Abstract:
A level-controllable crawler crane includes two crawler supports with rotating crawlers, which crawler supports are connected by a transversal bridge. A superstructure of the crawler crane includes a crane jib pivotable about a vertical axis and connected to the transversal bridge. A pivotable articulation connects the transversal bridge to the crane superstructure. At least one of the crawler supports is connected to the transversal bridge by a double link having a lower and an upper link. The lower link is articulated on the crawler support by a crawler support lower pivotable axis and on the transversal bridge by a transversal bridge lower pivotable axis. The upper link is articulated on the crawler support by a crawler support upper pivotable axis and on the transversal bridge by a transversal bridge upper pivotable axis. A drive pivots the links about the pivotable axis associated therewith.

Description:
FIELD 
       [0001]    The invention relates to a crawler crane according to the precharacterizing portion of claim  1 . The invention furthermore relates to a method for fine-tuning a basic operating position of such a crawler crane. 
       BACKGROUND 
       [0002]    A crawler crane of the type mentioned at the beginning is known from DE 20 2006 002 023 U1. Booms of such crawler cranes can operate at their nominal load only when the undercarriage with the crawler supports is positioned on a plane that virtually does not deviate from the horizontal. This requires a time-consuming and expensive preparation of a basic operating position of the known crawler crane through grading operations. 
       SUMMARY 
       [0003]    It is an aim of the present invention to improve a crawler crane of the type mentioned at the beginning in such a way that the amount of time and expense required for fine-tuning a basic operating position of the crawler crane is reduced. 
         [0004]    This aim is achieved according to the invention by a crawler crane having two crawler supports having rotating crawlers, at least one transversal bridge connecting the two crawler supports, a crane structure having at least one crane boom connected to the transversal bridge so as to be able to pivot about a vertical axis, a pivot articulation that pivotally connects the transversal bridge to the crane superstructure, characterized in that at least one of the crawler supports is connected to the transversal bridge via a double link comprising a lower link that is articulated via on the crawler support a crawler-support lower pivot shaft and on the transversal bridge via a transversal-bridge lower pivot shaft, an upper link that is articulated on the crawler support via a crawler-support upper pivot shaft and on the transversal bridge via a transversal-bridge upper pivot shaft, an adjustment drive for pivotally displacing at least one of the two links about the pivot shaft assigned to same. 
         [0005]    In accordance with the invention it has been recognized that an undercarriage of the crawler crane with the two crawler supports in many cases can be set up in such a way that it has virtually no pitch inclination about a horizontal axis transverse to the driving direction, but only a roll inclination about an axis longitudinal to the driving direction. This roll inclination can be compensated via the double link according to the invention. The adjustment drive can be designed to be motor-driven, hydraulic or magnetic. It is also possible in principle to not equip the adjustment drive with an adjustment motor of its own, but to drive the adjustment movement, for example, derived from another motor of the crawler crane or also from an external motor. In principle, a single such double link suffices, the other connections of the crawler supports to the at least one transversal bridge then being capable of being repositioned passively. It is preferred, however, when a plurality of such double links are used. It is also possible, for example, to provide per crawler support a plurality of such double links arranged one after another in the driving direction. The adjustment drive can be designed compact with high power density and robustness. 
         [0006]    An arrangement according to the claims in which both crawler supports are connected to the transversal bridge via a double link having a lower link and an upper link, increases the stability of the crawler crane. 
         [0007]    A plurality of drive-adjustable double links of both crawler supports according to the claims, which have an adjustment drive for pivotally displacing at least one of the two links about the crawler-support pivot shaft assigned to same, improve the fine-tuning precision of a level control of the crawler crane. 
         [0008]    A lower-link adjustment drive according to the claims in which the lower link is connected to the adjustment drive lowers the center of gravity of the crawler crane. A pivot shaft that is driven via the adjustment drive is then, in particular, the crawler-support lower pivot shaft. 
         [0009]    The adjustment drive which has, according to the claims, a gear unit, in particular a reduction gear, facilitates the connection and, if applicable, also the design of the adjustment motor. 
         [0010]    A gear unit according to the claims in which at least three gear wheels are provided that are in combing engagement with one another, the axes of rotation of which are parallel to one another, can increase a distance between a motor shaft of the adjustment motor and a component of the double link driven by same, thereby simplifying the design of the double link. 
         [0011]    An adjustment drive according to the claims which has a threaded rod connected to the crawler support and a nut connected to the driven link, the nut being complementary to the thread of the threaded rod is robust. The nut can be designed self-locking. This self-locking behavior can be combined with a sensitive adjustability, thereby permitting a precise inclination fine-tuning or leveling capability to be achieved. Through the design of the adjustment drive with the threaded rod and the nut, it is possible to derive from the rotational adjustment drive a translational, low-backlash movement for an inclination fine-tuning, the movement monitoring of which is possible in a simple manner. 
         [0012]    A threaded rod, which according to the claims has a trapezoidal external thread and the nut which has a trapezoidal internal thread complementary thereto results in a self-locking of the adjustment drive. Additionally, such a trapezoidal thread has a high load-bearing capacity. 
         [0013]    A driven threaded rod according to the claims in which the threaded rod is driven by the adjustment drive makes possible an adjustment drive, the design of which can be implemented with little time and expenditure. 
         [0014]    A control device according to the claims is provided that is in signal connection with the at least one adjustment drive, which permits the adjustment drive to be activated in particular from a cab of the crawler crane. 
         [0015]    An inclination sensor according to the claims is provided that is in signal connection with the control device, which makes possible a precise inclination measurement. The inclination sensor can be a contactless magnetoresistive measuring element having a measuring range of +/−10%. 
         [0016]    A regulating module according to the claims is provided that is in signal connection with the control device and with the inclination sensor and provides to the control device positioning signals for adjusting the adjustment motor in such a way that if a roll inclination of a foot print plane of the crawler support is present, the vertical axis of the crane structure assumes a minimal angle relative to the vertical, makes possible an automatically regulated adjustment of the adjustment drive for level control of the upper structure of the crawler crane. 
         [0017]    A linear guiding mechanism according to the claims in which the nut is connected via a linear guiding mechanism to the driven link makes possible a guided transmission of force between the nut and the driven link, while simultaneously creating the possibility of a high force transmission between the nut and the driven link. The linear guiding mechanism can be implemented by means of a plurality of bearing rollers. A bearing support for the linear guiding mechanism can be provided on both sides of the nut. The linear guiding mechanism can support the nut in both directions of movement longitudinal to the threaded rod. 
         [0018]    The advantages of a method according to the claimed invention correspond to those that have already been discussed above with reference to the crawler crane according to the invention. The adjustment of the adjustment drive can be effected automatically regulated. This can be achieved, for example, by using the measured value from an inclination sensor, such that the crane structure of the crawler crane maintains its basic operating position within a predefined permissible variation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    An illustrative embodiment of the invention will be explained in more detail below in conjunction with the drawing, in which: 
           [0020]      FIG. 1  shows a side view of a crawler crane; 
           [0021]      FIG. 2  shows a front view of an undercarriage of the crawler crane according to  FIG. 1  together with components of a crane structure of the crawler crane, certain boom elements of the crawler crane having been left out; 
           [0022]      FIG. 3  shows a vertical section through a crawler support of the crawler crane in the area of a double linkage thereof to a transversal bridge of the undercarriage represented by a broken line, a crawler of the crawler support being shown positioned on a horizontally extending ground surface; 
           [0023]      FIG. 4  shows the crawler support with the transversal bridge and the crawler in an illustration similar to  FIG. 3 , with the crawler shown positioned on an inclined ground surface, such that a roll angle of the undercarriage results that is different from zero; 
           [0024]      FIG. 5  shows a detail view of a section of the crawler support from the direction V in  FIG. 3 ; 
           [0025]      FIG. 6  shows, in even greater detail than  FIG. 5 , a nut as a component of an adjustment drive for pivotally displacing a lower link of the undercarriage and thereby for a level-controlling of the crawler crane; 
           [0026]      FIG. 7  shows an axial section through the adjustment drive in the area of the connection of the nut according to  FIG. 6  to a rotationally driven threaded rod of the adjustment drive; and 
           [0027]      FIG. 8  shows a section along line VIII-VIII in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    A crawler crane has a mobile undercarriage  2 , an upper structure  3 , a main crane boom  4  and a counter-boom  5 . The upper structure  3  can rotate relative to the undercarriage  2  about a vertical axis  7  by means of a roller slewing ring device  6 , which is only intimated in  FIGS. 1 and 2 . 
         [0029]    The undercarriage has two driven crawlers  8  that are supported and guided by means of two crawler supports  9  that are arranged parallel to one another. The two crawler supports  9  are connected to one another by means of a transversal bridge  10  or by means of a plurality of such transversal bridges. The at least one transversal bridge  10 , in turn, carries the roller slewing ring device  6 . The roller slewing ring device  6  is a pivot articulation that connects the at least one transversal bridge  10  in a pivot-mounted fashion to the upper structure  3 , that is to say to the crane structure. 
         [0030]    The at least one transversal bridge  10  is connected at the two ends thereof to the respective crawler support  9  via a double link  11 , which is illustrated in detail in  FIGS. 3 to 5 . The double link  11  has a lower link  12  that is articulated on the crawler support  9  via a crawler-support lower pivot shaft  13  and on the transversal bridge  10  via a transversal-bridge lower pivot shaft  14 . Additionally, the double link  11  has an upper link  15  that is articulated on the crawler support  9  via a crawler-support upper pivot shaft  16  and on the transversal bridge  10  via a transversal-bridge upper pivot shaft  17 . 
         [0031]    Both the lower link  12  and the upper link  15  have two identically contoured link plates that are arranged spaced apart one behind the other in the drawing plane of  FIGS. 3 and 4  and fixedly connected to one another via shaft elements. The upper link  15  is reminiscent in the shape thereof of a chain link of a bicycle chain. 
         [0032]    If a plurality of cross members  10  are present in the crawler crane  1 , each cross-member end is connected to the facing crawler support  9  by means of such a double link  11 . 
         [0033]    The pivot shafts  13 ,  14 ,  16 ,  17  all extend parallel to one another and parallel to a foot print plane  18  that is defined by a bottom tread  19  of the crawler  8  resting on the ground. In  FIGS. 2 and 3  the foot print plane  18  extends horizontally. The crawler crane  1  and in particular also the crawler supports  9  then neither have a roll inclination nor a pitch inclination. In this non-inclined position of  FIGS. 2 and 3 , the two lower pivot shafts  13  and  14  of the double link  11  are on approximately the same level. The transversal-bridge upper pivot shaft  17  is slightly lower in this position than the crawler-support upper pivot shaft  16 . In this position the crawler-support upper pivot shaft  16  lies vertically above the crawler-support lower pivot shaft  13 , and the transversal-bridge upper pivot shaft  17  lies vertically above the transversal-bridge lower pivot shaft  14 . The mutual distance between the two lower pivot shafts  13 ,  14  is virtually equal to the mutual distance between the two upper pivot shafts  16 ,  17 . The mutual distance between the two crawler-support pivot shafts  13 ,  16  also is approximately equal to the mutual distance between the transversal-bridge pivot shafts  14 ,  17  and corresponds to the distance between the lower pivot shafts  13 ,  14  and the upper pivot shafts  16 ,  17 . 
         [0034]    Altogether, the four pivot shafts  13 ,  14 ,  16 ,  17  in the position according to  FIGS. 2 and 3  therefore lie approximately in the corners of a square. 
         [0035]    An adjustment drive  20  having an adjustment motor  21  serves for pivotally displacing the lower link  12  about the crawler-support lower pivot shaft  13  and thereby for a level-controlling of the crawler crane  1  to be described further below. Each of the double links  11  of the crawler crane  1  can have such an adjustment drive  20 . 
         [0036]    The adjustment drive  20  has a threaded rod  22  that extends perpendicular to the foot print plane  18  and is connected to the crawler support  9  by means of an axial/radial bearing  23  fixedly connected to the crawler support, in a manner so as to be able to rotate about the longitudinal axis of the threaded rod  22 . The threaded rod  22  has an external thread that is designed in the form of a trapezoidal external thread. A nut  24  that is connected to the lower link  12  in a manner so as to be unable to rotate relative to the crawler support  9 , by means of connecting pieces  25  that define a parallel key guidance runs on the threaded rod  22 . The nut  24  has a trapezoidal internal thread that is complementary to the external thread of the threaded rod  22 . 
         [0037]    The nut  24  is connected to a lever end  26  of the lower link  12 , the lever end being located opposite the transversal-bridge lower pivot shaft  14 . The crawler-support lower pivot shaft  13  lies between the lever end  26  and the transversal-bridge lower pivot shaft  14 . 
         [0038]    The adjustment motor  21  drives a rotation of the threaded rod  22  about the longitudinal axis thereof by means of a gear unit  27  that is designed in the form of a reduction gear. The gear unit  27  has three gear wheels  28 ,  29 ,  30  that are in combing engagement with one another. The first gear wheel  28  is connected to a drive shaft  31  of the adjustment motor  21  so as to be integral in rotation with the drive shaft. The second gear wheel  29  serving as an intermediate gear is connected by means of an axial/radial bearing  32  to the crawler support  9 . The third gear wheel  30  is connected to the threaded rod  22  so as to be integral in rotation therewith. The number of teeth of the second gear wheel  29  is greater than the number of teeth of the first gear wheel  28 . The number of teeth of the third gear wheel  30  is greater than the number of teeth of the second gear wheel  29 . 
         [0039]    The adjustment motor  21  is in signal connection with a control device  34  of the crawler crane  1  via a signal line  33 . Connected to the control device  34  via an additional signal line  35  is an inclination sensor  36  which, in turn, is mounted fixedly to the crawler support  9  and reads a roll inclination of the crawler support  9 , that is to say an inclination of same about an axis extending longitudinal to the driving direction. The control device  34  can have a regulating module  37  which likewise is in signal connection with the inclination sensor  36 . The regulating module  37  is designed as an internal component of the control device  34 . Alternatively, the regulating module  37  can also be an external component that is in signal contact with the control device  34 . 
         [0040]      FIG. 4  shows a level-controlled position of the transversal bridge  10  at a foot print plane  18  of the crawler support  9  that is inclined relative to a horizontal. A roll angle W between the foot print plane  18  and the horizontal is 4°. In this inclined position of the crawler support  9  a level control of the transversal bridge  10  is ensured by means of the double link  11  such that a transversal-bridge plane  38  and therefore also the upper structure  3  has no roll inclination (W=0°) relative to the horizontal. 
         [0041]    In the position according to  FIG. 4  the pivot shafts  13 ,  14 ,  16 ,  17  assume approximately the positions of the corners of a rhombus. The double link  11  thus has performed a parallelogram pivot movement from the position according to  FIG. 3  to the position according to  FIG. 4 . 
         [0042]    In order to fine-tune a basic operating position of the crawler crane  1  the undercarriage  2  is first moved into a raw operating position. This raw operating position is selected such that the crawler crane  1  has no pitch inclination, that is to say no inclination of the foot print plane  18  relative to the horizontal about an axis extending transversely to the driving direction. Then, only the roll inclination needs to be compensated via the level control. The roll angle W of the respective crawler support  9  relative to the vertical is then measured with the aid of the inclination sensor  36 . This roll inclination is communicated via the signal line  35  to the control device  34 . The regulating module  37  calculates, for example via a calibration table, from the determined roll inclination a positioning value for the adjustment motor  21 . This positioning value is supplied to the adjustment motor  21  via the signal line  33 . A rotational displacement of the threaded rod  22  by the adjustment drive  20  is effected accordingly in such a way that the nut  24  assumes on the threaded rod  22  an axial position that corresponds to a predefined angle of pivot of the lower link  12  about the crawler-support lower pivot shaft  13 . According to this pivot angle the double link  11  moves into a level-controlled position in which the transversal bridge plane  38  extends substantially horizontal despite the roll inclination of the crawler support  9  by the roll angle W. This ensures a minimal angle of the vertical axis  7  of the upper structure  3  relative to the vertical, such that the main crane boom  4  can support the nominal load thereof in a weight-balanced manner. 
         [0043]    The adjustment of the adjustment drive  20  for the level control of the upper structure  3  can take place automatically regulated via the regulating module  37 . Alternatively, it is possible for the inclination sensor  36  to, for example, read a roll angle and for the operator of the crawler crane  1  to carry out an appropriate fine-tuning of the double link  11  based on this roll angle via the control device  34 . 
         [0044]    Further details of the adjustment drive  20  for pivotally displacing the lower link  12  will be explained below in conjunction with  FIGS. 6 to 8 . 
         [0045]      FIG. 6  shows the nut  24  in detail. The nut transforms the rotary motion of the driven threaded rod  22  into a linear movement longitudinal to the threaded rod  22  (cf. double arrow  39 ). This linear movement  39  is then transmitted to the lower link  12  by means of a guiding mechanism to be described further below. 
         [0046]    The nut  24  comprises a thread carrier  40 , a thread insert  41  and a pair of bolts  42 ,  43 . 
         [0047]    The thread carrier  40  has an inner boiler plate  44  and an outer boiler plate  45  that surround the thread insert on the outside. The boiler plates  44 ,  45  each have bores  46  for accommodating the bolts  42 ,  43 . The boiler plates  44 ,  45  are held together both by a bottom sheet-metal ring  47  and a top sheet-metal ring  48 . The bottom sheet metal ring  47  has an outer circumference that corresponds to the outer circumference of the outer boiler plate  45 . The bottom sheet-metal ring  47  therefore is flush on the outside with the outer boiler plate  45 . An inside diameter of the bottom sheet-metal ring  47  is slightly larger than the internal thread diameter of the thread insert  41 , such that the thread insert  41  rests on the bottom sheet-metal ring  47 . Toward the inside, the inner boiler plate  44  has guiding ribs, which are not shown in the drawing. Complementary to these guiding ribs, an outer wall of the thread insert  41  has guide grooves extending in an axial direction, that is to say in the direction of the axis  49  of  FIG. 6 . This complementary connection represents an anti-rotation locking mechanism of the thread insert  41  relative to the thread carrier  40  about the axis of rotation  49 . 
         [0048]    The top sheet-metal ring  48  has an outside diameter that corresponds to the outside diameter of the outer boiler plate  45 . The top sheet-metal ring  48  therefore is flush toward the outside with the outer boiler plate  45 . The top sheet-metal ring  48  has internal threads  50  that extend in an axial direction, that is to say parallel to the threaded rod  22  in the assembled state of the sheet metal ring  48 , into which internal threads self-locking bolts  51  are screwed. A collar piece of a locking plate  51   a  is fixed between heads of the self-locking bolts  51  and the top sheet-metal ring  48 . The locking plate  51   a  locks in place the axial position of the thread insert  41  relative to the thread carrier  40 . 
         [0049]    The thread carrier  40  accommodates the thread insert  41  and locks same in place. Additionally, it transmits the force from the thread insert  41  to the bolts  42 ,  43 . 
         [0050]    The thread insert  41  is made of bronze. 
         [0051]    The bolts  42 ,  43  have a cross-sectional step that subdivides each bolt  42 ,  43  into an inner bolt section, which is arranged adjacent to the thread insert  41 , and an outer bolt section. The inner bolt section has a smaller outside diameter than the outer bolt section of the bolts  42 ,  43 . The bolts  42 ,  43  are inserted with the inner bolts sections thereof into the bores  46  of the boiler plates  44 ,  45 . A sleeve  52  is arranged in each case between these bores  46  and the inner bolt section. Surrounding and resting against the outer bolt sections of the bolts  42 ,  43  in each case is first a sleeve  53  and surrounding the sleeve  53  in each case is a guiding body  54 . 
         [0052]    The sleeves  53  are pressed into the guiding bodies  53  surrounding same and secured on the respective bolts  42 ,  43 . Serving this purpose in each case are locking rings. A wearing disk  55  is inserted between the thread carrier  40 , that is to say the outer boiler plate  45 , and the outer end wall of the sleeve  52  on one hand and an inner end section of the sleeve  53  on the other hand. On rotational displacement of the guiding body  54  relative to the thread carrier  40  about a bolt axis  56  extending horizontally in  FIG. 6  a defined wear and tear is effected there owing to the wearing disk  55 . 
         [0053]    In the movement that is driven by the adjustment drive  20  the lower link  12  is pivoted about the crawler-support lower pivot shaft  13 . The lever end  26  of the lower link  12  thus performs a circular arc-shaped motion of travel. The nut  24  connected to the lever end  26 , in turn, performs a linear movement longitudinal to the threaded rod  22 . The lever end  26  accordingly cannot be connected fixedly to the nut  24 . The transmission of force between the nut  24  and the lever end  26  is effected by means of a guiding mechanism  57 , details of which are shown in  FIGS. 7 and 8 . The guiding mechanism  57  is a linear guiding mechanism and is designed in the form of a roller-type connection. A top end wall  58  and a bottom end wall  59  of the guiding body  54  each run on a roller unit  60 ,  61  of the guiding mechanism  57 . Each of the roller units  60 ,  61  has a plurality of bearing rollers  62 , six in each case in the presented embodiment. The bearing rollers  62  of the top roller unit  60  are supported in a top bearing cage  63  and the bearing rollers  62  of the bottom roller unit  61  are supported in a bottom bearing cage  64 . The bearing cages  63 ,  64  are fixedly connected to the lever end  26  of the lower link  12  via holding components  65  that are wedge-shaped in the section of  FIG. 7 . 
         [0054]    When the lever end  26  is shifted longitudinally to the threaded rod  22  for pivotally displacing the lower link  12 , this goes hand in hand, in particular near the top and bottom end of the total pivot range, with a linear relative movement of the guiding body  54  relative to the bearing cages  63 ,  64  longitudinal to a direction of movement marked in  FIG. 8  with a double arrow  66 . The guiding mechanism  57  ensures that this relative movement takes place in a guided manner, at the same time enabling a very high force to be transmitted between the guiding body  54  and the roller units  60 ,  61 , and via same and the holding component  65  to the lever end  67 . At the same time the guiding body  54  is rotationally displaced about the central bolt axis  56  during this movement.