Seat Backrest Having an Adjustable Lumbar Support

The present invention relates to vehicle seats and particularly to seat backrests of the type which include internal structures for selectively adjusting the seat cushion contour to provide varying degrees of lumbar support to a seat occupant.

The desirability for providing support for the lumbar region of the back of a seat occupant has long been recognized and various patents, including U.S. Pat. Nos. 3,807,794; 3,890,000; 3,948,558 and 3,973,797 disclose structures for permitting a fore and aft adjustment of an internal lumbar pad within a back cushion.

It is among the objects of the present invention to provide an adjustment lumbar support for a seat back which is simple to operate by a seated occupant and which provides positive positioning of the lumbar support.

The above and other objects are attained by the apparatus of the present invention wherein a lumbar pad member is supported for generally fore and aft movement by a pair of spring wire support arms which pivot about supports which are normally fixed relative to the seat back frame. The lumbar pad is resiliently biased to its extended position by a rigid toggle link which is pivoted at one end to the lumbar pad and the pair of support arms and at its other end to a vertically adjustable link which is movable in a guide channel which is integral with the seat back frame. The vertically adjustable link is actuated by a connecting link which is pivoted to a pivotally mounted handle member. The compactness of the structure permits its use in combination with existing seat back frames with only minor modifications.

FIG. 1 is a fragmentary perspective view of a seat back frame member incorporating the lumbar assembly in its intermediate adjustment position with the seat back cushion removed for clarity;

FIG. 2 is a partially broken away, partially sectioned, side view of a seat back with the lumbar support structure in its recessed, inoperative configuration; and

FIG. 3 is a partially broken away, partially sectioned, side view of a seat back with the lumbar support structure in its full forward, operative position.

Referring to FIG. 1, a formed metal seat back frame 10 can be seen as having a recessed pocket portion 12 defined by side portions 14 and a back portion 16. A pivot 18 is indicated as passing behind the seat back frame 10 and is used to pivotally mount the seat back by means of mounting angles (not shown) to brackets 20 formed on the seat base (not shown). A lumbar pad member 24 is preferably formed of metal and has struck out or welded on hinge portions 26 which capture the upper free ends 28 of a pair of formed spring wire arm members 30. A pair of stop members 32 are integrally attached to the lumbar pad 24 to retain the arm ends 28 in place. The lower ends 34 of the arms 30 are pivotally mounted in apertures in integral support bracket portions 36 and retained therein by integral retaining portions 38. The bracket portions 36, the retaining portions 38 and a pair of vertical guide channel portions 40 are all preferably formed by being bent out of base plate 44 which is welded to or otherwise fastened to the back portion 16. Fore and aft movement of the lumbar pad 24 along the pivot path of the end portions 28 of the pivoted arm members 30 is controlled by a plurality of levers and links connected by pivot pins. Starting at the lumbar pad 24, a wide, generally flat pivot link 48, which preferably has integrally formed strengthening ribs, has a horizontal hollow hinge portion at its outer end which receives the bent end portions 28 of the support arms 30. The inner or lower end of the link 48 also has horizontal hollow hinge portions which cooperate with complementary hinge portions on a vertically movable link 50 and are pivoted thereto by a hinge pin 52. The hinge in 52 extends axially outwardly from the hinge portions and is captured under the channel portions 40 which restrict the pin 52 and link 50 to movement in a vertical plane parallel to the plate 44. A pivot pin 54 extends horizontally from the vertical link 50 and is engaged by a connecting link 56 which is pivoted by a pivot pin 58 to the inner end of handle lever 60. The handle lever 60 is pivoted intermediate its ends to a pivot pin 62 carried by the base plate 44. Preferably, retaining rings are provided on each pin. The handle lever 60 passes through an opening 64 in one side wall portion 14. It has a handle grip 66 on its outer end and an integral projection portion 68 which is adapted to be moved into contact with a series of retaining notches 70 formed on a bracket 72 welded to the frame 10. A spring 74 carried by the lever 60 bears against the back portion 16 to bias the projection 68 into one of the notches 70 but permits the projection to be moved rearwardly of the notches and then up or down to vary the in and out position of the lumbar pad 24. When the handle 66 is raised to its highest position the lumbar pad 24 will be in its collapsed position shown in FIG. 2. When the handle 66 is in its lowest position, the lumbar pad 24 will be in its extreme forward position illustrated in FIG. 3 in which it forces the padding layer 76 outwardly towards the lumbar region of a seat occupant. By experimentation with different adjustment positions, a particular seat occupant can achieve the degree of lumbar support with which he feels most comfortable.

Although the arms 30 are retained by elements 38 and 32 throughout their operative range of movement, they are easily assembled initially by not immediately attaching pin 58 to link 56. This permits hinge pin 52 and link 48 to be raised above the channels 40 and the lumbar pad 24 to be moved far forwardly of its FIG. 3 position where the arms 30 will clear the elements 32 and 38.