Abstract:
A telescopic crane, includes a substructure, a superstructure rotatably mounted onto the substructure, a counterweight and a telescoping boom structure which includes a main boom slewable about a luffing plane. The main boom has a boom base and at least one telescope section received in the boom base and displaceable between retracted and extended positions. At least one guy support is mounted to the boom structure and connected to a guy rope which extends substantially longitudinally in the direction of the boom structure. The guy support is oriented with respect to the luffing plane at an inclination which is so selected that a lateral load acting on the boom structure is partially or entirely received by the guying.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the priority of German Patent Application, Ser. No. 199 305 37.4, filed Jun. 28, 1999, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a telescopic crane of a type having a substructure, a revolving superstructure mounted to the substructure, a counterweight and a boom structure comprised of a main boom having a boom base and at least one telescope section which is received in the boom base and displaceable between retracted and extended positions. 
     In extended position, telescopic cranes are exposed to varying degrees of stress depending on the angular disposition. Oftentimes, the lateral deformation of the main boom in steep-incline disposition is the criterion that limits the load-carrying capability. When the angular disposition is flat or average, the loads applied in the mounting of the extended telescope sections represent a crucial criterion for the maximum load-carrying capability. In the latter case, the so-called super lift operation has been developed for torque relief. 
     The use of telescopic cranes with super lift operation has been known for a long time. An example is illustrated in a brochure issued by Mannesmann Demag Fordertechnik, Demag AX 1600, April 1996, pages 5, 17 and 27. A guy truss is arranged on the boom base of the main boom for placement on the boom base to increase the load-carrying capability and to reduce sag of the main boom. The guy truss is connected, on the one hand, to the foot region of the main boom via a guy rope of substantially constant length, and, on the other hand, to the head or collar of one of the inner telescope sections via a further guy rope of normally variable length. This reinforcing configuration is applicable for the base unit alone, or in conjunction with the arrangement of a fly jib in the form of a latticed tower which can be of the fixed type or luffing type. Telescopic cranes of this kind suffer shortcomings because the boom structure deforms laterally, especially in steep-incline disposition. 
     SUMMARY OF THE INVENTION 
     It is thus an object of the present invention to provide an improved telescopic crane, obviating the afore-stated drawbacks. 
     In particular, it is an object of the present invention to provide an improved telescopic crane whose lateral deformation of the boom structure is significantly reduced, in particular in steep-incline disposition, compared to conventional telescopic cranes. 
     These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing at least one guy support which is mounted to the boom structure and connected to a tension means extending substantially longitudinally in the direction of the boom structure, with the guy support oriented with respect to the luffing plane at an inclination which is so selected that a lateral load acting on the boom structure is partially or entirely received by the guying. 
     The inclination of the guy support can be realized transversely to the longitudinal direction or in longitudinal direction or in superimposed transversely to and longitudinally in direction of the boom structure. 
     According to another feature of the present invention, two inclined guy supports can be provided on the topside of the respective boom element of the boom structure, whereby the angular disposition of both guy supports is normally identical. Of course, the angular disposition of both guy supports may also differ depending on the direction of the forces acting on the boom structure. The foot ends of both guy supports may be connected to the topside of the boom structure at a common area, or may be offset to one another. It is also conceivable to connect the foot end of at least one of the guy supports with the boom structure in the transition zone between topside and respective sidewall. As an alternative, there is also the option to arrange the foot end of at least one of the guy supports upon a girder which extends transversely to the longitudinal axis of the boom structure and projects beyond the boom structure. 
     Through the provision of a guy support according to the present invention, the portion of the guying force, effective in lateral direction, can be gradually and continuously modified in dependence on the angular disposition of the guy support. In the event, two guy supports are arranged offset to one another, both parallel guy supports act as super lift operation in a same manner as the conventional guy truss, when the boom structure is in the one extreme disposition, i.e. vertical disposition. At an angular position of &lt;90° to &gt;0° for both guy supports, the effective tautening force is split into a component super lift operation and a component lateral guying. In the other extreme position, i.e. horizontal disposition, both guy supports realize a reinforcement in both lateral directions. 
     The free head end of each guy support can be selectively connected via a first tension member with the substructure, the superstructure, the foot region of the boom structure, the fixed or separately guided counterweight, or the bottom in the direction of the boom structure, and via a further tension member with a selected area of the boom structure in the direction of its head. The respectively desired angular disposition of the guy supports may be adjusted step-by-step or continuously by swinging the guy supports, so that an asymmetric angular disposition is also possible. Thus, when a lateral force is applied on one side, the respective guy support is inclined progressively in the direction of lateral guying whereas the other guy support remains in a central disposition. 
     As the distance of the tension members from the boom structure has also an impact on the desired reinforcement, it is proposed to change the length of the guy supports in steps or continuously. The tension members may be a guy rope or a guy rod, and may be arranged with or without prestress. When prestressed at a degree that can be re-adjusted, the tension means is operatively connected with a tensioning mechanism. Suitably, the tensioning mechanism is a winch or a piston and cylinder unit. However, it is also possible, to exploit the angular disposition and/or change in length of the guy supports as tensioning mechanism. The tensioning mechanism may be selectively mounted to the guy supports, to the boom structure, to the superstructure or substructure, or to the counterweight. 
     According to another feature of the present invention, the guy supports are mounted to the main boom in the area of the boom base, in particular in the forward region between the hinged attachment of the luffing cylinder and the forward bearing on the boom base. Each guy support is suitably connected to a piston and cylinder unit which is mounted to the boom base, for continuous adjustment of the guy supports. 
     According to another feature of the present invention, the guy support includes two poles between which the winch may be positioned. 
     A telescopic crane according to the present invention may be further complemented by a fixed or luffing fly jib in the form of a latticed mast. Guy supports in accordance of the present invention may also be mounted to this type of jib. 
     A lateral guying is especially effective when the crane is provided with a measuring device, e.g. a load cell, for detecting a lateral deformation of the boom structure. When the deformation exceeds a predetermined admissible value, the tension member connected to the guying is activated for tautening the guying. The extent of lateral deformation can be registered directly or indirectly via crane parameters, for example, the rope tension, the rope length and the rope extension. However, forces acting upon the boom structure may be used for determination the degree of lateral deformation, such as side winds, exposure to sunlight and temperature of the boom structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects, features and advantages of the present invention will be more readily apparent upon reading the following description of preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
     FIG. 1 a  is a principal illustration of a first embodiment of a telescopic crane according to the present invention, illustrating the arrangement of a guy support which is inclined with respect to the luffing plane; 
     FIG. 1 b  is a 90° rotated disposition thereof; 
     FIG. 1 c  is a perspective illustration thereof; 
     FIG. 2 is a principal illustration of a second embodiment of a telescopic crane according to the present invention, illustrating the arrangement of two inclined guy supports converging at a common foot end; 
     FIGS. 3 a  to  3   d  are principal illustrations of a third embodiment of a telescopic crane according to the present invention, illustrating variations of an arrangement of two inclined guy supports terminating in separate foot ends; 
     FIG. 4 is a principal illustration of a fourth embodiment of a telescopic crane according to the present invention, illustrating the arrangement of a guy support in traverse disposition: 
     FIG. 5 a  is a front view of an exemplified telescopic crane embodying the principles of the present invention with two inclined guy supports, 
     FIG. 5 b  is a side view thereof, 
     FIG. 6 is a block diagram of a measuring circuit for detecting a lateral deformation of the boom structure of a telescopic crane according to the present invention; and 
     FIGS. 7 a - 7   c  show various exemplified illustrations of telescopic cranes embodying the principles of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. 
     Turning now to the drawing, and in particular to FIG. 1 a , there is shown a principal illustration of a first embodiment of a telescopic crane according to the present invention, illustrating the arrangement of a mast-like guy support  2  which is inclined with respect to the luffing plane. The guy support  2  is mounted, preferably, onto the topside of an exemplified boom element  1  of a boom structure (not shown). The boom element  1  is shown here only symbolically by way of a box for sake of simplicity and may represent a boom base or a telescope section of a main boom of the telescopic crane or the latticed tower of a fixed or luffing fly jib. The boom element  1  is defined by a center axis  4  which, ideally, is also the luffing plane of the boom structure. 
     In accordance with the present invention, the guy support  2  is inclined with respect to the luffing plane at an angle of α&gt;0. As shown by broken lines, the guy support  2  may also be inclined to the other side. The guy support  2  has a free end  5  which is guyed by means of tension members  6 ,  7 , preferably guy ropes. Although not shown in detail, the tension members  6 ,  7  are connected at a fixed point on the boom structure, or a tensioning mechanism such as a piston and cylinder unit, or a winch. Tautening of the tension members  6 ,  7  may, however, also be realized without use of a tensioning mechanism by arranging the tension members  6 ,  7  at a smaller or greater angle α and then further inclining the guy support  2 . As an alternative, it is also possible to make the guy support  2  of telescopic configuration to effectuate a tautening through change in length. 
     As shown in FIG. 1 b , which is an illustration in 90° rotated disposition, the guy support  2  may also be inclined in another plane at an angle β&gt;0. FIG. 1 c  shows the option to superimpose the inclination of the guy support  2  in both planes. 
     Turning now to FIG. 2, there is shown a principal illustration of a second embodiment of a telescopic crane according to the present invention, illustrating the arrangement of two inclined guy supports  2 . 1 ,  2 . 2  which converge to a single common foot end  8  swivel-hinged at the topside  3  of the boom element  1 . The angle of inclination α1 of the guy support  2 . 1  with respect to the luffing plane  4  and the angle of inclination α2 of the guy support  2 . 2  with respect to the luffing plane  4  may be identical or different. 
     FIGS. 3 a  to  3   d  show principal illustrations of a third embodiment of a telescopic crane according to the present invention, illustrating variations of an arrangement of two inclined guy supports  2 . 1 ,  2 . 2  terminating in separate foot ends  8 . 1 ,  8 . 2 , respectively. In FIG. 3 a , the foot ends  8 . 1 ,  8 . 2  terminate on the topside  3  of the boom element  1  whereas in FIG. 3 b  the foot ends  8 . 1 ,  8 . 2  terminate in the transition zone from the topside  3  to the respective sidewall  9 . FIG. 3 c  depicts the option to arrange at least one of the foot ends, here foot end  8 . 1 , outside of the boom element  1 . In this case, a girder  10  is secured onto the topside  3  and projects out to the right of FIG. 3 c , with the foot end  8 . 1  of the guy support  2 . 1  swivel-hinged to the end of the girder  10 . FIG. 3 d  shows the option to place onto the topside  3  of the boom element  1  a girder  11  which projects out from both sides of the boom element  1  so that both foot ends  8 . 1 ,  8 . 2  of both guy supports  2 . 1 ,  2 . 2  are positioned outside the boom element  1 . 
     A special case is illustrated in FIG. 4 which depicts the provision of a guy support in the form of a girder  12  extending across the topside  3  of the boom element  1  beyond the boom element  1 . This special case can be realized by positioning the guy supports  2 . 1 ,  2 . 2  of FIG. 2 at angles of inclinations α1 and α2 of 90°. 
     Referring now to FIGS. 5 a  and  5   b , there are shown a front view and a side view, respectively, of an exemplified telescopic crane embodying the principles of the present invention with two inclined guy supports  2 . 1 ,  2 . 2 . In this non-limiting example, the boom element  1  is represented by a boom base of a main boom of the telescopic crane. Swingably mounted to the topside  3  of the boom base  1  is a superstructure  15  which is connected to the boom base  1  via brackets  16 . The superstructure  15  includes an upper girder  19  and a lower girder  17  which has opposite ends for respective attachment of the guy supports  2 . 1 ,  2 . 2  which are tiltable to the side. The guy support  2 . 1  is tilted continuously by a piston and cylinder unit  20 . 1  which has one end hinged to the guy support  2 . 1  and another end hinged to the upper girder  19  of the superstructure  3 . Likewise, the guy support  2 . 2  is tilted continuously by a piston and cylinder unit  20 . 2  which has one end hinged to the guy support  2 . 2  and another end hinged to the upper girder  19  of the superstructure  15 . The example shown in FIGS. 5 a ,  5   b  illustrates the case in which the right-hand guy support  2 . 1  is in a vertical disposition, comparably to a guy truss, while the left-hand guy support  2 . 2  occupies the greatest slewable disposition. 
     As the guy supports  2 . 1 ,  2 . 2  are of an identical construction, the following description refers only to the guy support  2 . 1 . However, it will be understood by persons skilled in the art that a description of one of the guy supports  2 . 1 ,  2 . 2  is equally applicable to the other one of the guy supports  2 . 1 ,  2 . 2 . The guy support  2 . 1  includes two poles  13  which extend substantially parallel in the lower section and slightly converge in the area of the upper section. Interconnection of both poles  13  is realized by crossbars  14 . The inner one of the poles  18  is provided at its foot end with a hinge  24 . The outer one of the poles  13  bears upon the upper portion of the sidewall  9  of the boom base  1  when the guy supports  2 . 1  occupies their greatest inclination. This respective point of attack on the sidewall  9  is suitable reinforced by sheet metal  26 . A winch  27  is rigidly positioned between the poles  13  in the lower area of the guy support  2 . 1 . A guy rope  29  is secured on one end via a rope-end fitting or thimble  31  to the top region of the guy support  2 . 1  and is guided from there in the direction to a point of reversal (not shown), arranged at the boom tip, and back to a deflector sheave  30  disposed in the top area of the guy support  2 . 1 . Form there, the guy rope  29  runs to the winch  27 . Positioned on the backside in the top area of the guy support  2 . 1  is a guy rod  32  for providing a rear safety mechanism for the guy support  2 . 1 . 
     As described above, the superstructure  15  is swingable so that both guy supports  2 . 1 ,  2 . 2  can be deposited parallel to the topside  3  of the base boom  1  for transport of the telescopic crane. To raise again the guy supports  2 . 1 ,  2 . 2 , each of the guy supports  2 . 1 ,  2 . 2  is provided as set-up aid with a piston and cylinder unit  28  (only the piston and cylinder unit  28  of guy support  2 . 1  is shown here) which has one end hinged to the sidewall  25  and another end hinged to a central region of the pertaining guy support. 
     As shown in FIG. 6 the lateral guying is especially effective when providing the crane with a measuring device for detecting a lateral deformation of the boom structure. When the deformation exceeds a predetermined admissible value, the tension member connected to the guying is activated for tautening the guying. The extent of lateral deformation can be registered directly or indirectly by the measuring device via crane parameters, for example, the rope tension, the rope length and the rope extension. However, forces acting upon the boom structure may be used for determination the degree of lateral deformation, such as side winds, exposure to sunlight and temperature of the boom structure. 
     FIGS. 7 a - 7   c  show various exemplified illustrations of telescopic cranes embodying the principles of the present invention. FIG. 7 a  shows a schematic illustration of a mobile telescopic boom crane, generally designated by reference numeral  40  and including a boom base  41  and a plurality of telescope sections  42 , with the laterally inclined guy supports  2 . 1 ,  2 . 2  arranged in a forward region between a luffing cylinder  43  and a forward bearing  44  on the boom base  41 . The guy supports  2 . 1 ,  2 . 2  have free ends  45  which are connected by boom guy lines  46  in the direction of the boom structure head  47  with the head section or collar  48  of an inner one of the telescope sections  42 . 
     FIG. 7 b  shows a schematic illustration of the telescopic boom crane  40  provided with a rigid fly jib, generally designated by reference numeral  49  to form a tower-like latticed extension of the boom crane  40 . The fly jib  49  is mounted to the head  48  of the innermost one of the telescope sections  42 . 
     FIG. 7 c  shows a schematic illustration of a telescopic boom crane, generally designated by reference numeral  50  and including a plurality of telescope sections  52  and a mast  51 . The boom crane  50  is extended by a luffing fly jib, generally designated by reference numeral  52  to form a tower-like latticed extension of the boom crane  50 . The luffing jib  52  has at least one, suitably two, slewed supports  53  which are mounted to the head  54  of an innermost one of the telescope sections  52 . 
     While the invention has been illustrated and described as embodied in a telescopic crane, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.