Abstract:
The invention concerns a mobile crane with a long main boom. According to the invention, the main boom is in two parts linked at a swivel point in such manner that the boom can bend when raised and can be positioned in extended or quasi-extended final erection position.

Description:
BACKGROUND OF THE INVENTION 
   The invention concerns a mobile crane with an elongated boom. 
   Longer and longer booms are being required in special applications. The problem of raising very long booms arises particularly in connection with the erecting of wind generators. Booms of this type are usually raised with an extension derrick boom with attached derrick ballast. However, this is very time-consuming, and in the difficult terrain in which wind generators are often located it is very difficult to do. 
   Theoretically it is already known how to equip main booms with rocking grid tips. In rocking tips of this type, retainer devices must be provided. Furthermore, after the main boom is raised, they are usually in a bent position in relation to the main boom. 
   SUMMARY OF THE INVENTION 
   It is the task of the within invention now to permit the erecting of very long main booms without a derrick boom, whereby the entire erection procedure is made easier and in particular long main booms can be raised. 
   According to the invention, this task is performed by the following characteristics: the main boom is in two parts connected with each other at a swivel point in such manner that the main boom can be bent during erection in order to be moved into an extended or quasi-extended final erection position. This raised main boom does not require any retainer device. 
   Preferably there is on the main boom a special adaptor with at least one strut member that is positioned to swivel on a swivel point. This adaptor can be positioned at any desired location on the boom. 
   An outward-swiveling support can be jointed on the strut member. 
   The mobile crane can have an auxiliary coil off and on which an auxiliary guy can be wound. 
   Additionally, there can be an adjustment coil over which an adjustment strap can be drawn to the tip of the strut member, which it can be attached by means of a hook. 
   The adjustment strap can be drawn over this adjustment coil to raise the bent front section of the main boom. 
   Preferably, two strut members can be positioned parallel to each other. 
   The swivel axles of the two strut members can be positioned on an oblique in relation to the main boom, in which case by means of the oblique arrangement of the swivel axles of the two strut members a lateral guying can be achieved that further increases the lateral stability of the boom. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional details and advantages of the invention are explained in greater detail by means of the embodiment illustrated in the drawing, which shows: 
       FIG. 1 : A side view of a mobile crane according to the within invention, with a main boom still lying on the ground, 
       FIGS. 2 to 4 : Various working sections during the raising of the main boom in an embodiment as illustrated in  FIG. 1 , 
       FIGS. 5 to 7 : Details during the erection of the mobile crane. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a mobile crane  10  with a main boom  12  consisting of a lower boom segment  14  and an upper boom segment  16 , which are connected so as to swivel on a coupling point  18 . In  FIG. 1  the entire boom length of the main boom  12  is assembled on the ground. This main boom has a special adaptor that is equipped with a knee joint and a strut member and which is installed in the place of a standard adaptor. This adaptor can be installed at any desired point on the boom. 
   The assembly of the crane and the mobile crane  10  components necessary for the raising of main boom  12  are explained in greater detail by means of  FIGS. 5 to 7 . 
     FIG. 5  shows that there is a strut member on the upper segment of main boom  16 , which said strut member  20  can pivot on a coupling joint  22  toward upper boom  16 . When the main boom is raised, auxiliary crane  24  raises strut member  20  slightly out of transportation position, until a lever arm is created with respect to coupling joint  22 . By means of a fold-out support  26  the strut member  20  is held in this position. Two rollers  28  and  30  are positioned at the tip of strut member  20 . 
   There is on mobile crane  10  an auxiliary coil  32  over which an auxiliary guy  34  is drawn and led backward, as partially indicated by the dotted lines in  FIG. 5 , to a hoist  36 . Here auxiliary guy  34  is connected with a hoisting cable wound on the hoist. With auxiliary coil  32 , by means of auxiliary guy  34 , the hoist is pulled forward to attachment point  38  near the tip of upper segment  16  of main boom  12 . There the hoist is bolted to fixed point  38 . 
     FIG. 6  shows the raising of strut member  20 . Through the winding of the hoisting cable on hoist  36 , the strut member  20  is straightened independently and guys front anchoring rod  40 . An adjustment coil  42 , with which an adjustment strap  44  is coupled, is positioned on main boom  12 . Through the winding of an adjustment cable  46  off adjustment coil  42 , and the simultaneous winding up of hoist  36 , the upper adjustment pulley  48  is drawn to the tip of the strut member until a pin  50  at the upper adjustment pulley  48  engages in a hook  52  (compare  FIG. 7  and particularly Detail A on  FIG. 7 ). 
   For disassembly, hook  52  can be raised with a short auxiliary guy  54  (compare Detail A in  FIG. 7 ). The short auxiliary guy  54  is additionally connected with the long auxiliary guy  34 , so that the necessary force can be brought to bear on auxiliary coil  32 . 
   When the main boom is raised, as shown in  FIGS. 2 to 4 , the lower segment  14  of the main boom is raised first (compare  FIG. 2 ). The tip of the upper segment of boom  16  thereupon rolls on the ground, or is held in suspension with an auxiliary crane. During the raising of lower segment  14  of main boom  12 , adjustment strap  44  is continually slackened, so that the boom head weight lies on the ground and therefore does not have to be raised with lower segment  14 . After the lower segment of the main boom has reached an appropriate angle to the ground, with consequent displacement of the loads closer to the crane, upper segment  16  of the main boom is pulled up by the pulling of the adjustment strap  44  by means of adjustment coil  42 . The main boom is still inclined forward, so that the boom can be moved into an extended position without any need for a retainer device. The boom is drawn up to a stop device and adjustment strap  44  is secured. The stability of boom  10  is further increased by means of this additional guying.