Abstract:
A height-adjustable support ( 10 ) for semi-trailers or similar, comprising a locally fixed external support tube ( 13 ), an internal support tube ( 14 ), which is fixed to a nut ( 18 ) on a spindle ( 17 ), the spindle being driven by a change-over gear and a bevel gear assembly. The change-over gear has two gear wheel stages which can be alternately activated, a separate gear stage comprising bevel gear toothing being provided for the distribution of forces after each gear wheel stage.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a height-adjustable support for semitrailers or the like, comprising a locally fixed external support tube, an internal support tube, which is fixed to a nut on a spindle, the spindle being driven by a change-over gear and a bevel gear assembly. The change-over gear has two gear wheel stages which can be alternately activated, a separate gear stage comprising bevel gear toothing being provided for the distribution of forces after each gear wheel stage. 
     Supports of this type are disposed, generally in paired arrangement, as a supporting apparatus in the front region of the semitrailer. 
     An apparatus of this type is known from EP 0 675 0029. Here the speed-change gear mechanism is accommodated in a housing attached to the front of the support outer tube. The transmission input shaft and the transmission output shaft, on which the gearwheels are seated in a rotationally secure manner, are mounted respectively in the housing and in that wall of the support outer tube which lies opposite the housing. The transmission input shaft is in this case disposed below the bevel gear set, and alongside the spindle. The transmission output shaft is located above the ring gear, in whose upwardly directed toothing the bevel pinion seated in a rotationally secure manner on the transmission output shaft engages. The transmission input shaft can be rotated by means of a crank handle. The large gearwheel fitted on the transmission input shaft is provided in engagement with the smaller gearwheel, seated on the transmission output shaft, for a rapid height adjustment of the support; and the transmission generated by the pinion on the transmission input shaft with the large gearwheel on the gearwheel set of the transmission output shaft serves for the height adjustment of the support under load. Both in low-speed gear and in the faster height adjustment of this apparatus, the further power flow is effected via the bevel gear set to the spindle drive, and this apparatus is very bulky. 
     A pair of supports of the generic type is also known from EP 1 104 369 B1. The speed-change gear mechanism of this so-called apparatus for supporting the semitrailer of a truck tractor is disposed almost fully within the support, the transmission input shaft and the spindle disposed, for this purpose, outside the middle of the support being mounted in a common pillow block. The transmission input shaft and the transmission output shaft are mounted in a large cover, which is attached in protruding arrangement on the front wall of the support outer tube and which is also necessary to enlarge the installation space for the speed-change gear mechanism. The transmission input shaft arranged pointing to the spindle has a pinion, which engages in a large-diameter gearwheel of a gear set integral with the transmission output shaft and effects the transmission for a height adjustment under load. A further large-diameter gearwheel, which is mounted concentrically to the transmission input shaft, can be coupled and driven, following axial displacement of the transmission input shaft, by means of the pinion thereof. This latter large-diameter gearwheel hereupon engages in the pinion which belongs to the gear set of the transmission output shaft and via which the transmission for a faster adjustment of the support without load is realized. Disposed in a rotationally secure manner on the upper end of the spindle is a ring gear, in whose upward-pointing toothing the bevel pinion of the above-situated transmission output shaft engages. Here too, the bevel gear set is the second transmission stage both for the low-speed gear and for the faster adjusting process for the support. 
     In these known supports, it is particularly disadvantageous that behind the speed-change gear mechanism the power flow is effected always, i.e. both in the adjustment under load, the lifting process, and in the fast adjustment, the load-free height adjustment process, via one and the same bevel gear stage. Based on its large step-down ratio, the bevel gear stage is actually only fit for the lifting process. The result is that, in the previous transmission design for such supports, the speed increase attained via the step-up gear stage of the speed-change gear mechanism is very largely cancelled out by the step-down of the bevel gear set. And that the following spindle drive extends or retracts the support inner tube only at relatively moderate speed, even though this unsatisfactory process is referred to throughout the industry, for time-saving purposes, as the high-speed gear. 
     The object of the invention is to provide a height-adjustable support for semitrailers, which support has a particularly high high-speed gear in order to achieve a significant time gain, and in which all transmission parts are accommodated in the support outer tube without the need for a structural expenditure which enlarges the installation space. 
     SUMMARY OF THE INVENTION 
     This object is achieved according to the invention by the support according to the invention wherein it is proposed to provide a separate power transmission for high-speed gear operation from the speed-change gear mechanism into the spindle drive. For load operation, a first bevel gear set, as previously the norm, with step-down can be provided, which, together with the likewise speed-reducing speed-change gear mechanism stage before it and the spindle drive arranged after it, is ergonomically optimally designed with respect to the hand drive power. Regardless of this, the bevel gear set for the high-speed gear, on the other hand, is according to the invention particularly advantageously designed in terms of its transmission, if it has a substantially more direct transmission than the first-named bevel gear set. Thus in practice, for example, a transmission ratio of 1:1 already yields more than a doubling of the adjustment speed, with corresponding time savings compared with the traditional supports. 
     This design affords the possibility, in a superb manner, that the ring gears can be disposed above the transmission output shaft. 
     The transmission output shaft therefore no longer has to be led over the spindle and the ring gear, as previously, which, as a result of its consequently adverse height arrangement and predefined attachment height in the case of traditional supports, helps constructively to reduce the lift. 
     In a refinement, the invention provides a mounting support part, in which the transmission output shaft, as well as the spindle and a pinion unit installed therein, are jointly mounted. The transmission region of the support is hence made very compact. 
     According to the invention, the pinion unit to be disposed in the mounting support part preferably consists, in one-piece construction, of the pinion of the high-speed gear stage and the associated bevel pinion, as well as a small shaft. It is also conceivable, however, purely to connect the said pinions in a rotationally secure manner and to use for this purpose a small axle. 
     A gear unit of this kind can advantageously be inserted as a part from above into the mounting support and favorably requires no installation opening on the front side of the support. 
     According to another refinement according to the invention, the ring gear for the high-speed gear can be fastened on the spindle jointly with the ring gear for the low-speed gear, or the ring gear for the high-speed gear is fastened to the ring gear for the low-speed gear, which latter ring gear is fixed on the spindle. 
     The ring gear for the low-speed gear can also be provided with a second bevel gear toothing, corresponding to the ring gear for the high-speed gear, so that the latter ring gear is advantageously no longer required as a part. 
     And economically, the bevel toothings for the high-speed gear, because they are placed under less load, can be dimensioned smaller than those for the low-speed gear. 
     The four gearwheels of the speed-change gear mechanism are arranged such that the gearwheel and the pinion of the high-speed gear stage are disposed in front of, and the gearwheel with the pinion of the low-speed gear stage are disposed behind the spindle. 
     Because of this design according to the invention, the spindle can be centrally positioned and the advantageously short-length transmission output shaft can be disposed behind the spindle, pointing away therefrom. 
     If, according to the invention, the transmission input shaft is provided with preferably two radially protruding dogs as coupling means, these, after being appropriately engaged, can transport the large gearwheel, loosely mounted on the transmission input shaft, of the high-speed gear stage, or, for the low-speed gear, can transmit the torque to the pinion provided for this, and can also, in an intermediate setting, effect a freewheel. In this way, a cost-effective gearshift is realized. 
     The pinion of the low-speed gear stage of the speed-change gear mechanism is advantageously provided with a hollow shaft, in which the transmission input shaft can be mounted in an axially displaceable manner. Favorably, according to the invention, the necessary engagement regions for the dogs of the transmission input shaft can also be shaped on the hollow shaft of this pinion. 
     In an advantageous refinement of the invention, the transmission output shaft is preferably a part with square cross section and a cylindrical bearing journal and can be inserted in a positive-locking manner into the gearwheel/bevel gear stage, thereby greatly simplifying the assembly. 
     As another refinement of the invention, it is proposed to attach a motor in such a way to that support of a support pair which has no speed-change gear mechanism and is connected by a connecting shaft to the transmission output shaft of the support with speed-change gear mechanism, which latter support is drivable with a crank handle, that said motor can drive the hollow-shaft pinion. 
     Advantageously, a motorized drive of the support pair, for example for an automated hitching and unhitching operation with respect to truck tractors, is thereby enabled and manual operation can become the alternative for the special or emergency case. 
     In a bearing flange sleeve, three radial grooves are provided for the selective engagement of a ball spring element, seated in the transmission input shaft, for the purpose of locking the gearshift settings of the transmission input shaft. 
     In the engaged middle setting, in the aforesaid motorized operation, it is thus advantageously ensured that the speed-change gear mechanism of the manual drive remains in freewheel. 
     As another embodiment of the invention, for the separate high-speed gear power flow to the spindle drive, an intermediate drive unit having a toothed pinion as well as a bevel pinion is proposed, which shall be provided axially in front of a gearwheel and bevel pinion arrangement for the low-speed gear. Into the gearwheel and bevel pinion arrangement, on the support rear side, a transmission output journal can favorably be inserted positively from outside, by which the second support of a support pair can be driven. 
     The spindle with mounted ring gears, the toothings of which point upward, can here be stored in a bearing plate. 
     Advantageously, the transmission input shaft must be installed such that, in parallel arrangement to the intermediate drive unit, it extends only so far into the support outer tube as corresponds to the width of the large gearwheel of the high-speed gear and as its mounting depth in the hollow shaft pinion demands. 
     The gearwheel and bevel pinion arrangement for the low-speed gear can advantageously be shaped in one piece and provided with a bearing journal on which the intermediate drive unit can be mounted. 
     The bearing journal for the intermediate drive unit can also be provided as an extension on the transmission output shaft placed from behind through the gearwheel and bevel pinion arrangement, thereby facilitating the assembly. 
     It is advantageous to configure the intermediate drive unit in one piece such that it at one end receives a bearing bore, which is mounted on the bearing journal of the gearwheel/bevel pinion unit or on an extended transmission output journal, and at the other end is stored in the front region of the support. 
     The intermediate drive unit can also be shaped such that, instead of a bearing bore, it has a bearing journal, which is mounted in the gearwheel and bevel pinion arrangement for the low-speed gear or on the power-take-off journal, the bevel gear being fitted in a positive-locking manner, which produces a favorable means of assembly. 
     For a further embodiment of the support according to the invention, it is proposed to provide a gearwheel drive unit, which is disposed parallel to the intermediate drive unit and the gearwheel/bevel pinion unit and alternately transmits the power flow for the high-speed gear to the intermediate drive unit or, in low-speed gear, to the gearwheel/bevel pinion unit. 
     In preferably one-piece construction, the gearwheel drive unit, on one end region, can be configured with a large-diameter gearwheel for the high-speed gear operation and, at the other end, with a pinion for the low-speed gear. 
     The gearwheel drive unit can be connected in a rotationally secure and axially fixed manner to the transmission input shaft, which, in a manner appropriate thereto, must extend into the support outer tube by a still small extent than in the previously described embodiment. Apart from this connection and the thereby effected mounting of the gearwheel drive unit, it is advantageous to store the other side of the gearwheel drive unit displaceably on a bearing journal to be provided on the inner side of the rear wall of the support outer tube. 
     Through axial displacement of the transmission input shaft, the gearwheel drive unit is also correspondingly displaced and brought either into the high-speed gear or the low-speed gear, or in-between into neutral setting. In this embodiment, the unused gearwheel or pinion is respectively disengaged. 
     The support can advantageously also be provided with a bearing plate for the spindle, which bearing plate is cup-like and is preferably shaped with a square edge. At variance from the cup shape, individual edge regions may also be arranged taller. 
     If, moreover, the nut of the spindle drive is disposed in the support inner tube instead of over the support inner tube, the support inner tube can beneficially be extended upward to the point where its upper end face, in retracted setting, reaches up to directly against the bottom side of the edge of the proposed cup-like bearing plate. 
     If edge regions of the bearing plate are made taller, the side walls of the support inner tube, if stepped on the end face or provided with recesses, can also be correspondingly extended further upward. This gives rise to the possibility of building, according to the invention, supports with extremely low overall height and relatively large lift. In practice, this is advantageous with regard to ground clearance, especially in supports for large-capacity semitrailer units with low-lying frames. And in longer supports for higher vehicles, according to this embodiment there is a greater overlap of the support outer tubes with the support inner tubes, due to upwardly extended support inner tubes in the extended state. The increase in overlap favorably increases the transverse rigidity, and hence the operating reliability of the supports. 
     Finally, it proves favorable with regard to the gearwheel design if the transmission input shaft disposed above the intermediate drive unit of the high-speed gear is installed laterally offset from the intermediate drive unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is next explained with reference to the drawings, in which: 
         FIG. 1  shows a front view of the support according to the invention, 
         FIG. 2  shows a side view of the support shown in  FIG. 1 , 
         FIG. 3  shows a longitudinal section of the support shown in  FIG. 1  along the line A-A, with the speed-change gear mechanism in the high-speed gear setting, 
         FIG. 4  shows a second longitudinal section analogous to  FIG. 2 , wherein the speed-change gear mechanism can be seen in the low-speed gear setting, 
         FIG. 5  shows a third longitudinal section analogous to  FIG. 2 , wherein the speed-change gear mechanism can be seen in the high-speed gear setting, 
         FIG. 6  shows a fourth longitudinal section analogous to  FIG. 2 , wherein the speed-change gear mechanism can be seen in the high-speed gear setting, 
         FIG. 7  shows a fifth longitudinal section analogous to  FIG. 2 , wherein the speed-change gear mechanism can be seen in the high-speed gear setting, 
         FIG. 8  shows a sixth longitudinal section analogous to  FIG. 2 , wherein the speed-change gear mechanism can be seen in the high-speed gear setting, 
         FIG. 9  shows a seventh longitudinal section analogous to  FIG. 2 , wherein the speed-change gear mechanism can be seen in the high-speed gear setting, 
         FIG. 10  shows a front view of the upper support region. 
     
    
    
     DETAILED DESCRIPTION 
     The support  10  shown in  FIGS. 1 to 9  is fastened in paired arrangement to the chassis of a semitrailer in the front region thereof. The supports  10  of a pair are mutually connected by means of a connecting shaft  11  on the transmission output shafts  12  and in the transport setting are retracted, i.e. are in shortened state. And before the semitrailer is uncoupled from the tractor truck, they are extended. 
     The support  10  has a support outer tube  13 , and a support inner tube  14  mounted in a longitudinally displaceable manner therein. The support outer tube  13  and the support inner tube  14  preferably have square cross sections. The support  10  is fastened to the semitrailer frame by a screw-on plate  15  seated on the support outer tube  13 . Fastened to the lower end of the support inner tube  14  is a foot  16  for placement onto the ground. In addition, the support  10  has a spindle  17  with a nut  18 . 
     As shown by  FIGS. 1 to 4 , seated on the spindle shoulder is an axial bearing  19 , which is supported on a mounting support part  20  fastened in the support outer tube  13 . In the mounting support part  20 , the transmission output shaft  12 , the spindle  17  and a pinion unit  21  are jointly mounted. The pinion unit  21  consists, in one-piece construction, of a pinion  21   a , a bevel pinion  21   b  and a small shaft  21   c . For the installation and mounting of the pinion unit  21 , the mounting support part  20  has pockets  22 ,  23  and upwardly open bearing points  24 . Likewise, the mounting support part  20  has a larger pocket  25  for the installation of a gearwheel  26  and of a bevel pinion  27  of the low-speed gear stage of the speed-change gear mechanism. On the mounting support part  20  are located a large ring gear  28  for the low-speed gear and a small ring gear  29  for the high-speed gear. The ring gears  28 ,  29  are jointly connected in a rotationally secure and axially non-displaceable manner to the journal of the spindle  17 . The toothings of the ring gears  28 ,  29  point downward. The ring gear  28  meshes with the bevel pinion  27  seated below it on the transmission output shaft  12 . And the bevel pinion  21   b  of the pinion unit  21  engages from below in the ring gear  29 . 
     The short-length transmission output shaft  12  has a square cross section with a cylindrical bearing journal, can be easily inserted in a positive-locking manner into the gearwheel  26  connected to the bevel pinion  27  and, for the purpose of axial fixing, is pinned to a collar bushing. Axially parallel to the transmission output shaft  12  and above the ring gears  28 ,  29  there is disposed a hollow-shaft pinion  30 , which engages in the gearwheel  26 . The hollow-shaft pinion  30  is mounted on the rear side in the rear wall of the support outer tube, and supported coaxially in its hollow shaft is a longitudinally displaceable transmission input shaft  31 , which has its second mounting in a bearing flange sleeve  32  seated on the front side of the support outer tube  13 . 
     Located between the front end face of the hollow-shaft pinion  30  and a collar bushing  33  seated in the wall of the support outer tube  13  there is a gearwheel  34 , which is mounted loosely on the transmission input shaft  31  and belongs to the high-speed gear stage of the speed-change gear mechanism. In the bore of the gearwheel  34  there are two axial grooves  34   a , and the front region of the hollow-shaft pinion  30  has a cylindrical counterbore  30   a  and a continuous transverse slot  30   b , corresponding to the width of the axial grooves  34   a.    
     The transmission input shaft  31  has two radially protruding dogs  31   a , which, following appropriate axial displacement of the transmission input shaft  31 , can engage either in the axial grooves  34   a  or in the transverse slot  30   b  so as to be able to transmit the torque generated via a hinged crank handle  35  selectively to the high-speed gear or the low-speed gear stage of the speed-change gear mechanism. And if the dogs  31   a  are brought into the region of the counterbore  30   a  as an intermediate setting, a freewheel exists. 
     An axial locking of the transmission input shaft  31  against unwanted displacement during the cranking and to ensure that the manual drive mechanism, in motorized operation of a support pair, remains securely switched off, in the bearing flange sleeve  32  three radial grooves  32   a  are provided, into which a ball spring element  31   b  placed in the transmission input shaft  31  selectively engages. 
     In order to illustrate the working of the speed-change gear mechanism, in  FIG. 3  the power flow in high-speed gear is represented schematically in the form of arrowed lines. The dash-dot lines show the power take-off to the neighboring support. In the same way, the power flow in low-speed gear is shown in  FIG. 4 . 
     The support  10  according to the invention which is shown in  FIG. 5 , having a spindle  37  which is mounted in a bearing plate  36  and on which a ring gear  38  with two concentric toothings  38   a / 38   b  is seated, has an intermediate drive unit  39  for the high-speed gear and a gearwheel/bevel pinion unit  40  for the low-speed gear. The gearwheel/bevel pinion unit  40  consists of a gearwheel  40   a  and a bevel pinion  40   b  and is provided with a bearing journal  40   c , on which the intermediate drive unit  39  is mounted rotatably in the bearing bore  39   c . In the gearwheel/bevel pinion unit  40 , axially opposite its bearing journal  40   c , a transmission output journal  41  is inserted in a positive-locking and axially fixed manner, which also serves for the storage of said unit in the rear wall of the support  10 . 
     The intermediate drive unit  39  consists of a hollow shaft, a bevel gear  39   a  being seated on the open side thereof and a pinion  39   b  being disposed on the oppositely adjoining region. The end piece of the intermediate drive unit  39  serves for the mounting  42  of the same in the front region of the support outer tube  13 . The mounting  42  of the intermediate drive unit  39  is shaped such that, located in a cap  43 , it projects into the outer tube  13  of the support  10 . 
     On the transmission input shaft  31  there is a rotationally movable, large-diameter gearwheel  44  for the high-speed gear. The gearwheel  44  has on the inside, apart from axial grooves  44   a  for rotary transport by dogs  31   a  of the transmission input shaft  31 , also a cylindrical counterbore  44   b  for the freewheel setting of the dogs  31   a . The axial setting of the transmission input shaft  31  is represented in the high-speed gear setting. The force path in the high-speed gear setting is from the transmission input shaft  31  via the gearwheel  44  and the pinion  30   b  to the intermediate drive unit  39  and, via the bevel gear  39   a  thereof, to the toothing  38   b  of the ring gear  38  to the spindle drive (see arrow line in  FIG. 5 ). 
     At the same time, a part of the torque is transferred from the ring gear  38  via its toothing  38   a  to the bevel pinion  40   b , and via the transmission power take-off journal  41  and the connecting shaft  11  (see  FIG. 1 ) to the neighboring support (see dash-dot arrow line in  FIG. 5 ). In this embodiment of the support  10 , the hollow-shaft pinion  30  is provided on the end face of the hollow shaft merely with transverse slots  30   b , in which, after the transmission input shaft  31  has been switched over, its dogs  31   a  engage and the low-speed gear is realized in the manner described earlier. 
     In the support  10  shown in  FIG. 6 , in contrast to that shown in  FIG. 5 , the bevel gear  39   a  of the intermediate drive unit  39  is located on the other end region of its hollow shaft. In functional terms, this embodiment therefore advantageously differs from the semitrailer supports presently on the market by virtue of an opposite drive rotational direction of the high-speed gear and the low-speed gear. The direction of rotation of the crank handle  35  can namely be formulated in high-speed gear, i.e. without load when the support inner tube  13  is extended (let out), such that cranking can perforce easily be carried out counterclockwise. By contrast, the retraction (drawing-in) of the support inner tube  13 , at perforce higher necessary cranking pressure in the clockwise direction, can be cranked more comfortably. On the other hand, in low-speed gear, the extension of the support inner tube  13 , i.e. the raising of the load, can continue to be well realized, as previously, rotating in the clockwise direction. The power flow in high-speed gear is represented with arrow lines or dash-dot lines in  FIG. 6 . 
     In  FIG. 7 , a support  10  is shown in which, unlike in  FIG. 5 , the transmission output journal  41  is provided with a bearing journal  41   a , which is placed in a positive-locking manner partially in the gearwheel/bevel pinion unit  40  and on which, moreover, the intermediate drive unit  39  is rotatably mounted. The working is described as for  FIG. 5 . 
       FIG. 8  shows a support  10  according to  FIG. 5 , yet with an intermediate drive unit  39  which is fully cylindrical and has a second bearing journal  39   c , which is mounted rotatably in the gearwheel/bevel pinion unit  40  and the transmission output journal  41 . And the bevel gear  39   a  is mounted in a rotationally secure manner. The working is described as for  FIG. 5 . 
     The support  10  shown in  FIG. 9  has a gearwheel drive unit  45 , which has a gearwheel  45   a  and a pinion  45   b . The gearwheel drive unit  45  is on one side, seated on the transmission input shaft  31 , connected to this in a rotationally secure and axially coupled manner by pinning. And the other side of the gearwheel drive unit  45  is mounted in an axially displaceable manner on a bearing journal  46 , which is seated on the inner side of the rear wall of the support outer tube  13 . In high-speed gear of the support  10 , the gearwheel  45   a  of the gearwheel drive unit  45  meshes with the pinion  39   b  of the intermediate drive unit  39  and the power flow takes place according to the arrow lines included in  FIG. 9 . If the transmission input shaft  31 , for the purpose of shifting to the low-speed gear, is pushed in as far as possible, the pinion  45   b  of the intermediate drive unit  39  enters into engagement with the gearwheel  40   a  of the gearwheel/bevel pinion unit  40  and the power flow can then be realized according to the previously described embodiments. In an axial intermediate setting of the gearwheel drive unit  45 , the gearwheel  45   a  and the pinion  45   b  are disengaged, which corresponds to the neutral gearshift. 
       FIG. 9  additionally shows the bearing plate  36  in a cup-like configuration, in an edge region a recess  36   a  being provided, into which the gearwheel  40   a  extends. The edge of the cup-like bearing plate  36  is welded to the support outer tube  13 . The support inner tube  14  extends, in its transport setting which is shown here, to right up to the lower region of the edge of the cup-shaped bearing plate  36 . The nut  18  is fixed in the support inner tube  14  in a manner which is not shown. 
     Finally,  FIG. 10  shows an embodiment of the support, in which the transmission input shaft  31  disposed above the intermediate drive unit  39  of the high-speed gear is installed laterally offset from the intermediate drive unit  39  by, for example, a measure X.