Luffing boom tower crane and method for determining positions of first fixed pulley and third fixed pulley

Abstract

The invention discloses a boom-luffing tower crane and a method for determining the positions of a first fixed pulley and a third fixed pulley. The boom-luffing tower crane comprises: a supporting seat; a balancing arm; a lifting arm; a support rod, the bottom of which is connected to the supporting seat through a first connecting point; a pulling rod; a luffing mechanism, comprising a luffing fixed pulley and a luffing rope arranged at the top of the support rod, the luffing rope is unwound from a luffing winch, and is connected to the lifting arm after passing through the luffing fixed pulley, and the luffing mechanism is used to make the lifting arm luffing and rotating relative to the supporting seat; a lifting mechanism, comprising a lifting winch arranged on the balancing arm, a lifting rope, a first fixed pulley arranged at the top of the support rod, a second fixed pulley located at the bottom of the support rod, a third fixed pulley arranged on the support rod and located between the first fixed pulley and the second fixed pulley, and a fourth fixed pulley arranged at the lifting end, when lifting a heavy object, the lifting rope is unwound from the lifting winch, and is connected to the heavy object after passing through the first fixed pulley, the second fixed pulley, the third fixed pulley and the fourth fixed pulley in sequence.

Description

[0001] This application is a divisional application based on the invention with application number 202110722832.4, application date June 28, 2021, applicant Jiangsu Xugong Engineering Machinery Research Institute Co., Ltd., and invention name "Luffing arm type tower crane and method for determining the position of the first fixed pulley and the third fixed pulley". Technical Field

[0002] The invention relates to the field of cranes, in particular to a luffing boom tower crane and a method for determining positions of a first fixed pulley and a third fixed pulley of the luffing boom tower crane. Background Art

[0003] The luffing tower crane is an important lifting machine in the construction industry. The existing luffing tower crane includes a luffing mechanism and a hoisting mechanism. The luffing mechanism changes the luffing arm of the luffing tower crane through the luffing rope, and the hoisting mechanism hoists the heavy objects through the hoisting rope. The working efficiency, stability or working capacity of the luffing tower crane will be affected by the rope winding method of the luffing mechanism and the hoisting mechanism. Summary of the invention

[0004] The object of the present invention is to provide a boom-luffing tower crane with a more reasonable rope winding method of a hoisting mechanism, strong stability and good performance.

[0005] The present invention discloses a boom-luffing tower crane, comprising:

[0006] Support seat;

[0007] A balancing arm, a first end of which is connected to the supporting seat;

[0008] A lifting arm, comprising a connecting end hinged to the support seat and a lifting end for lifting heavy objects;

[0009] A support rod, the bottom of which is connected to the support seat via a first connection point;

[0010] A pull rod, two ends of which are respectively connected to the second end of the balance arm and the top of the support rod;

[0011] A luffing mechanism, comprising a luffing winch provided on the balance arm, a luffing fixed pulley provided on the top of the support rod and a luffing rope, the luffing rope is unwound from the luffing winch, passes through the luffing fixed pulley and is connected to the boom, and the luffing mechanism is used to make the boom rotate relative to the support seat;

[0012] The lifting mechanism includes a lifting winch arranged on the balance arm, a lifting rope, a first fixed pulley arranged on the top of the support rod, a second fixed pulley located at the bottom of the support rod, a third fixed pulley arranged on the support rod and located between the first fixed pulley and the second fixed pulley, and a fourth fixed pulley arranged at the lifting end. When lifting a heavy object, the lifting rope is unwound from the lifting winch, passes through the first fixed pulley, the second fixed pulley, the third fixed pulley and the fourth fixed pulley in sequence, and then is connected to the heavy object.

[0013] In some embodiments, the lifting mechanism also includes a fifth fixed pulley arranged on the balance arm or the support rod, and the fifth fixed pulley is close to the first connection point. The lifting rope is unwound from the lifting hoist, passes through the fifth fixed pulley and then passes through the first fixed pulley.

[0014] In some embodiments, along a direction perpendicular to the luffing plane of the boom, at three positions on both sides and in the middle of the boom, the connection positions of the fourth fixed pulley and the luffing rope with the lifting end are respectively located at different positions among the three positions.

[0015] In some embodiments, the variable amplitude fixed pulley and the first fixed pulley are coaxially arranged.

[0016] In some embodiments, when the lifting winch remains stationary and the boom rotates in a variable amplitude range, the difference between the maximum height and the minimum height of the lifted weight carried by the boom from the ground is the lifting compensation height; when the boom lifts weights at each variable amplitude angle in the entire variable amplitude range at the rated maximum lifting weight of the corresponding angle, the maximum tension of the variable amplitude rope connected to the boom on the boom at each variable amplitude angle is the maximum variable amplitude rope tension; when the boom lifts weights at each variable amplitude angle in the entire variable amplitude range at the rated maximum lifting weight of the corresponding angle, the maximum force of the support seat on the boom at each variable amplitude angle is the maximum boom hinge force; the length between the variable amplitude fixed pulley and the first connection point is the main body length of the support rod; the positions of the first fixed pulley and the third fixed pulley are configured to be determined according to the lifting compensation height, the maximum variable amplitude rope tension, the maximum boom hinge force and the main body length of the support rod.

[0017] In some embodiments, the positions of the first fixed pulley and the second fixed pulley are configured to achieve global optimal determination by optimizing the four optimization objectives of the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge receiving force and the support rod body length.

[0018] In some embodiments, the position of the center of the first fixed pulley belongs to a first area, and the ratio of the distance between the second fixed pulley and the first connection point to the distance between the first fixed pulley and the first connection point belongs to a first value range.

[0019] In some embodiments, when optimizing the four optimization objectives, respective weights of the four optimization objectives are determined according to the sensitivity of each optimization objective to position changes of the first fixed pulley and the third fixed pulley.

[0020] In some embodiments, the sensitivity of each optimization objective is equal to the ratio of the standard deviation of each optimization objective with respect to the function of the position change of the first fixed pulley and the third fixed pulley to the average value.

[0021] In some embodiments, the respective weights of the four optimization objectives are equal to the ratios of the respective sensitivities to the sum of the four sensitivities of the four optimization objectives.

[0022] In some embodiments, the luffing angle range of the boom is (13.4°, 84.5°).

[0023] A second aspect of the present invention discloses a method for determining the positions of the first fixed pulley and the third fixed pulley of the boom-luffing tower crane, wherein the positions of the first fixed pulley and the third fixed pulley are determined according to the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge receiving force and the length of the support rod body.

[0024] Based on the boom-luffing tower crane provided by the present invention, by arranging the first fixed pulley, the second fixed pulley and the third fixed pulley on the support rod, the boom is luffed in the direction of increasing the luffing angle, and within a certain angle range before the luffing angle reaches the maximum, the pulling force of the lifting rope on the support rod relative to the lever arm of the first connection point gradually decreases as the luffing angle increases. When the luffing angle of the boom increases, its lifting capacity is also enhanced, and the maximum weight of the load that can be lifted is also increased. Due to the reduction of the lever arm, the bending moment on the support rod when the maximum weight of the load that can be lifted increases can be reduced, and the pulling force of the pull rod can be reduced, so that the stability of the boom-luffing tower crane is better and the performance is better.

[0025] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 It is a structural schematic diagram of a boom-luffing tower crane according to an embodiment of the present invention;

[0028] Figure 2 for Figure 1 A partial enlarged structural schematic diagram of a part of the structure of a boom-luffing tower crane is shown;

[0029] Figure 3 for Figure 1 The structural schematic diagram of the lifting mechanism of the boom-luffing tower crane is shown. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0032] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0033] A boom-luffing tower crane is a tower crane whose boom can be adjusted by rotation. Figures 1 to 3 As shown, the luffing tower crane of the present embodiment comprises a supporting base 1, a balancing arm 3, a lifting arm 2, a support rod 4, a pulling rod 5, a luffing mechanism and a lifting mechanism.

[0034] In a conventional boom-luffing tower crane, the support base 1 includes a slewing support structure, and structures such as a balance arm 3 and a lifting arm 2 are connected to the slewing support structure. Figure 1 In the illustrated embodiment, the luffing tower crane further comprises a tower body 8 , and the support base 1 is located at the top of the tower body 8 .

[0035] The first end of the balancing arm 3 is connected to the supporting base 1 , and the second end of the balancing arm 3 is provided with a balancing weight 31 .

[0036] The lifting arm 2 includes a connecting end hinged to the supporting base 1 and a lifting end for lifting heavy objects.

[0037] The bottom of the support rod 4 is connected to the support seat 1 through a first connection point 41. The bottom of the support rod 4 can be hinged to the support seat 1, or can be fixedly connected to the support seat 1. The first connection point 41 indicates the connection position between the support rod 4 and the support seat 1, and the actual form is not a point. For example, when the support rod 4 and the support seat 1 are hinged through a hinge axis, the first connection point 41 is the hinge axis.

[0038] The two ends of the pull rod 5 are respectively connected to the second end of the balance arm 3 and the top of the support rod 4;

[0039] The luffing mechanism includes a luffing winch 61 provided on the balance arm 3, a luffing fixed pulley 62 provided on the top of the support rod 4, and a luffing rope 64. The luffing rope 64 is unloaded from the luffing winch 61, passes through the luffing fixed pulley 62, and is connected to the boom 2. The luffing mechanism is used to make the boom 2 rotate relative to the support base 1.

[0040] exist Figure 1 The mid-boom luffing tower crane further includes a cab 10 .

[0041] The lifting mechanism includes a lifting winch 76 arranged on the balance arm 3, a lifting rope 77, a first fixed pulley 71 arranged at the top of the support rod 4, a second fixed pulley 72 located at the bottom of the support rod 4, a third fixed pulley 73 arranged on the support rod 4 and located between the first fixed pulley 71 and the second fixed pulley 72, and a fourth fixed pulley 74 arranged at the lifting end, as well as a hook pulley group 78 arranged at the lifting end. When lifting a heavy object, the lifting rope 77 is unloaded from the lifting winch 76, passes through the first fixed pulley 71, the second fixed pulley 72, the third fixed pulley 73 and the fourth fixed pulley 74 in sequence, and then is connected to the heavy object through the hook pulley group 78.

[0042] The boom luffing tower crane of this embodiment is provided with a first fixed pulley 71, a second fixed pulley 72 and a third fixed pulley 73 on the support rod 4. The luffing angle refers to the angle of the boom relative to the horizontal direction. When the boom 2 rotates counterclockwise, the luffing angle increases, and the lifting capacity of the boom luffing tower crane is enhanced, that is, the rated maximum lifting capacity of the boom 2 increases. In some embodiments, the luffing angle is less than 90 degrees and greater than 0 degrees. Figure 1 In the embodiment, the variable angle of the boom 2 is a degree less than 30 degrees. When the lifting capacity of the boom 2 is changed by changing the variable angle of the boom 2, the boom 2 varies in the direction of increasing the variable angle, and within a certain angle range before the variable angle reaches the maximum, the pulling force of the lifting rope 77 on the support rod 4 gradually decreases relative to the lever arm of the first connection point 41 as the variable angle increases. When the variable angle of the boom 2 increases, its lifting capacity is also enhanced, and the maximum weight of the load that can be lifted is also increased. Due to the reduction of the lever arm, the bending moment on the support rod 4 when the rated maximum lifting weight increases can be reduced, and the pulling force on the tie rod 5 can be reduced, so that the stability of the boom variable tower crane is better and the performance is better. In addition, in this embodiment, the force condition of the rod portion of the support rod 4 located above the second fixed pulley 72 is better than that of the rod portion below the second fixed pulley 72, and the force condition of the rod portion between the second fixed pulley 72 and the first connection point 41 is relatively poor. The second fixed pulley 72 is located at the bottom of the support rod 4, close to the first connection point 41, so as to improve the force condition of most of the rod portions of the support rod 4 as much as possible.

[0043] In some embodiments, Figures 1 to 3As shown, the lifting mechanism further includes a fifth fixed pulley 75 disposed on the balance arm 3 or the support rod 4, and the fifth fixed pulley 75 is close to the first connection point 41. In the embodiment shown in the figure, the fifth fixed pulley 75 is disposed on the balance arm 3. The lifting rope 77 is unloaded from the lifting winch 76, passes through the fifth fixed pulley 75, and then passes through the first fixed pulley 71. The pull rod 5 is used to provide a pulling force to the support rod 4 when the boom luffing tower crane lifts a heavy object. The material and structure of the pull rod 5 are specially designed for tension, and the pull rod 5 should be avoided as much as possible to be compressed. In this embodiment, the fifth fixed pulley 75 is provided, so that the lifting rope 77 between the fifth fixed pulley 75 and the first fixed pulley 71 can be nearly parallel to the support rod 4, so that the bending moment of the lifting rope 77 between the fifth fixed pulley 75 and the first fixed pulley 71 on the support rod 4 in the counterclockwise direction can be reduced as much as possible, thereby avoiding the pressure effect of the lifting rope 77 between the fifth fixed pulley 75 and the first fixed pulley 71 on the pull rod 5.

[0044] In some embodiments, Figures 1 to 3 As shown, along the direction perpendicular to the luffing plane of the boom 2, the fourth fixed pulley 74 and the connection position of the luffing rope 64 with the lifting end are respectively located at different positions in the three positions on both sides and the middle of the boom 2. The luffing plane refers to the plane where the boom 2 is located when the luffing is performed. The boom 2 has a width in the direction perpendicular to the luffing plane. Along the width direction of the boom 2, the connection position of the luffing rope 64 with the lifting end and the position of the fourth fixed pulley 74 are different, so that when the boom 2 increases the luffing angle, the interference between the lifting rope 77 and the luffing rope 64 can be avoided. In the embodiment shown in the figure, the connection position of the luffing fixed pulley 62 and the luffing rope 64 with the lifting end are both located on the left side of the boom 2, the first fixed pulley 71 and the fourth fixed pulley 74 are located on the same side of the connection position of the luffing fixed pulley 62 and the luffing rope 64 with the lifting end, which is the right side in the figure, and the fourth fixed pulley 74 is located in the middle of the boom 2.

[0045] In some embodiments, the variable amplitude fixed pulley 62 and the first fixed pulley 71 are coaxially arranged. In this embodiment, by coaxially arranging the variable amplitude fixed pulley 62 and the first fixed pulley 71, the length of the support rod 4 can be reduced as much as possible, and the weight of the support rod 4 can be reduced. Figure 1 As shown, the positions of the variable amplitude fixed pulley 62 and the first fixed pulley 71 on the support rod 4 can be used as the top end of the support rod 4.

[0046] In some embodiments, when the hoisting winch 76 remains stationary and the boom 2 is variable in amplitude within the entire amplitude range, the difference between the maximum height and the minimum height of the lifted weight carried by the boom 2 from the ground is the lifting compensation height. That is, when the hoisting winch remains stationary, the boom 2 carries the weight and varies from the minimum amplitude angle to the maximum amplitude angle. During this process, the maximum height change of the weight is the lifting compensation height. The smaller the lifting compensation height, the smaller the influence of the amplitude change of the boom 2 on the transportation of the weight, and the smoother the transportation of the weight.

[0047] When the boom 2 lifts heavy objects at each amplitude variation angle within the entire amplitude variation range with the rated maximum lifting capacity of the corresponding angle, the maximum tension of the amplitude variation rope 64 connected to the boom 2 on the boom 2 at each amplitude variation angle is the maximum amplitude variation rope tension. For a boom-luffing tower crane with a certain structure, when the boom 2 is located at a certain amplitude variation angle and lifts heavy objects with the maximum rated lifting capacity, the boom 2 is subjected to a force balance between the gravity of the heavy object, its own gravity, the support force of the support seat 1, the tension of the lifting rope 77 and the tension of the amplitude variation rope 64. A force analysis is performed on the boom 2 to obtain the tension of the amplitude variation rope 64 at a certain amplitude variation angle. When a force analysis is performed on the boom 2 at each amplitude variation angle, the tension of the amplitude variation rope 77 at each amplitude variation angle is obtained, and the maximum amplitude variation rope tension is the largest one. When the amplitude variation mechanism is as follows: Figure 1 When the luffing rod 63 is set as shown, the smaller the maximum luffing pulling force is, the lower the strength and other properties of the luffing rod 63 can be set, the mass of the luffing rod 63 can be reduced, and the force bearing performance of the boom luffing tower crane is also better.

[0048] When the boom 2 lifts heavy objects with the rated maximum lifting capacity of the corresponding angle at each luffing angle within the entire luffing range, the maximum force of the force exerted by the support seat 1 on the boom 2 at each luffing angle is the maximum boom hinge capacity; similar to the analysis of the maximum luffing rope tension, when the force analysis of the boom 2 is carried out at each luffing angle, the supporting force of the support seat 1 on the boom 2 at each luffing angle is obtained, and the largest one is the maximum boom hinge capacity.

[0049] The length between the variable-length fixed pulley 62 and the first connection point 41 is the main body length of the support rod; the smaller the main body length of the support rod is, the lighter the weight of the support rod can be, and the crane can be designed to be lightweight.

[0050] The positions of the first fixed pulley 71 and the third fixed pulley 73 are configured to be determined according to the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge receiving force and the main length of the support rod. In this embodiment, the position of the first fixed pulley 71 is also the position of the luffing fixed pulley 62, and the positions of the first fixed pulley 71 and the third fixed pulley 73 are determined by considering the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge receiving force and the main length of the support rod, so that the boom luffing tower crane can have a more excellent combined performance.

[0051] In some embodiments, the positions of the first fixed pulley 71 and the second fixed pulley 72 are configured to achieve global optimal determination by optimizing the four optimization targets of the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge acceptance force and the support rod body length. Global optimality means that the comprehensive effect of the four optimization targets of the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge acceptance force and the support rod body length is the best, and a single optimization target is not at the optimal value under this optimization method. Global optimality is a kind of combined optimization.

[0052] In some embodiments, the position of the center of the first fixed pulley 71 belongs to the first region, and the first region is a surface domain, that is, a two-dimensional coordinate range, that is, a three-dimensional coordinate system is established with the first connection point 41 as the origin, the horizontal direction along the balance arm 3 as the x-axis, and the vertical direction as the y-axis, and the z-axis coordinate of the first fixed pulley 71 is a constant. The size of the first region is obtained by conventional experience. The x-axis and y-axis coordinates of the first fixed pulley 71 are variables. The ratio of the distance between the third fixed pulley 73 and the first connection point 41 to the distance between the first fixed pulley 71 and the first connection point 41 belongs to the first value range, and the first value range is (0, 1) in some embodiments.

[0053] In some embodiments, when optimizing the four optimization objectives, the respective weights of the four optimization objectives are determined according to the sensitivity of each optimization objective to the position change of the first fixed pulley 71 and the third fixed pulley 73 .

[0054] In some embodiments, the sensitivity of each optimization target is equal to the ratio of the standard deviation of the function of each optimization target with respect to the position change of the first fixed pulley 71 and the third fixed pulley 3 to the average value.

[0055] In some embodiments, the respective weights of the four optimization objectives are equal to the ratio of the respective sensitivities to the sum of the four sensitivities of the four optimization objectives.

[0056] In some embodiments, the luffing angle of the boom 2 ranges from (13.4° to 84.5°).

[0057] In some embodiments, a method for determining the positions of the first fixed pulley 71 and the third fixed pulley 73 of a boom-luffing tower crane is also disclosed. The positions of the first fixed pulley 71 and the third fixed pulley 73 are determined according to the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge bearing force and the length of the support rod body.

[0058] The global optimal optimization method of this embodiment is illustrated below with a specific embodiment. In this embodiment, the coordinate of the first fixed pulley 71 is X, and the ratio of the distance between the third fixed pulley 73 and the first connection point 41 to the distance between the first fixed pulley 71 and the first connection point 41 is l. The single optimization objective is a function of X and l: F i (X, l)(i=1,2,3,4) 。

[0059] First, calculate each optimization objective F i (X, l) (i = 1, 2, 3, 4) the average value AVG of the variable X, l i and standard deviation STDEV i .

[0060] Then calculate the sensitivity YSZ of each optimization target i ,

[0061] Then calculate the weight u of each optimization target i ,

[0062] Finally, we get the combined optimization function

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A boom-luffing tower crane, characterized in that: include: Tower body; A support base (1), located at the top of the tower body, comprising a slewing support structure; A balancing arm (3), a first end of which is connected to the support base (1); A lifting arm (2), comprising a connecting end hinged to the support base (1) and a lifting end for lifting a heavy object; A support rod (4), the bottom of which is connected to the support base (1) via a first connection point (41); A pull rod (5), both ends of which are respectively connected to the second end of the balance arm (3) and the top of the support rod (4); a luffing mechanism, comprising a luffing winch (61) arranged on the balance arm (3), a luffing fixed pulley (62) arranged on the top of the support rod (4), and a luffing rope (64); the luffing rope (64) is unwound from the luffing winch (61), passes through the luffing fixed pulley (62), and is connected to the boom (2); the luffing mechanism is used to cause the boom (2) to rotate relative to the support seat (1); A lifting mechanism, comprising a lifting winch (76) arranged on the balance arm (3), a lifting rope, a first fixed pulley (71) arranged on the top of the support rod (4), a second fixed pulley (72) located at the bottom of the support rod (4), a third fixed pulley (73) arranged on the support rod (4) and located between the first fixed pulley (71) and the second fixed pulley (72), and a fourth fixed pulley (74) arranged at the lifting end. When lifting a heavy object, the lifting rope is unloaded from the lifting winch (76), passes through the first fixed pulley (71), the second fixed pulley (72), the third fixed pulley (73) and the fourth fixed pulley (74) in sequence, and is connected to the heavy object. The variable-length fixed pulley (62) and the first fixed pulley (71) are coaxially arranged, and when the hoisting winch (76) remains stationary and the boom (2) is variable-length and rotated within the entire variable-length range, the difference between the maximum height and the minimum height of the lifted weight carried by the boom (2) from the ground is the lifting compensation height; when the boom (2) lifts weights at each variable-length angle within the entire variable-length range at the rated maximum lifting weight of the corresponding angle, the maximum tension of the variable-length rope (64) connected to the boom (2) on the boom (2) at each variable-length angle is the maximum variable-length rope tension; when the boom (2) lifts weights at each variable-length angle within the entire variable-length range at the rated maximum lifting weight of the corresponding angle, the maximum force of the force applied by the support seat (1) on the boom (2) at each variable-length angle is the maximum boom hinge stress; The length between the luffing fixed pulley (62) and the first connection point (41) is the main body length of the support rod; the positions of the first fixed pulley (71) and the third fixed pulley (73) are configured to be determined according to the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge receiving force and the main body length of the support rod.

2. The boom-luffing tower crane according to claim 1, characterized in that: The lifting mechanism further comprises a fifth fixed pulley (75) arranged on the balance arm (3) or the support rod (4), the fifth fixed pulley (75) being close to the first connection point (41), and the lifting rope is unloaded from the lifting winch (76), passes through the fifth fixed pulley (75) and then passes through the first fixed pulley (71).

3. The boom-luffing tower crane according to claim 1, characterized in that: Along a direction perpendicular to the luffing plane of the boom (2), at three positions on both sides and in the middle of the boom (2), the connection positions of the fourth fixed pulley (74) and the luffing rope (64) with the lifting end are respectively located at different positions among the three positions.

4. The luffing tower crane according to claim 1, characterized in that: The positions of the first fixed pulley (71) and the second fixed pulley (72) are configured to achieve global optimal determination by optimizing four optimization objectives: the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge receiving force and the support rod body length.

5. The luffing tower crane according to claim 4, characterized in that: The position of the center of the first fixed pulley (71) belongs to the first area, and the ratio of the distance between the third fixed pulley (73) and the first connection point (41) to the distance between the first fixed pulley (71) and the first connection point (41) belongs to the first value range.

6. The luffing tower crane according to claim 4, characterized in that: When optimizing the four optimization objectives, the respective weights of the four optimization objectives are determined according to the sensitivity of each optimization objective to the position change of the first fixed pulley (71) and the third fixed pulley (73).

7. The luffing tower crane according to claim 6, characterized in that: The sensitivity of each optimization target is equal to the ratio of the standard deviation of each optimization target with respect to the function of the position change of the first fixed pulley (71) and the third fixed pulley (73) to the average value.

8. The luffing tower crane according to claim 6, characterized in that: The respective weights of the four optimization objectives are equal to the ratios of the respective sensitivities to the sum of the four sensitivities of the four optimization objectives.

9. The luffing tower crane according to any one of claims 1 to 8, characterized in that: The range of the variable angle of the boom (2) is (13.4°, 84.5°).

10. A method for determining the positions of the first fixed pulley (71) and the third fixed pulley (73) of the luffing tower crane according to any one of claims 1 to 8, characterized in that: The positions of the first fixed pulley (71) and the third fixed pulley (73) are determined according to the lifting compensation height, the maximum luffing rope tension, the maximum boom hinge receiving force and the length of the support rod body.

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