Abstract:
The invention relates to a method of operating a crane having a luffable crane boom and having a trolley travelable at the crane boom, wherein the crane can be operated in a luffing mode, on the one hand, and in a trolley mode, on the other hand. In accordance with the invention, a switch is made between a luffing mode and a trolley mode by varying the hoist rope reeving. The invention further relates to such a crane for carrying out the method.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a U.S. National Phase of International Patent Application Serial No. PCT/EP2013/002816, entitled “METHOD OF OPERATING A CRANE AND CRANE,” filed on Sep. 18, 2013, which claims priority to German Patent Application No. 10 2012 018 392.5, filed on Sep. 18, 2012, the entire contents of each of which are hereby incorporated by reference in their entirety for all purposes. 
     TECHNICAL FIELD 
     The invention relates to a method of operating a crane having a luffable crane boom and having a trolley arranged travelable at the crane boom, wherein the crane can be operated in a luffing mode, on the one hand, and in a trolley mode, on the other hand. The invention further relates to a crane which selectively allows a crane operation in trolley mode or in luffing mode. 
     BACKGROUND AND SUMMARY 
     Various crane systems are known from the prior art which offer certain advantages depending on the field of application. Revolving tower cranes having trolley booms are thus known in which the boom always adopts a horizontal position and in which the load can be traveled over the total boom length with the aid of a trolley. This provides the advantage that the suspended load can be moved particularly close to the tower. 
     In contrast, there are tower cranes having luffing booms which are also called variable booms. The luffing boom is fastened by a joint to the crane tower beneath the tower top and is variable in height via a boom guy rope. Such cranes do not have a trolley; the load is transported in the boom direction solely via the lifting and lowering movement of the boom. The named crane design above all provides advantages with tight space requirements since the boom can simply be “retracted” to avoid collisions with obstacles. In addition, the load can be raised to greater heights due to the steeper boom position. 
     An increasingly high degree of flexibility is in particular expected of mobile construction cranes which have a travelable, full-fledged revolving tower crane with a trolley boom. This crane structure is frequently intended to operate under complex spatial conditions at the construction site so that the aforesaid advantages of the luffing boom system are of great interest. 
     In the past, it has already been endeavored to merge the two proposed crane systems with one another. The advantages of the two different crane systems should in particular be combined in a single crane system. 
     A revolving tower crane is known from DE 1 171 132, for example, which has a retractable boom and a trolley guided thereat. The trolley is latched to the tip of the boom for the operation as a luffing boom. Any desired incline is hereby allowed for the boom system without the trolley leaving its position at the tip. 
     The support of the trolley at the boom tip, however, increases the unladen weight torque of the boom system and consequently reduces the possible peak payload in luffing operation. In addition, hoist rope length is lost due to the reeving of the hoist rope which can actually be needed with steep boom positions. 
     It is the object of the present invention to provide a crane or a method of operating a crane with which the initially named problem can be overcome. 
     This object is achieved by a method of operating a crane in accordance with the features of claim  1 . Advantageous embodiments of the method in accordance with the invention are the subject of the subordinate claims dependent on the main claim. 
     Claim  1  therefore proposes a method of operating a crane having a luffable crane boom and having a trolley travelable at the crane boom. The crane configuration on the one hand allows crane operation in the luffing mode and on the other hand an operation in the trolley mode. The crane operator can selected the ideal crane mode based on the application and can convert the crane between the individual modes by carrying out the method. 
     The crane is, for example, configured as a revolving tower crane, in particular as a mobile construction crane, which comprises a luffing boom having a travelable trolley. 
     Previously known designs from the prior art propose fastening the trolley to the boom tip for the luffing mode and to let off the crane hook from the trolley. The present invention now takes a path which differs in decisive points. In accordance with the invention, the reeving of the hoist rope at the boom system is varied so that a luffing operation of the crane is made possible. The deflection of the hoist rope from the boom to the crane hook thus takes place independently of the trolley. 
     The re-reeving above all opens up the possibility of positioning the trolley at any desired position of the crane boom during the luffing operation. A support at the boom tip is no longer absolutely necessary, from which certain advantages result. For example, a positioning of the trolley close to the tower can have a favorable effect on the unladen weight torque of the crane. 
     Furthermore, not only an increase in the peak payload can be achieved during the luffing mode by a favorable choice of the fixing position, but also an increase in the effective crane outreach. The travel path of the trolley to the boom tip is limited as a rule by the technical circumstances so that the theoretically maximum outreach of the crane could not be ideally exploited either in the trolley mode or in the luffing mode. Due to the re-reeving in accordance with the invention, this disadvantage can be avoided during the luffing mode and the effective crane outreach can be increased. 
     It has been found to be particularly advantageous if, due to the re-reeving, a change is made between a single-line operation in the luffing mode and a multi-line operation, in particular a dual-line operation, in the trolley mode. Due to the re-reeving of the hoist rope into a single-line operation, additional hoist rope length can be gained which is in particular advantageous with steep boom positions in the luffing mode. 
     The hoist rope is beaten up to the boom system at the end side during the trolley mode. To change the reeving, it may be advantageous for the fixing point of hoist rope to be released for the crane operation in luffing mode and for it to be beaten up to a lifting hook or to be latched thereto. The crane is then operated in single-line operation. It is particularly expedient if a separate lifting hook is available for the luffing mode. 
     In a particularly advantageous embodiment, the trolley and/or the used crane hook/hook block of the trolley mode is latched to the boom or to the trolley for operation in the luffing mode. Since the latching of the trolley does not necessarily have to take place at the boom tip in the present invention, a latching positions is selected which is ideal with respect to the unladen weight of the trolley, which is expediently spaced apart from the boom tip and which reduces the unladen weight torque at the boom tip. A latching of the trolley close to the pivot connection point of the boom is particularly advantageous. 
     In this case, it can be advantageous to use an anyway present transport position or dismantling position for the trolley to latch it to the boom during the luffing mode. This transport position or dismantling position for the trolley is as a rule arranged in the region of the boom pivot connection point. 
     It is expedient in an advantageous embodiment of the invention to use a rope reeving pulley provided during the trolley mode as a deflection pulley during the luffing mode. The rope reeving pulley is as a rule arranged at the boom tip and serves the fixing or support of the hoist rope at the boom tip during the trolley mode. It is conceivable that the position of the rope reeving pulley for the luffing mode is directly spatially varied to be able to ensure an ideal deflection of the hoist rope. 
     It is of advantage for the re-reeving for the boom tip to be let down close to the ground. In this case, the re-reeving can be carried out comfortably and without any great effort from the ground by the crane operator. The boom tip is preferably let down close to the ground with an extended boom. 
     It is expedient for the re-reeving process with a let-down boom to secure the hoist rope to one or more securing means at the crane boom for safety reasons. The securing is preferably made before or shortly after the release of the fixing point of the hoist rope to the boom system. The hoist rope is released again before taking up the desired crane operation. 
     A fast and simple possibility can preferably be provided for a variable attachment of one or more additional elements to the boom, in particular to the boom tip. One or more boom elements can in particular be mounted to extend the boom to increase the useful boom length. The integration of other boom elements which provide additional functions at the boom system is, however, likewise conceivable. For example, individual elements or apparatus for the display of information can be attached to the boom tip. A combination of these elements with boom extensions is likewise conceivable. 
     The integration of one or more boom elements is facilitated by the letting down of the boom tip close to the ground. The boom can also be extended specifically for the luffing mode, which is not possible in the named fast and simple manner without any further effort in known trolley boom cranes due to the complexity of the trolley construction. 
     If one or more boom elements are mounted at the boom tip for the luffing mode, the hoist rope fixing point is released and is pulled out with the aid of a securing rope up to one of the additional boom elements, in particular up to the tip of the outer additional boom element. The securing rope is preferably guided from the outer tip of the outermost additional boom element up to the hoist rope fixing point for this purpose. 
     For the luffing mode, the hoist rope is expediently deflected by a deflection pulley attached to the additional boom element and is connected at the end side to the corresponding crane hook. 
     It is particularly advantageous if the rope reeving pulley is dismantled at the original boom during the trolley mode and is mounted at the corresponding additional boom element for the deflection of the hoist rope. 
     The hoist rope fixing point is preferably pulled up to the tip of the at least one additional boom element using a hand winch. 
     One or more sensors can detect the spatial geometry of the current crane configuration and can thus automatically recognize the planned crane mode, that is the luffing mode or trolley mode. The crane control can consequently work while taking account of the recognized crane mode and can release or carry out corresponding crane commands or functions. 
     The invention further relates to a crane, in particular to a revolving tower crane or to a mobile construction crane, having a luffable crane boom, in particular a luffing boom, and having a trolley arranged travelable at the crane boom. The proposed crane configuration allows the crane to be operated in a luffing mode, on the one hand, and in a trolley mode, on the other hand. 
     In accordance with the invention, the hoist rope of the crane is guided in the luffing mode via at least one deflection pulley at the crane boom, in particular at the boom tip, and is beaten up at the end side to a load hook or is latched thereto. The crane is characterized in accordance with the invention in that a one-line operation of the hoist rope is ensured during the luffing mode, whereas a multiple reeving of the hoist rope is necessary as a rule during the known trolley mode. 
     Certain advantages result from the single-line routing of the hoist rope during the luffing mode. For example, the position of the trolley is insignificant for the function of the crane in the luffing mode; a positioning close to the boom pivot-connection point is therefore possible. A larger hoist rope quantity is furthermore available by the single-line operation. 
     The crane in accordance with the invention advantageously moreover comprises means for carrying out the method in accordance with the invention or an advantageous embodiment of the method in accordance with the invention. The advantages and properties of the crane in accordance with the invention obviously correspond to those of the method in accordance with the invention so that a repeat description will be dispensed with at this point. 
     Further advantages and properties of the invention result from an embodiment described in more detail in the following drawings. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG. 1  shows a schematic side view of the crane in accordance with the invention during the trolley mode. 
         FIG. 2  shows a schematic side view of the crane in accordance with  FIG. 1  in the luffing mode. 
         FIG. 3A  shows a schematic side view of the crane in accordance with  FIG. 2  with an extended boom tip. 
         FIG. 3B  shows a detailed view of elements of  FIG. 3A . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a side view of the boom system of the crane in accordance with the invention. A luffing boom  30  is luffably pivotally connected to the head of the crane tower  10  about a horizontal luffing axis via a joint  20 . A boom guying rope  70  extends from the crane tower  10  via the crane tip up to the boom  30  for adjusting the luffing angle. The boom  30  can be adjusted in the vertically extending luffing plane by actuating the boom guying rope  70 . 
     The crane construction shown allows the crane operation in the luffing mode, that is with a luffable boom  30 , and also trolley operation. The hoist rope  40  is used for both modes. The trolley  60 , which can travel relative to the boom  30  in the latter&#39;s longitudinal axis, is available for the trolley mode. A respective rope pulley pair  62 ,  62   b  is arranged at the trolley  60  and at the hook block  61 , whereby a two-line operation of the hoist rope during the trolley mode is made possible. 
     A trolley drive which comprises the two driven rope pulleys  63  and the associated rope arrangement  64  is provided for traveling the trolley  60 . 
     The hoist rope  40  extends from the tower base via the boom pivotal connection point up to the boom tip. In the boom pivotal connection region, the hoist rope is guided via the rope pulley  51  and extends horizontally beneath the boom  30  in the direction of the boom tip. As already described, the hoist rope  40  is guided by the rope pulley pairs  62   a ,  62   b  of the trolley  60  or of the hook block  61  until it is deflected at the boom tip by the rope reeving pulley  80  and is fixedly connected to the boom structure at the end side in the region of the boom tip. The view X shows a front view of the boom tip. The rope reeving pulley  80  is pivotably connected to the boom tip via an axle  82  extending in parallel with the longitudinal boom axis. 
     The representation in accordance with  FIG. 2  shows the crane configuration which is operated during the luffing mode. The trolley  60  is fixed for this purpose at the anyway provided transport or dismantling latch position  130  and is held against a travel movement in the longitudinal axial direction of the boom  30 . The hoist rope fixing point is released in the region of the boom tip with respect to the crane configuration of  FIG. 1 . The end of the hoist rope  40  is connected to a hook block  90  provided for the luffing operation or is latched thereto. The hoist rope  40  is admittedly still guided by the deflection pulleys  62   a ,  62   b  of the trolley  60  or of the hook block  61 ; however, this has no influence on the crane operation in the luffing mode. 
     In the region of the boom tip, the reeving pulley  80  is used as a deflection pulley to deflect the hoist rope at the boom tip to the hook block  90 . The view X of  FIG. 2  likewise shows a front view of the boom tip. The rope reeving pulley/deflection pulley  80  hangs perpendicular at the boom tip with a horizontally extending axis of rotation. 
     The trolley is not latched to the boom tip, but rather in a position, which is favorable with respect to its weight, further inwardly close to the tower  10 , which results in an increase in the maximum crane payload. The crane operation is switched from a two-line operation in the trolley mode into a single-line operation in the luffing mode by the re-reeving of the hoist rope  40  for the luffing mode. Additional hoist rope length hereby becomes free, which is in particular of advantage with great hook heights having a steep boom position. 
     The effective outreach of the crane during the luffing mode can moreover be maximized with respect to trolley operation. As the dashed contours in  FIG. 2  indicate, the trolley  60  cannot be completely traveled up to the boom tip due to the technical circumstances. The maximum possible outreach of the trolley  60  or of the crane hook  61  is smaller by the spacing ΔL from the boom tip. 
     The hoist rope  40  is deflected directly at the boom tip with the aid of the deflection pulley  80  by the change of the crane configuration in the luffing mode, whereby an outreach gain of ΔL is achieved. The system-induced loss of effective outreach during the trolley mode is consequently avoided in the luffing mode. 
     The following individual method steps are required for the change of the crane configuration starting from the trolley mode to the luffing mode: 
     Initially, the crane hook  90  for the luffing mode is set at the target destination at the ground still during the trolley mode. Subsequently, the trolley  60  and its hook  61  are latched at the boom  30  in the dismantling position  130 . The boom tip is let down to the proximity of the ground with an extended boom  30  so that the hoist rope fixing point at the boom tip can be released from the ground. The released hoist rope  50  is secured at the boom  30  including the rope pulleys. The rope reeving pulley  80  is used as a deflection pulley  80  when dismantled. In this respect, the position of the rope reeving pulley  80  at the boom can be varied to be able to provide ideal conditions for the luffing mode. 
     The now free hoist rope fixing point is latched to the available hook  90 . The hoist rope security is subsequently released and the boom  30  is pulled up. 
     In addition, one or more sensors are available at the crane which measure the local geometry at the boom system and which derive the current equipment status using the measured data. The result is communicated to the crane control or to the crane operator. 
     The above-described method steps are carried out in reverse order for the change of the crane configuration from the luffing mode to the trolley mode. 
     A simple possibility of changing the boom configuration during the conversion results by the change of the crane configuration, in particular by the change of the hoist rope reeving. One or more additional elements can be mounted particularly simply and fast at the boom tip for extending the boom  30  during the re-reeving of the hoist rope  40  with a let-down boom  30 . 
       FIG. 3 a    schematically shows the possibility of extending the boom  30 . A boom extension  100  such as a lattice tip can be mounted at the boom tip. Alternatively or additionally, other boom elements can also be introduced into the boom system for providing different functions. There is thus the possibility here of attaching individual elements or apparatus for displaying information to the boom tip. In this connection, reference is in particular made to the attachment of billboards or of electronic display means for the presentation of advertising information. 
     The above-described method for mode changing is made use of for the mounting of a boom extension or of an additional boom element. At least one extension  100  or on additional element, is, however, provided in advance in addition to the crane hook  90 . 
     The method is subsequently carried out up to the securing of the hoist rope  40 . The mounting of the boom extension  100  at the boom tip subsequently takes place. As shown in the detailed view in accordance with  FIG. 3 b   , the hoist rope fixing point is connected for this purpose to a securing rope  110  which extends up to the tip of the boom extension  100 . The securing rope  110  can be wound up onto a hand winch  120  to pull the hoist rope from the boom tip up to the outer end of the boom extension  100 . The rope reeving pulley  80  is dismantled at the boom tip and is fastened to the tip of the boom extension  100 . The hoist rope  40  and the reeving pulley  80  are secured at the new position up to the erection of the boom  30 . The rope reeving pulley  80  mounted at the boom extension takes over the function of a deflection pulley  80  for guiding the hoist rope  40  up to the crane hook  90 . A provided sensor system also recognizes the changed configuration in this case and communicates it to the crane control. 
     The invention now allows a fast change of the crane configuration between the trolley mode and the luffing mode with little equipping effort. The crane in accordance with the invention and the method in accordance with the invention ensure a particularly flexible crane deployment at construction sites with particularly tight space conditions.