Abstract:
An adjustable vehicle seat comprises a structurally fixed part, at least one adjustable part mounted for moving relative to the structurally fixed part, and an inflatable cushion positioned between the adjustable part and the structurally fixed part. The inflatable cushion is operative for pneumatically adjusting the position of the adjustable part relative to the structurally fixed part. The pneumatic adjustment of parts of the vehicle seat has the advantage that the compressed air supply which is already available can be shared, making additional electric motors for adjustment purposes unnecessary.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a vehicle seat, in particular for a truck, having at least one structurally fixed part and at least one adjustable part which is movable relative to the structurally fixed part. 
     A known vehicle seat of this type has a seat frame which can be adjusted vertically by means of a scissors-type substructure and an electric motor mounted thereon. 
     It is an object of the present invention to provide an improved vehicle seat of the type mentioned at the beginning. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, an adjustable vehicle seat comprises a structurally fixed part, at least one adjustable part mounted for moving relative to the structurally fixed part, and an inflatable cushion positioned between the adjustable part and the structurally fixed part. The inflatable cushion is operative for pneumatically adjusting the position of the adjustable part relative to the structurally fixed part. 
     In the case of trucks, including coaches, the pneumatic adjustment of parts of the vehicle seat has the advantage that the compressed air supply which is already available can be shared, making additional electric motors for adjustment purposes unnecessary. This simplifies and reduces the cost of the production of the vehicle seat. The inflatable cushion between the adjustable part and the structurally fixed part means that the pneumatic adjustment can take place with few components and in a simple manner. A vehicle seat of this type can be produced with little outlay on material and in terms of time and is thereby cost effective. 
     In one preferred embodiment, adjustable side pieces are provided which are coupled to a backrest frame of the vehicle seat and can be adjusted in their pivoting angle with respect to the backrest frame. In order to arrange the inflatable cushion in such a manner that it does not interfere with the seat user, the side pieces preferably have angular elements which are, for example, formed integrally with the side pieces or are welded onto the latter, and which reach as far as the rear side of the structurally fixed part. In accordance with one aspect of this embodiment, the structurally fixed part is a lordosis support that is connected to the backrest frame. At least one tension spring is preferably provided between the angular elements on the rear side of the structurally fixed part, which tension spring attempts to position the angular elements against the rear side of the structurally fixed part. A respective inflatable cushion is preferably provided between each angular element and the rear side of the structurally fixed part, which cushion attempts to push the relevant angular element away from the rear side of the structurally fixed part counter to the force of the tension spring. Two cushions have the advantage over one cushion in that no unintentional changing of the adjustment takes place due to a side piece being stressed on one side when cornering. In the case of a single cushion, the cushion would assume an asymmetrical form due to the air flowing from one half into the other. In order to protect the cushions, and as the stop for the angular elements, a covering is preferably provided on that side of the angular elements which faces away rearward from the rear side of the structurally fixed part. 
     In another preferred embodiment, the vehicle seat has a structurally fixed seat-shell rear part and a seat-shell front part which can be adjusted pneumatically in its inclination. A seat cushion which is fastened or rests on the seat-shell front part and on the seat-shell rear part defines the seat surface. For a thigh support, it is sufficient if only the seat-shell front part is adjustable. Greater seat comfort can be achieved by adjusting the seat-surface length. More specifically, the seat-shell front part can be displaced relative to the seat-shell rear part, for example by the seat-shell front part being guided on a carrier plate coupled to a structurally fixed seat frame. As a result, and for example, a multi-adjustable vehicle seat is provided with few components. For reliable guiding during the seat-surface length adjustment, slideways are provided on the seat-shell front part and/or on the carrier plate. The seat-shell front part is preferably locked by means of a locking bar which is mounted movably on the carrier plate, is movable relative to the seat-shell front part and, for locking purposes, interacts with a toothed segment of the seat-shell front part. This makes reliable locking and easy unlocking possible. For better performance during a crash, it is advantageous if the locking bar is movable transversely to the seat longitudinal direction. In order to enable adjustment in a gap-free manner in the various seat-surface lengths, the seat cushion reaches, for example, a small distance below the backrest. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention is explained in more detail with reference to an exemplary embodiment illustrated in the drawings, in which: 
     FIG. 1 shows a schematic side view of a vehicle seat according to one exemplary embodiment of the invention, 
     FIG. 2 shows a perspective view of a seat frame, 
     FIG. 3 shows a plan view of a carrier plate in the direction of the arrow III in FIG. 4, 
     FIG. 4 shows a front view of the seat frame and carrier plate in the direction of the arrow IV in FIGS. 2 and 3, 
     FIG. 5 shows a perspective view of a seat-shell front part, 
     FIG. 6 shows a front view of a backrest structure, 
     FIG. 7 shows a rear view of the backrest structure, and 
     FIG. 8 shows a section through the left half of the backrest structure along the line VIII—VIII in FIGS.  6  and  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with one exemplary embodiment, a vehicle seat  1  is fitted in a truck as a driver&#39;s seat. The following directional indications refer to the orientation specified by the normal direction of travel. The vehicle seat  1  is provided with a steel seat frame  3  which has: two parallel side parts  5 , which are arranged in the longitudinal direction, have an essentially U-shaped profile, and are designed such that they are upwardly open; a planar connecting plate  7 , which is arranged transversely to the side parts and connects the two side parts  5  in the front region on the upper side; an at least partially planar seat-shell rear part  9 , which is arranged transversely to the two side parts  5  and connects the two side parts  5  in the rear region on the upper side; and two fastening plates  11  which are mounted laterally on the seat-shell rear part  9 . The side parts  5  are connected on their lower side to the vehicle structure. The fastening plates  11  are provided with holes and welded-on nuts or with threaded holes in order to fasten a backrest structure to the seat frame  3 . 
     On each limb of their U-shaped profile, the side parts  5  each have a hole  5 ′ which is arranged, in the longitudinal direction, approximately in the center of the corresponding side part  5 . The four holes  5 ′ in total are all aligned transversely to the longitudinal direction and are flush with one another. A respective bearing bush  12  is inserted between the two holes  5 ′ of each side part  5 . A respective bearing bolt  13  is pushed through each bearing bush  12  and the relevant two holes  5 ′ and is secured at its ends. The two bearing bushes  12  can be rotated relative to the two side parts  5  and the two bearing bolts  13 . 
     An essentially planar carrier plate  16  has, on its lower side, two parallel U-profiles  18  running in the longitudinal direction. At its rear end, in the region of the rear edge of the carrier plate  16 , one of the bearing bushes  12  is in each case inserted through each U-profile  18  and fastened. The carrier plate  16  can thereby be pivoted relative to the seat frame  3 , the U-profile  18  at least partly fitting into the front half of the corresponding U-shaped profile of the side parts  5 . 
     An inflatable cushion  21  is provided between the connecting plate  7  and the carrier plate  16 , which cushion is connected via a connection to the compressed-air supply of the truck. By admission of compressed air, the cushion  21  can raise the carrier plate  16  and initiate a pivoting movement of the carrier plate  16 , as a result of which the front edge of the carrier plate  16  is raised. Releasing compressed air out of the cushion  21  enables the carrier plate  16  to be lowered again. The releasing of the compressed air is assisted by the body weight of the seat user. 
     On its upper side, the carrier plate  16  has a respective slideway  24  above each U-profile  18 . An essentially planar seat-shell front part  26 , which is made of sheet metal and has a rounded front edge and raised border to the side and toward the front in order to attach the cover, has two parallel sliding fixtures  28  which are punched out of the material of the seat-shell front part  26 . Each sliding fixture  28  holds a slideway  24 . As a result, the seat-shell front part  26  can be displaced in the longitudinal direction relative to the carrier plate  16 . 
     In order to secure a selected longitudinal adjustment of the seat-shell front part  26 , the latter has, below an upwardly bent tooth covering  30 , a toothed segment  32  whose teeth face toward the inside of the vehicle seat  1 , i.e. toward the right seat side in the exemplary embodiment. The toothed segment  32  interacts with a movable locking bar  34 . The locking bar  34  has a flat, elongated basic shape in the manner of a strip, the end sections  34 ′ and  34 ″ being bent upward or downward at right angles with respect to the basic shape. 
     The locking bar  34  is arranged and mounted movably on the lower side of the carrier plate  16  transversely to the longitudinal direction of the vehicle seat  1  between the center and the left seat side. The carrier plate  16  has two side guides  36  and a retaining guide  38 , arranged between the side guides  36 , the guides in each case being produced by pressing out of material, or else may be formed as a separate plastic part. The side guides  36  and the retaining guide  38  hold the locking bar  34  and are aligned in such a manner that the locking bar  34  is easily movable with little play. The side guides  36  are responsible for guiding in the plane parallel to the carrier plate  16  while the retaining guide  38  bears the weight of the locking bar  34  and keeps the latter bearing against the carrier plate  16 , i.e. is responsible for guiding perpendicularly to the plane of the carrier plate  16 . 
     The upwardly bent end section  34 ′ of the locking bar  34  protrudes as far as the upper side of the carrier plate  16  through the side guide  36 , which is situated further inward, or through an adjacent aperture  40  of the carrier plate  16 , the aperture  40  being provided for installation of the locking bar  34 . This end section  34 ′ is provided with a latching opening or the like with which it can interact with one of the teeth of the toothed segment  32 . The downwardly bent end section  34 ″ of the locking bar  34  is arranged a sufficient distance on the left border of the carrier plate  16  that it comes to lie outside the side parts  5  irrespective of the pivoting position of the carrier plate  16 . 
     By admission of compressed air to this end section  34 ″, the locking bar  34  can be pressed away inward by a tooth of the toothed segment  32 , so that the seat-shell front part  26  is unlocked and can be displaced with respect to the carrier plate  16  and can be adjusted in length. The locking bar  34  is pushed back outward by spring force, thereby locking the toothed segment  32  and therefore securing the seat-shell front part  26  on the carrier plate  16 . 
     The front part of a seat cushion  42  is mounted on the seat-shell front part  26 . A panel (not illustrated in the drawing) made of plastic is mounted along the border of the carrier plate  16 . The rear part of the seat cushion  42  rests loosely on the seat-shell rear part  9 . A backrest, which is only outlined in FIG. 1, is arranged above the rear end section of the seat cushion  42 . The seat cushion  42  is sufficiently long that, even when the length of the seat surface is at its largest, there is still no vertical gap between the seat cushion  42  and backrest. The described pivoting of the carrier plate  16  by means of the cushion  21  enables the seat-surface inclination of the seat cushion  42 , in particular the thigh support, to be pneumatically adjusted. The described displacement of the seat-shell front part  26  and the pneumatic unlocking and locking by means of the locking bar  34  enable the seat-surface length of the seat cushion  42  to be adjusted. The wiring and valve system necessary for the pneumatic adjustment is not illustrated in the drawing. 
     FIGS. 6 and 7 show the backrest structure before the padding is attached. The backrest structure is defined by a backrest frame  51  and the parts described in the following. The bow-shaped backrest frame  51  is bent from a square profile and fastened at the ends of its limbs to fittings  53 , which are mounted in turn on the fastening plates  11 . A lordosis support  55 , which is designed approximately as a rectangular plate, is arranged in the lumbar region between the limbs of the backrest frame  51  and is attached to the backrest frame, i.e. is structurally fixed. 
     The backrest frame  51  is designed such that it is mirror-symmetrical on the left and right with regard to a vertical central plane, for which reason only the left side is described in more detail in the following. On each of the two limbs, the backrest frame has two holders  57  which protrude forward. Arranged between the two holders  57  is a side piece  60  which is mounted in the two holders  57  and can be pivoted about a rotational axis running parallel to the limb of the backrest frame  51 . 
     An angular element  62  is mounted on the inside of the side piece  60 , for example is welded on, but may also be formed integrally with the side piece  60 . The angular element  62  is bent away from the side piece  60  about an edge running parallel to the rotational axis of the side piece, grips through a recess  55 ′ of the lordosis support  55  and, on the rear side of the lordosis support  55 , is bent away once more about an edge running parallel to the rotational axis of the side piece  60 . In total, the angular element  62  approximately comprises an angle of 60°. On the inwardly situated end, the angular element  62  has a hook-in opening into which one end of a tension spring  64  is fitted. The other end of the tension spring  64  is fitted to the right angular element  62 . The tension spring  64  causes the side pieces  60  to open. 
     A covering  67  is arranged behind the lordosis support  55  essentially parallel thereto. In the region of the left and of the right border, the covering  67  is angled obliquely forward and is fastened, for example welded on, to the backrest frame  51 . The covering  67  has a cross-shaped opening  69  in its center. The material which is bent forward upward and downward in order to form the vertical arms of the cross-shaped opening  69  forms webs  67 ′ with which the covering  67  is fastened to the lordosis support  55 . The horizontal arms of the cross-shaped opening  69  leave the hook-in openings in the angular element  62  free for the tension spring  64 . 
     A respective further cushion  71 , which is enclosed by a flexible casing and can be inflated up to a certain size, is arranged as an air chamber between each angular element  62  and the rear side of the lordosis support  55 . FIG. 7 illustrates the two cushions  71  with dashed lines, because the two cushions are hidden from view in FIG.  7 . The two cushions  71  are connected to the compressed-air supply via a double valve (not illustrated). If the double valve simultaneously admits compressed air to the cushions  71 , they increase in size, so that the angular elements  62  are pressed away from the lordosis support  55  counter to the force of the tension springs  64 . As a result, the side pieces  60  pivot inward. The covering  67  limits the movement of the two angular elements  62 . There is no connection between the two cushions  71 , so that no air can flow from one cushion  71  into the other cushion  71 . 
     If the compressed air is released out of the cushions  71 , the cushions  71  are compressed by the force of the tension spring  64  and therefore bled of air, so that the angular elements  62  again move toward the lordosis support  55  and the side pieces  60  pivot outward as a result. The side pieces  60  can therefore be pneumatically adjusted with regard to their pivoting angle with respect to the backrest. 
     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.