Abstract:
A height-adjustable support for semitrailers wherein the foot plate is suspended on tension springs which are arranged in two parallel planes situated in each case between the track roller and the wall of the inner support tube, and is fastened to the foot plate by one eyelet in each case in the inner support tube and the other eyelet in the vicinity of the transverse axis, and in that the foot plate corresponds with the inner support tube by a retaining device which is not permanently in engagement.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a height-adjustable support for semitrailers. 
   Supports of this type, usually arranged in pairs, are arranged in the front region of the semitrailer. A respective supporting foot with a foot plate, on which at least one rolling element rolls, is situated at the lower end of the extendible inner support tubes. The supports are used whenever the semitrailer is parked separately from the articulated lorry. In the case of the semitrailers which are prevalent nowadays and have air-sprung axles, the axle region may drop during relatively long parked periods because of pressure losses in the air spring bellows. In this case, with the axle assembly generally braked during parking, the semitrailer is subjected to a longitudinal thrust forwards, which the foot plates of the support are incapable of following because of adherence to the ground. In this situation, the supports with rigid foot plates would be exposed to a high flexural and buckling stress which might result in them being damaged. In order to avoid this, the said rolling elements act in a thrust-compensating manner on the foot plates, i.e. the supports move forwards on the foot plate by the rolling elements rolling out of the central position. When the load on the supports is removed again during coupling-on of the semitrailer, spring elements ensure that the foot plates are returned again into the central position, i.e. symmetrically to the particular support axis. 
   A support of the generic type is known from EP 0 886 592 B1, with a rolling element being provided in the foot region, and wire cables and compression springs serving to fasten and reset the foot plate being proposed. A configuration of this type has a large number of parts. And, in this case, there is no further attachment means for the foot plate. 
   DE 40 03 414 C2, the supporting foot is of a what is referred to as a telescopic supporting device for semitrailers which a rolling segment as a cut-out opening of a hollow cylinder with a partially cylindrical convex surface as rolling surface, the convex surface having slots which extend in the circumferential direction and through which helical springs are passed, of which one is fastened at one end at the front of the foot plate and at the other end at the front of the support tube and the other is fastened at one end at the rear of the foot plate and at the other end at the rear of the support tube. In the direction of the end side, the helical springs are arranged such that they are exposed centrally with respect to the foot plate and are therefore permanently exposed without protection to the weather, which may result in corrosion damage and cause malfunctions. In this case the width of the rolling segment exceeds the width of the support and, due to the unfavourably great height of this supporting foot and the arrangement of its pivot axle, necessarily on the lowermost end region of the inner support tube, a semitrailer support provided in such a manner obtains a disadvantageous, large construction height. In addition, this supporting foot is pivotable only in one plane and cannot compensate in the transverse direction for any unevennesses of the ground, which may result in overstressing of the material in the case of uneven parking surfaces. In addition, after its suspension means are released, a foot of this type could be completely lost. 
   It is an object of the invention to provide a height-adjustable support of the type of construction referred to above, wherein the foot region of which, while retaining the smallest possible construction height with resetting elements arranged in a manner protected from the weather, has protected means of suspending the foot plate and causes less structural outlay. 
   SUMMARY OF THE INVENTION 
   The object is achieved in that the foot plate is suspended on tension springs which are arranged in two parallel planes situated in each case between the track roller and the wall of the inner support tube, and is fastened to the foot plate by one eyelet in each case in the inner support tube and the other eyelet in the vicinity of the transverse axis, and in that the foot plate corresponds with the inner support tube by means of a retaining device which is not permanently in engagement. 
   This solution has the advantage that the tension springs in the basic position of the support, i.e. both during transportation and when parked, in a resting supporting function, are situated entirely within the inner support tube in a manner protected against dirt and the weather and are only partially exposed only during a thrust compensation of the support. In an advantageous manner, the retaining device between the foot plate and the inner support tube is designed in such a manner that it is generally not in engagement. The foot plate is therefore pivotable to a sufficient extent both about its transverse axis and about its longitudinal axis. This pivotability on all sides with the possibility (which advantageously exists as a result) of adapting the foot plate to sloping ground is also ensured by the installation of a track roller, with a preferably cross-sectionally circular-arc-shaped concave track groove, into the inner support tube and a rolling track, of complementarily convex design with respect to the track groove of the track roller, on the foot plate. In contrast to a bar which conventionally penetrates a rolling segment and the side walls of the foot element and therefore, by means of tilting, prevents the foot element and the like from being adapted to the ground, in the case of the retaining device proposed there is absolutely no contact with other parts even when the foot plate is sufficiently pivoted transversely. The retaining device only comes into action if the tension springs should accidentally break at the same time, and it then brings about a secure interlocking of the foot plate with the inner support tube, so that the foot plate cannot be lost. 
   It is advantageous if centre-symmetrical stops are arranged on the inner support tube as lower extensions in pairs, the said stops having stop surfaces which are indented in each case in relation to the left and the right outer surfaces of the inner support tube and strike against stoppers situated on the foot plate upon maximum thrust compensation. Owing to the indented stop surfaces, the length of the foot plate can namely be kept short in a favourable manner. 
   If a fastening/locking attachment is provided which, sitting on the axle of the track roller in the inner support tube, serves both for fastening the springs and for axially fixing the axle, a preassembly of the subassembly of the foot region of the support is possible in a favourable manner. In addition, the outlay on a separate means of securing the axle against drifting out is also omitted. 
   Finally, it is advantageous to provide deflecting runners in the inner support tube, which deflecting runners gently deflect the tension springs, which are extended during the thrust compensation of the support. Also in an advantageous manner the deflection angles which arise in the process result in favourable spring force components during the resetting of the foot plate by the tension springs. It is particularly cost-effective to produce, i.e. to impress, the deflecting runners by means of a corresponding impressing of the shape in those wall portions of the inner support tube which are situated in the regions of the tension springs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention and its developments are described with reference to drawings of preferred exemplary embodiments. 
     In the drawings: 
       FIG. 1  shows a side view from the lower part of a support with the inner support tube retracted (transporting position), 
       FIG. 2  shows a front view, partially cut away, according to  FIG. 1 , but in the extended inner support tube (working position), 
       FIG. 3  shows a side view as  FIG. 1 , with the support being in the maximum compensation position with respect to the center of the foot plate, 
       FIG. 4  shows a front view, partially cut away, as  FIG. 2 , but in a different configuration, and 
       FIG. 5  shows a side view according to  FIG. 4 . 
   

   DETAILED DESCRIPTION 
   The supports  10  which are arranged in pairs on the front lower side and symmetrically to the longitudinal axis of the semitrailer (not shown here) each have a vertical outer support tube  11 , which is connected to the semitrailer frame, and an inner support tube  12 , which is arranged displaceably in said outer support tube, the cross sections of which tubes are generally square. The support tube  12  can be mechanically extended and retracted, i.e. can be brought from the transporting position into the working position by extension or from the working position into the transporting position by retraction. 
   Fastened in the lower end region of the inner support tube  12 , in the direction looking at  FIG. 1 , i.e. transversely to the direction of travel of the semitrailer, are two spaced-apart, aligned bearing housings  13  in which a cylindrical axle  14  is fixed. A track roller  15  is mounted rotatably on the axle  14  and, when the inner support tube  12  is extended, transmits the load pressure to a foot plate  16  resting on the ground and can roll along said foot plate. For this purpose, the track roller  15  has a cross-sectionally circular-arc-shaped, concave track groove  17  on the circumference, and the foot plate  16  has a rolling track  18  which is complementary to the track groove  17 , is of convex design and at the same time guides the track roller  15 . Apart from the raised rolling track  18  running centrally in the longitudinal direction, the upper side of the foot plate  16  has two reinforcing ribs  19  arranged in a mirror-inverted manner next to said rolling track. The reinforcing ribs  19  each comprise a vertical web region and a supporting edge  19   a  which is arranged thereon and points to the center of the foot plate  16 . At its lower end, the inner support tube  12  has a pair of center-symmetrical extensions  20  which each have stop surfaces  21  which are indented in relation to the left and the right outer surfaces of the inner support tube  12  and, upon maximum compensating distance of the support, strike against stoppers  22  sitting on the foot plate  16  and limit the compensating distance. In addition, two retaining pins  23 , which are situated opposite each other on the sides on which the extensions  20  are arranged and point outwards and under the particular supporting edge  19   a  of the reinforcing rib  19 , are situated on the inner support tube  12 . The supporting edges  19   a  of the reinforcing ribs  19  and retaining pins  23  form a retaining device  24  (described further on). The retaining pins  23  are generally spaced apart from the reinforcing ribs  19  and the foot plate  16 , so that the foot plate  16  is pivotable both about its longitudinal axis, for example at the angle α, and about its transverse axis, for example at the angle β, and can be adapted to the unevennesses of the ground. Tension springs  25  are situated in two parallel planes, in each case between one side of the track roller  15  and the opposite walls of the inner support tube  12 . The tension springs  25  are fastened in each case by the upper eyelet to a mount  26  in the inner support tube  12  and by means of their lower eyelet directly below the inner support tube  12  to a retaining/introducing tab  27  which sits on the foot plate  16 . When the inner support tube is retracted, the prestressed tension springs  25  first of all press the foot plate  16  in a favorable manner rigidly, i.e. not pivotably, in the transporting position against the lower edge of the outer support tube  12  and then, during the extension and retraction of the inner support tube  12 , pivotably against the track roller  15 . 
   If the support  10 , with its foot plate  16  standing on the ground, in addition to its supporting function is forced to migrate forwards—to the left in FIG.  1 —as the rear part of the semitrailer drops, the track roller  15  rolls along the foot plate  16 , in which case the tension springs  25  are tensioned more strongly. In the process, the tension spring  25  are gently deflected. This takes place, on the one hand, via deflecting runners  29 , which are arranged over cutouts  28  situated on the lower edge of the inner support tube  12 , and, on the other hand, on cylindrical regions of the bearing housings  13 . The deflecting runners  29  are impressed into the wall regions of the inner support tube. 
   During the subsequent coupling-on of the semitrailer, at the beginning of the retraction of the inner support tube  12  and the raising from the ground which takes place in the process, the foot plate  16  is pulled back by the tension springs  25  into its starting position according to  FIG. 1 . Towards the end of the retraction stroke of the inner support tube  12 , the retaining/introducing tabs  27 , which are provided with introducing bevels  27   a  and the outer distance between which is only slightly smaller in the installation planes of the tension springs  25  than the clear width of the outer support tube  11 , bring about a symmetrical fine alignment of the foot plate  16  with the outer support tube  11  when the transporting position is reached. If the tension springs  25  break at the same time, the retaining device  24  becomes effective for the sake of safety. The supporting edges  19   a  of the reinforcing ribs  19  and the retaining pins  23  on the inner support tube  12  then interlock, so that the foot plate  16  is not lost but rather remains hanging on the inner support tube  12 . 
     FIGS. 4 and 5  show a configuration of the support  10  with a fastening/locking attachment  30 . The fastening/locking attachment  30  engages partially around the upper region of the track roller  15 . It has, in addition to a central region, two vertical, downwardly protruding limbs  30   a  which have a symmetrical cut-out opening  30   b  there and sit in a form-fitting manner in grooves  14   a  of the axle  14 . During the preassembly of the subassembly of the foot region of the support  10 , the fastening/locking attachment  30  sits with its central region on the track roller  15 , in which case the tension springs  25 , after being hooked into the retaining/introducing tabs  27  of the foot plate  16 , can be hooked in a prestressed manner into receptacles  30   c  of the fastening/locking attachment  30 . The preassembled subassembly of the foot region is supported by the axle  14  which is introduced after the fastening/locking attachment  30  has been raised. In order to raise the fastening/securing attachment  30 , an auxiliary opening  12   a  is provided in the inner support tube  12  and two engagement slots  30   d  are provided in the fastening/locking attachment  30 , into which, for example, a screwdriver for use as a lever can be introduced. The limbs  30   a  of the fastening/locking attachment  30  latch with edge regions of their cut-out openings  30   b  into radial grooves  14   a  of the axle  14 , as a result of which there is a form-fitting securing of the axle  14 , which prevents it from drifting out of its mounting. The final securing of the axle  14 , for the purpose of removal, takes place in turn by levering raising of the fastening/locking attachment  30 , as described above, in which case the axle  14  can be pushed out.