupant of the seat to adjust the lumbar support in a vertical direction to meet individual requirements.
Other known systems are available to provide for vertical adjustment of lumbar support, but these have the disadvantage that they are not adaptable to the particular arrangement initially referred to. Also, such known systems require that a support element scuff up and down on the back of the cushioning of the back rest, so that some form of additional sliding interface is necessary to allow free movement of the vertically adjustable support means.
It is a general object of the invention to provide an improvement on an assembly of the kind initially referred to.
It is a preferred object of the invention to overcome, or at least reduce one or more of the above mentioned disadvantages.
In accordance with one aspect of the invention, this object is achieved in that the said lateral rails are provided with a hinged articulation point in the region of lumbar support, whereby outward arching of the rails is effected by bending of the platform element in the form of a ridge.
Surprisingly, it has been found that despite the fact that the outward arching of the platform element forms a ridge or apex of increasingly acute angle, this does not, as might be expected, cause discomfort to the occupant of the seat, provided that the contouring of the platform element and the cushioning supported thereby are appropriately adapted to their purpose.
Preferably the lateral rails are freely hinged togeth

REFERENCES:
patent: 3106423 (1963-10-01), Schwarz
patent: 4725095 (1988-02-01), Benson et al.
patent: 5026116 (1991-06-01), Dal Monte
patent: 5197780 (1993-03-01), Coughlin

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