EP0026668A2 — Seat backrest having an adjustable lumbar support

Claim 1

Independent Claim 256 words

A seat backrest having a rigid back portion (10,114) and a resilient upholstered seatback cushion member (52,170) attached to said back portion, a generally horizontal lumbar pad (24,122) located between said back portion (10,114) and said cushion (52,170), said pad (24,122) being resiliently biased toward said rigid back portion (10,114) by said resilient cushion (52,170) and being mounted to be moved away from the back portion (10.114) to adjust the degree of lumbar support provided to an occupant in the seat, characterised in that said pad (24,122) is pivotally mounted to the outer end of a pair of divergent horizontally spaced link members (30,124); each of said spaced link members (30,124) being supported at its inner end for pivotal movement about a pair of vertically spaced trunnions (32',32", 136) located on each of a pair of threaded adjusting nuts (32,140); an adjusting screw (36,126) having a left-handed thread portion in engagement with one of said adjusting nuts and a right-handed thread portion in engagement with the other of said adjusting nuts; spaced bearing means (38' 160, 166) for rotationally mounting said adjusting screw (36,126) relative to said back portion (10,114); means on said screw (44,178) for limiting axial motion of said screw (36,126) relative to said bearing means (38', 160, 166); and a control means (40,128) on said screw (36,126) for rotating said screw to cause said adjusting nuts (32,140) to move toward or away from each other to cause said link members (30,124) to move, respectively, toward a retracted position or toward an extended position.

Claim 2

Dependent Claim 256 words

A seat backrest having a rigid back portion (10,114) and a resilient upholstered seatback cushion member (52,170) attached to said back portion, a generally horizontal lumbar pad (24,122) located between said back portion (10,114) and said cushion (52,170), said pad (24,122) being resiliently biased toward said rigid back portion (10,114) by said resilient cushion (52,170) and being mounted to be moved away from the back portion (10.114) to adjust the degree of lumbar support provided to an occupant in the seat, characterised in that said pad (24,122) is pivotally mounted to the outer end of a pair of divergent horizontally spaced link members (30,124); each of said spaced link members (30,124) being supported at its inner end for pivotal movement about a pair of vertically spaced trunnions (32',32", 136) located on each of a pair of threaded adjusting nuts (32,140); an adjusting screw (36,126) having a left-handed thread portion in engagement with one of said adjusting nuts and a right-handed thread portion in engagement with the other of said adjusting nuts; spaced bearing means (38' 160, 166) for rotationally mounting said adjusting screw (36,126) relative to said back portion (10,114); means on said screw (44,178) for limiting axial motion of said screw (36,126) relative to said bearing means (38', 160, 166); and a control means (40,128) on said screw (36,126) for rotating said screw to cause said adjusting nuts (32,140) to move toward or away from each other to cause said link members (30,124) to move, respectively, toward a retracted position or toward an extended position.

Claim 3

Dependent Claim 88 words

A seat backrest according to claim 1, characterised in that a second control means (130,148,150, 156,154,152) is mounted on said rigid back portion (114) for producing a limited degree of rotation of said adjusting nuts (140, 1401) about said adjusting shaft (126) and causing a corresponding pivotal movement of said link members (124) of said lumbar pad (122) so as to tilt said lumbar pad (122) and vary the vertical position of the forward-most portion (L,H,M) of its convex- shaped forward surface relative to the back portion (114).

Claim 4

Dependent Claim 103 words

A seat backrest according to claim 2, characterised in that, said second control means (130,152) includes a first member (146) which is fixed against axial movement but can rotate slightly about said adjusting shaft (126) and has slot portions (144) which engage one of the trunnions (136) on each adjusting nut (140,140'), said second control means further including a second member (152) which can move in a path parallel to the axis of said adjusting shaft (126), and cooperating means (148,150) on said first and second members for causing said first member (146) to rotate when said second member (152) is moved longitudinally.

Claim 5

Dependent Claim 43 words

A seat backrest according to claim 2 or claim 3, characterised in that said cooperating means includes a pin (148) fixed to one of said first and second members and an angled slot (150) in the other of said first and second members.

Claim 6

Dependent Claim 48 words

A seat backrest according to any preceding claim, characterised in that at least one layer of low friction material (172,174) is positioned between the forward surface of said lumbar pad (122) and the portion of said cushion member (170) which is adapted to be engaged by said pad.

Claim 7

Dependent Claim 52 words

A seat backrest according to claim 5, characterised in that a layer of thin but relatively rigid low friction plastics material (172) is attached to the back surface of said cushion member and a layer of low friction woven material (174) is adhered to the forward surface of said lumbar pad (122).

Claim 8

Dependent Claim 78 words

A seat backrest according to any of claims 2 to 6, characterised in that said second member has a threaded nut means (154) thereon which is engaged by a threaded adjustment screw (156) mounted on said back portion, said second member (152) having longitudinally extending end portions (152', 152") which cooperate with apertured brackets (158) affixed to opposite sides of said back portion to permit said second member (152) to move longitudinally while restraining it against rotary movement.

Claim 9

Dependent Claim 30 words

A seat backrest according to any preceding claim characterised in that said cushion member (52, 170) includes a recessed area-in its rear surface for receiving said lumbar pad (24, 122).

Claim 10

Dependent Claim 46 words

A seat backrest according to claim 1 characterised in that a generally horizontal support member (38) is affixed to said rigid back portion (10), said support member (38) serving to increase the rigidity of the back member and having said spaced bearing means (38') integral therewith.

Claim 11

Dependent Claim 40 words

A seat backrest according to claim 9 characterised in that said support member (38) is a metal channel having a vertical rear web portion (38."') attached to said back portion (16) and upper and lower flange portions (38") extending forwardly.

Claim 12

Dependent Claim 78 words

A seat backrest according to claim 10 characterised in that said spaced bearing means (38') support said adjusting screw (36) for rotation in the space between said upper and lower flange portions (38"), said adjusting nuts (32) and their trunnion portions (32', 32") having a shape generally complementary to that of said metal channel so as to guide said nuts (32) for axial movement while preventing said adjusting nuts (32) from rotating when said screw (36) is rotated.

Claim 13

Dependent Claim 28 words

A seat backrest according to any preceding claim characterised in that said adjusting screw (36, 126) and said adjusting nuts (32, 140, 140') each have double lead threads.

Claim 14

Dependent Claim 48 words

A seat backrest according to any of claims 9 to 12, characterised in that movement limitation means (42, 43) are mounted relative to said adjusting screw (36) so as to limit the axial extent of movement of said adjusting nuts (32) in both of their directions of movement.

Claim 15

Dependent Claim 46 words

A seat backrest according to any of claims 9 to 13, characterised in that said link members (30) are generally channel shaped and include apertures (45, 46) in each of their flanges at one end which engage said trunnions (32', 32") on said adjusting nuts (32).

Claim 16

Dependent Claim 74 words

A seat backrest according to claim 14, characterised in that said link members (30) include apertures at their other end (30', 30") which are complementary to tabs (26') formed on said lumbar pad (24) and engaged therewith sufficiently loosely so as to permit some pivotal movement of said lumbar pad (24) about a horizontal axis in response to pressure applied to said cushion member (52) above or below said horizontal axis by an occupant.

Claim 17

Dependent Claim 42 words

A seat backrest according to any of claims 1 or 9 to 15, characterised in that said link members (30) are generally parallel to the screw (36) in the retracted position and generally perpendicular to the screw (36) in the extended position.

Seat backrest having an adjustable lumbar support

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