Abstract:
A vehicle seat has a rear cushion part and a front cushion part which is movable relative to the rear cushion part for adjusting the depth of the vehicle seat. The front cushion part and the rear cushion part are designed and constructed separate from each other and covered with a common cover.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device for adjusting the depth of a vehicle seat, in particular an automobile seat. 
     DE 41 04 440 C2 discloses a known seat depth adjusting device. In this known device, a flexible cushion part that is made as a one-piece cushion is provided with a continuous upholstered surface. The front portion of the flexible cushion rests upon a support member that is slideable for adjusting the seat depth. Depending on the desired seat depth, the front portion of the cushion is bent more or less over the front edge of the support member, with a spring compensating for the travel and providing the necessary tension. This seat depth adjusting device prevents a so-called crumbling fold. A crumbing fold occurs when separate cushion parts are present without a continuous upholstered surface. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is an improved seat depth adjusting device. In accordance with this aspect, a seat part having an adjustable depth includes separate front and rear cushion parts. The front cushion part is mounted for being movable relative to the rear cushion part for adjusting the depth of the seat. The seat part further includes a cover extending over both the rear cushion part and the front cushion part. The cover is mounted so that it serves as a continuous, exterior upholstered surface extending over both the rear cushion part and the front cushion part. In accordance with one aspect of the present invention, a vehicle seat is provided. The vehicle seat includes the above-described seat part and a seat back positioned at a rear edge of the seat part. 
     Because the front cushion part and the rear cushion part are made separate from each other, it is relatively easy to move the front cushion part for adjusting the seat depth. In accordance with one aspect of the present invention, the front cushion part contacts the rear cushion part and deflects (e.g., bends) as it is moved relative to the rear cushion part. As a result of the deflection, the front cushion part undergoes no squeezing in the region of the front edge of the seat part. Advantageously, there is significant latitude in the selection of the thickness of the cushion parts, and manufacture can be relatively simple and cost favorable. As an additional advantage, a crumbling fold is prevented by the common cover. 
     In a preferred embodiment, the front cushion part is rotatable relative to the rear cushion part. This has the advantage of a simple manufacture and assembly. For example, the front cushion part can be rotated via a drive unit with a longitudinally displaceable push bar, which engages the front cushion part preferably off-center, i.e., approximately in the fashion of a connecting rod. In combination with a noncircular front cushion part, this causes a rotational movement, during which the front cushion part is moved forward and back over different distances. Due to the lever arm conditions, the off-center engagement of the drive with respect to the axis of rotation has the advantage that the drive force is smaller than, for example, in the case of a drive via a shaft in alignment with the axis of rotation. 
     In a further preferred embodiment, the front cushion part is arranged on a profiled base support, which has for example, a substantially triangular cross section, namely a cross section with rounded corners and bent sides. This base support preferably has a supporting mechanism mounted to one of the corners, and the drive unit, with its off-center engagement, is joined to the base support in the region of another one of the corners. In accordance with one example, a corner or a side of the triangle is oriented upward toward the cover at the smallest or greatest seat depth, and the triangle is rotated between the smallest and greatest seat depths. The front cushion part has on its upper side a different length as a function of the position of the triangle. In all positions, the two cushion parts are so close together that the upper seat surface that is provided by the upholstery material is supported by the cushion parts over substantially its entire length. 
     In accordance with one aspect of the present invention, material with little friction (for example, nonwoven/leather) is paired between the cover and the front cushion part for purposes of keeping frictional forces low during the movement of the front cushion part relative to the cover, namely for purposes of not having to overdimension the force that is to be applied by the drive unit. So that the cover remains taut and does not pucker, and for purposes of compensating for the amount of the cover that is needed when the seat depth is enlarged, it is preferred to provide an elastic adjusting element, for example, a rubber band or a spring. In the case of greater adjusted depths, it is preferred to cause the elastic adjusting element to follow, for example, the mounting point of the adjusting element by a corresponding kinematic motion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention is described in more detail with reference to an embodiment illustrated in the drawings, in which: 
     FIG. 1 is a partially sectioned side view of the embodiment in the case of the smallest adjustable seat depth; and 
     FIG. 2 is an illustration similar to FIG. 1 in the case of the greatest adjustable seat depth. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention may be embodied in many different forms and should not be construed as limited to the embodiment set forth below; rather, this embodiment is provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout. 
     A seat  1  of an automobile is provided with a seat part  3  and a seat back  4  arranged at the rear edge of seat part  3 . In the drawing, the seat back  4  is indicated by dashed lines. The seat part  3  includes a seat bucket  5 , which mounts a seat cushion  7  serving as a padding. The seat depth, namely the spacing between the front edge of the seat part  3  and the seat back  4 , is adjustable by means of a seat depth adjusting device, which is described in greater detail in the following. 
     The front edge of seat bucket  5  mounts a forward extending holder  9  on the left and the right side of the automobile seat  1 . A profiled base support  10  has a cross section that remains substantially unchanged over the length of base support  10  and has the shape of a triangle with two rounded corners. The base support  10  can be made of plastic, and it preferably encloses only somewhat more than two sides of the triangle. The base support  10  extends transversely to the automobile seat  1 . The base support  10  includes at its two ends, in the region of a corner of the triangle, respectively one pair of parallel side plates  12  and a bearing pin  14  therebetween. The bearing pins  14  are in alignment with each other and oriented transversely to the automobile seat  1 . In addition, each bearing pin  14  extends through one of the holders  9  for rotatably supporting the base support  10 . 
     The base support  10  mounts a front cushion  16  of foam, which has a more rounded cross section than the base support  10 . On the base support  10  in the center between the bearing pins  14 , but off-center in the region of a further corner of the triangle, a further side plate  18  is provided. A drive unit  22  is mounted to the side plate  18  via a pin  20 . The drive unit  22  is obliquely oriented and mounted to the seat bucket  5 . The drive unit  22  includes a linearly displaceable push bar  24  that is moved, for example, by means of an electric motor or by hand, via a gear connection, or via a hydraulic or pneumatic cylinder. 
     The base support  10  with cushion  16  is arranged such that the cushion  16  lies with one corner or with one side of the triangle against the seat cushion  7 . The base support  10  with cushion  16  forms the front edge of the seat part  3 . A cover  27  forming the upholstered surface of the seat part  3  extends over the upper side of seat cushion  7  and cushion  16  and over the front edge downward to the underside of base support  10 , where a rubber band  29  is attached as an elastic adjusting element to the cover  27 . The rubber band  29  is attached to a transverse bar  31  that extends crosswise to the vehicle seat  1  and is secured to holders  9 . In accordance with one embodiment, the transverse bar  31  is designed and constructed such that it is displaceable by means of drive unit  22  along holders  9 . At least the underside of cover  27  and the upper side of cushion  16  are made of paired materials with little friction, for example, a nonwoven and leather. More specifically and in one example, the underside of cover  27  is made of leather and the upper side of cushion  16  is made of a nonwoven material. 
     At the smallest seat depth, the base support  10  with cushion  16  is adjusted such that one corner of the triangle points upward. To change the seat depth, the drive unit  22  moves its push bar  24  linearly in its longitudinal direction, thereby causing the front portion of drive unit  22  to displace forward. This displacement acts upon pin  20  and is superposed by a slight pivotal movement. The base support  10  is moved via pin  20 , which is arranged in off-center relationship to bearing pins  14 . In so doing, it performs a rotational movement about bearing pins  14 . As a result, the side of the triangle behind the previously upward directed corner slowly slides upward. During the movement, a shearing stress is exerted on cover  27  via friction, and a tensile stress via the enlarging surface. To compensate for the latter, the elastic band  29  stretches. If need be, transverse bar  31  is moved in addition, as mentioned above. At the greatest seat depth, the base support  10  with cushion  16  is adjusted such that the aforesaid corner of the triangle points forward, and that the side following it points almost exclusively upward. In the opposite direction of adjustment, the rubber band  29  provides the necessary tension in the cover  27 . 
     Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.