Lordosis support

Abstract

A lordosis support for a seat back rest, includes a support plate, tension members for holding the support plate between two frame legs of the seat back rest, the support plate having on each side at least one point of attack for a respective tension member, and an adjusting device for adjusting a tension force of the tension members by changing the distance between the two points of attack, wherein the distance between the two points of attack is adjustable and the adjusting device is configured to change this distance, wherein the support plate is a one-piece support plate, and the two points of attack are linearly moveably arranged at the one-piece support plate for translational movement.

Claims

1. A lordosis support for a seat back rest, comprising: a support plate, tension members for holding the support plate between two frame legs of the seat back rest, the support plate having on each side a point of attack for a respective said tension member, and an adjusting device for adjusting a tension force of the tension members by changing the distance between the two points of attack, wherein the distance between the two points of attack is adjustable and the adjusting device is configured to change this distance, wherein the support plate is a one-piece support plate, and the two points of attack are linearly moveably arranged at the one-piece support plate for translational movement, wherein the tension members are formed by sections of a cable that extends continuously from one frame leg to the other frame leg, and is slidably guided over the points of attack at which is deflected such that it assumes a trapezoid-shaped configuration when seen in a direction in parallel with the frame legs.

2. The lordosis support according to claim 1, further comprising a counter bearing attached directly to each point of attack.

3. The lordosis support according to claim 2, wherein the adjusting device includes a Bowden cable having an outer cable attached to one said counter bearing and an inner wire attached to the other said counter bearing, and an adjusting device attached to an opposite end of the Bowden cable for changing the distance between the two points of attack.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiment examples will more described in conjunction with drawings, wherein:

(2) FIG. 1 is a schematic view of a lordosis support between two frame legs of a seat back rest;

(3) FIG. 2 is a section along the line II-II in FIG. 1;

(4) FIG. 3 is a view corresponding to FIG. 1, but for a different adjustment position of the lordosis support;

(5) FIG. 4 is a section along the line IV-IV in FIG. 3;

(6) FIGS. 5 and 6 are sketches of a lordosis support according to another embodiment in two different adjustment positions; and

(7) FIG. 6a is a sketch of the lordosis support of FIG. 5, showing the adjustment device therefor.

DETAILED DESCRIPTION

(8) The lordosis support shown in FIG. 1 has a support plate 10 that is held between two parallel frame legs 14 of seat back rest by means of two tension members 12 in the form of flexible bands. The support plate 10 has been formed for example by plastic injection molding and is composed of two half-plates 16 which have identical shapes and are displaceably held in engagement with one another in positions rotated by 180 relative to one another. To that end, each half-plate has a projecting tongue 18 that is displaceably guided in a complementary duct 20 of the respective other half-plate.

(9) At the edges facing away from one another, each of the half-plates 16 has a respective point of attack 22 for the associated tension member 12. This point of attack 22 is formed for example by a slot-like structure in which a corresponding bulge of the tension member 12 is anchored in a form-fitting manner.

(10) On one side of the seat back rest, at the right frame leg 14 in this example, a known adjusting device 24 for adjusting the lordosis support has been arranged. The adjusting device has a Bowden cable 26 the outer cable of which is supported at a counter bearing 28 of the one half-plate 16 whereas the inner wire is anchored at a counter bearing 30 of the other half-plate.

(11) When the back of the user exerts a force onto the support plate 10 via the cushioning of the seat back which has not been shown here, the flexibility of the tension members 12 permits the support plate to yield to some extent, as has been shown in FIG. 2. The principal plane of the support plate 10 is therefore slightly offset (downwardly in FIG. 2) relative to the plane that is defined by the frame legs 14. The tension members 12 are tensioned and therefore have the tendency to draw the two half-plates 16 of the support plate apart. This separating movement is however inhibited by the Bowden cable 26, so that the support plate 10 may not yield further and, consequently, exerts a support action onto the back of the user.

(12) Since, in this example, the support plate 10 is subject only to tensional forces that have the tendency to draw the two half-plates apart, all that is required of the adjusting device 24 and the Bowden cable 26 is to be configured such that these tension forces can be absorbed. Consequently, the inner wire of the Bowden cable 26 needs not translate any thrust forces in this embodiment.

(13) When the user wishes to adjust the lordosis support so as to be harder, she draws the two half-plates 16 closer together by means of the adjusting device 24 and the Bowden cable 26, as has been shown in FIGS. 3 and 4. This reduces the distance between the two points of attack 22, and the tension members 12 are subject to an additional tension force causing the support plate to be drawn closer to the plane defined by the frame legs 14.

(14) Just for the purpose of comparison, FIGS. 2 and 4 also show a lower frame leg 32 of the seat back, which lower frame leg is shown as a reference for the position of the support plate 10 and thus facilitates to recognize the different positions of the support plate in FIGS. 2 and 4.

(15) It is an advantage of the arrangement described herein that the relative movement between the two half-plates 16 of the support plate occurs in a horizontal direction, i.e. in the direction in which also the Bowden cable 26 enters into the interior of the seat back. The force of the Bowden cable may therefore be transmitted directly to the half-plates 16 without any need for a deflection or change of the direction of action. The tension members 12 may simply be formed by short bands or, as the case may be, also by injection-molded plastic film hinges each of which has one end firmly connected to one half-plate 16 and the other end firmly anchored at the frame leg 14.

(16) The construction is self-centering, i.e. the support plate is always in the central position between the two frame legs 14, regardless of the respective adjustment position of the Bowden cable 26. Moreover, the invention facilitates to arrange a support plate in the respectively desired height between the frame legs 14, and it is possible to provide means for height adjustment, if desired.

(17) The two half-plates 16 of the support plate having practically identical shapes can efficiently be produced in the same injection molding die.

(18) Commonly, the support plate 16 has the shape of a slightly curved basket that is concave on the side facing the user. In the embodiment that has been shown here, the width of the support plate is also varying in accordance with the distance between the points of attack 22. When the lordosis support is adjusted to be soft, as in FIG. 2, the support plate has a larger width. Nevertheless, the user is well-supported against lateral forces, because the entire structure formed by the support plate 10 and the tension members 12 forms a deep recess for the back of the user in this condition. When, in contrast, the lordosis support is adjusted to be hard, as in FIG. 4, the two half-plates move closer together, and the relief of the support plate becomes narrow, so that good lateral support for the spine of the user can still be obtained, although the lordosis support does not form such a deep recess in this condition.

(19) Instead of composing the support plate 10 of two parts, it is also possible in another embodiment just to provide adjustable points of attack at a one-piece support plate. An example of this variant has been shown in FIGS. 5 and 6. There, the tension members 12 are formed by a continuous cable that has a constant length and extends from one frame leg 14 to the other. As the case may be, a plurality of such cables may be provided in different heights. A one-piece support plate 10 is supported at the cable with its left and right lateral edges and thus causes a trapezoid-shaped deflection of the cable. Points of attack 22 for the tension members 12 are in this case formed by ledges that extend in vertical direction, (normal to the plane of the drawing in FIG. 5) and form on the back side of the support plate, i.e. on the side facing the cable, a slightly elevated bulge at which the cable is deflected. The two points of attack 22 are displaceably guided in the support plate 10, so that the distance between them can be changed by means of an adjusting device which has not been shown here, the effect of the adjustment been visible by comparing FIGS. 5 and 6.

(20) When the distance between the points of attack 22 is reduced, this causes the length of the tension members 12 to be increased because the total length of the cable is constant. On the left side in FIG. 6, two stretches x and y have been drawn which form a right-angled triangle with the tension member 12. When the length of this tension member is designated as z, it follows from the theorem of Pythagoras:
y.sup.2=z.sup.2x.sup.2.

(21) When, now, the points of attack 22 are displaced inwardly by a distance d, the quantity x has to be replaced by x+d. The central part of the cable between the points of attack 22 is shortened by 2d, and this is compensated by the length of each tension member being increased by d. Consequently, z has to be replaced by z+d, and the result is:
y.sup.2=(z+d).sup.2(x+d).sup.2=z.sup.2x.sup.2+2d(zx).

(22) As z is larger than x, this means that increases in proportion to d. Consequently, y increases in proportion to the square root of d. As y designates the distance between the plane of the frame legs 14 and the plane of the support plate 10, this means that the support plate 10 moves further away from the plane of the frame legs, i.e. the lordosis support becomes more compliant.

(23) FIG. 6a shows the arrangement of FIGS. 5 and 6, which uses the Bowden cable arrangement of FIGS. 1-4.

(24) As shown, counter bearings 28 and 30 are attached directly to the points of attack 22. Counter bearings 28 and 30 have been shown in a somewhat elevated position only for the purpose of clarity of the drawing.

(25) The equivalent of the tension members 12 of FIG. 4 are tension members 12 in FIG. 6a. The only difference is that tension members 12 do not hold the support plate 10 which is now held by tension member 34. This, however does not affect the adjusting mechanism.

(26) The tension members 12 form part of the adjusting mechanism in that they draw apart the points of attack 22, respectively, so that the Bowden cable 26 only functions to draw them together. The outer cable of the Bowden cable 26 is supported at counter bearing 28 whereas the inner wire is anchored at counter bearing 30. An adjusting device 24 which is the same as adjusting device 24 in FIGS. 1-4, is connected with the opposite end of Bowden cable 26, for adjusting the lordosis support, and operates in the same manner as adjusting device 24 of FIGS. 1-4.