Luffing pulley frame slot adjustment device and boom assembly, crane

Abstract

The present invention relates to the technical field of engineering machinery, and provides a slot adjustment device for a luffing pulley frame, a boom assembly, and a crane, comprising a guide plate and an adjustment mechanism, wherein the guide plate is used to guide the luffing pulley frame into the slot, and the first end of the guide plate is rotatably connected to the boom; the adjustment mechanism is arranged on the boom, and the adjustment mechanism is connected to the guide plate, and the adjustment mechanism can drive the guide plate to swing in a direction close to or away from the boom. The state of the guide plate can be automatically adjusted as needed by the adjustment mechanism, which greatly saves labor costs and time costs, and can also avoid the risk of the wire rope being de-slotted from the luffing pulley frame due to improper operation or the guide plate squeezing the wire rope, and avoid the risk of the pulley of the luffing pulley frame being damaged due to excessive lateral squeezing force of the wire rope.

Description

Technical Field

[0001] The invention relates to the technical field of engineering machinery, and in particular to a slot adjustment device for a variable-length pulley frame, a boom assembly and a crane. Background Art

[0002] The main luffing wire rope of the truss crawler crane is slowly released during the boom-lowering process. Figure 1 As shown in the figure, the roller of the luffing pulley frame falls on the guide plate. At this time, the guide plate needs to be tilted up at a certain angle. Under the action of gravity, the luffing pulley frame slides along the guide plate to the ear plate of the boom, as shown in the figure. Figure 2 As shown in the figure; when the crane is transported with the boom, the luffing pulley frame and the boom ear plate are fixed with pins, and then the guide plate is laid flat. At present, the position of the guide plate is adjusted manually, which is time-consuming and labor-intensive. Moreover, when the wire rope is at a low position, the wire rope is in a tightened state. Due to the large tilt angle of the guide plate, the guide plate squeezes the wire rope, causing the wire rope to be out of the groove, and the pulley of the luffing pulley frame is subjected to excessive lateral squeezing force from the wire rope. Figure 3 As shown, there is a risk of pulley damage. Summary of the invention

[0003] The present invention provides a slot adjustment device for a variable-length pulley frame, a boom assembly and a crane, so as to solve the defects in the prior art that the position of a guide plate is adjusted manually, which is time-consuming and labor-intensive, and there is a risk of a wire rope slipping out of the slot and a pulley being damaged due to an excessively large tilting angle of the guide plate.

[0004] The present invention provides a slot adjustment device for a luffing pulley frame, comprising:

[0005] A guide plate, used for guiding the luffing pulley frame into the groove, wherein the first end of the guide plate is rotatably connected to the arm frame;

[0006] The adjusting mechanism is arranged on the arm and connected to the guide plate. The adjusting mechanism can drive the guide plate to swing in a direction close to or away from the arm.

[0007] According to the present invention, a slot adjustment device for a luffing pulley frame further comprises a slot detection device, which is used to detect whether the luffing pulley frame is in place, and the slot detection device is connected to the adjustment mechanism for communication, wherein:

[0008] When the slot-entry detection device detects that the luffing pulley frame is in place in the slot, the adjustment mechanism drives the guide plate to rotate in a direction close to the boom.

[0009] According to a slot adjustment device for a luffing pulley frame provided by the present invention, the slot detection device comprises a detection element for detecting the roller position of the luffing pulley frame, and the detection element is arranged on the guide plate.

[0010] According to a slot adjustment device for a variable-length pulley frame provided by the present invention, the detection element is arranged at the intersection of the arc and the guide surface of the guide plate or below the intersection, wherein the arc is a line constructed with the center of the pin hole of the ear plate of the arm frame as the center and the distance between the center of the roller and the center of the pin hole of the variable-length pulley frame as the radius.

[0011] According to the present invention, a luffing pulley frame slot adjustment device further includes a boom angle detection device, the boom angle detection device is used to detect the angle between the boom and the horizontal plane, and the boom angle detection device is communicatively connected with the adjustment mechanism, wherein:

[0012] When the boom angle detection device detects that the angle between the boom and the horizontal plane is greater than a preset angle, the adjustment mechanism drives the guide plate to rotate to an initial position, where the initial position is a position where the guide plate can guide the variable amplitude pulley frame into a groove.

[0013] According to a device for adjusting the entry of a variable-length pulley frame into a slot provided by the present invention, the adjusting mechanism comprises a telescopic device, one end of the telescopic device is used for rotational connection with the boom, and the other end of the telescopic device is rotationally connected with the guide plate.

[0014] According to the slot adjustment device for a variable-length pulley frame provided by the present invention, two guide plates and two adjustment mechanisms are provided, and the guide plates and the adjustment mechanisms are respectively arranged on two opposite sides of the arm frame.

[0015] According to the slot adjustment device for a variable-length pulley frame provided by the present invention, the telescopic device is an adjusting oil cylinder or an air cylinder or an electric push rod or a compression spring.

[0016] The present invention also provides a boom assembly, comprising a boom, a luffing pulley frame and a slot adjustment device for the luffing pulley frame as described in any one of the above items.

[0017] The present invention further provides a crane, comprising the boom assembly as described above or the slot adjustment device for the variable-length pulley frame as described in any one of the above.

[0018] The device for adjusting the entry of a luffing pulley frame into a slot, the boom assembly, and the crane provided by the present invention can automatically adjust the state of the guide plate as needed through the adjustment mechanism, which greatly saves labor costs and time costs, and can also avoid the risk of the wire rope falling out of the slot of the luffing pulley frame due to improper operation or the guide plate squeezing the wire rope, and avoid the risk of the pulley of the luffing pulley frame being damaged due to excessive lateral squeezing force of the wire rope. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a structural schematic diagram of a crane in the prior art (when the luffing pulley frame is in the groove);

[0021] Figure 2 yes Figure 1 One of the enlarged views of the first state at A in the middle;

[0022] Figure 3 yes Figure 1 The second enlarged view of the second state at A (schematic diagram of the wire rope extrusion pulley);

[0023] Figure 4 It is a structural schematic diagram of the crane provided by the present invention;

[0024] Figure 5 This is a schematic diagram of the variable-length pulley frame provided by the present invention entering the groove Figure 1 (The guide plate is in an upward state);

[0025] Figure 6 This is a schematic diagram of the variable-length pulley frame provided by the present invention entering the groove Figure 2 (The guide plate is in an upward state);

[0026] Figure 7 is a schematic diagram of the guide plate provided by the present invention being in a flat state;

[0027] Figure 8 It is a position relationship diagram of the boom and the boom angle detection device provided by the present invention;

[0028] Fig. 9 It is a structural schematic diagram of the crane mainframe provided by the present invention.

[0029] Reference numerals:

[0030] 1: Boom; 2: Boom pulley frame; 3: Wire rope; 4: Guide plate; 5: Adjustment cylinder; 6: Detection element; 7: First data transmission line; 8: Angle sensor; 9: Second data transmission line; 10: Controller; 11: Main data transmission line; 12: Arc; 13: Ear plate pin hole; 21: Roller. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0032] Combine the following Figures 4 to 9 The invention describes a luffing pulley frame slot adjustment device, a boom assembly and a crane.

[0033] like Figure 4-5 As shown, a device for adjusting the entry of a variable-length pulley frame into a slot provided by the present invention comprises a guide plate 4 and an adjusting mechanism.

[0034] Among them, the guide plate 4 is used to guide the luffing pulley frame 2 into the groove, so that the luffing pulley frame 2 can slide along the guide plate 4 to the ear plate of the boom 1 under the action of gravity, and can make the luffing pulley frame 2 lie flat on the ear plate of the boom 1, so that the luffing pulley frame 2 can enter the groove smoothly, meeting the requirements of the main machine when transporting the boom 1.

[0035] Furthermore, the first end of the guide plate 4 is rotatably connected to the arm frame 1 , so that when the luffing pulley frame 2 enters the groove, the guide plate 4 can be rotated to move away from the luffing pulley frame 2 .

[0036] The adjusting mechanism can be arranged on the boom 1, and the adjusting mechanism is connected to the guide plate 4, and the adjusting mechanism can drive the guide plate 4 to swing in the direction close to or away from the boom 1, that is, the adjusting mechanism can drive the guide plate 4 to swing in the direction close to or away from the luffing pulley frame 2, so that the guide plate 4 is close to or away from the luffing pulley frame 2. The adjusting mechanism can make the guide plate 4 away from the luffing pulley frame 2, so as to avoid the guide plate 4 squeezing the wire rope 3 to cause the wire rope 3 to be out of the groove and to avoid the pulley of the luffing pulley frame 2 being subjected to excessive lateral squeezing force of the wire rope 3 to cause damage to the pulley.

[0037] It should be noted that when the guide plate 4 is in the state of guiding the supporting variable-length pulley frame 2, at this time, the guide plate 4 is in the initial position, that is, the guide plate 4 is in the upturned state, and the angle between the guide plate 4 and the arm frame 1 is the initial angle. When the adjustment mechanism drives the guide plate 4 to swing to the second position, the guide plate 4 is in a flat state. In addition, the first end of the guide plate 4 can be the connecting end of the guide plate 4 (that is, the bottom end of the guide plate 4 when it is in the upturned state), and the second end of the guide plate 4 can be the movable end of the guide plate 4 (that is, the top end of the guide plate 4 when it is in the upturned state).

[0038] With such arrangement, the state of the guide plate 4 can be automatically adjusted as needed through the adjustment mechanism, which greatly saves labor costs and time costs, and can also avoid the risk of the wire rope 3 being derailed from the variable-length pulley frame 2 due to improper operation or the guide plate 4 squeezing the wire rope 3, and avoid the risk of the pulley of the variable-length pulley frame 2 being damaged due to excessive lateral squeezing force from the wire rope 3.

[0039] In an optional embodiment of the present invention, the slot adjustment device for the variable-length pulley frame also includes a slot detection device, which is used to detect whether the variable-length pulley frame 2 is in the slot, and the slot detection device is communicatively connected with the adjustment mechanism, so that the slot detection device can transmit the detected signal to the adjustment mechanism, so that the adjustment mechanism can adjust the state (position) of the guide plate 4.

[0040] When the slot detection device detects that the luffing pulley frame 2 is in place, the adjustment mechanism drives the guide plate 4 to rotate in the direction close to the boom 1, so that the guide plate 4 is away from the luffing pulley frame 2. Specifically, the adjustment mechanism drives the guide plate 4 to rotate to the second position, so that the guide plate 4 is in a flat state, such as Figure 5 Like this, guide plate 4 can not squeeze steel wire rope 3, thus can not cause steel wire rope 3 to be out of groove and pulley to be damaged.

[0041] In an optional embodiment, the slot detection device includes a detection element 6, which is disposed on the guide plate 4 and is used to detect the position of the roller 21 of the luffing pulley frame 2, thereby detecting whether the luffing pulley frame 2 is slotted.

[0042] Here, when the detection element 6 detects the roller 21, it means that the luffing pulley frame 2 is in the groove.

[0043] In this embodiment, the detection element 6 can be arranged at the intersection of the arc 12 and the guide surface of the guide plate 4 or below the intersection, wherein Figure 6 As shown, the arc 12 may be a line constructed with the center of the ear plate pin hole 13 of the boom 1 as the center and the distance between the center of the roller 21 and the center of the pin hole of the luffing pulley frame 2 as the radius. That is, the detection element 6 may be arranged at the position where the roller 21 contacts the guide plate 4 or below the contact position when the luffing pulley frame 2 is in place.

[0044] It should be noted that when the luffing pulley frame 2 is inserted into the groove, the pin hole of the luffing pulley frame 2 is coaxially connected with the ear plate pin hole 13 of the boom 1.

[0045] In one mode of this embodiment, the detection element 6 can be a contact switch or a travel switch, and the contact switch or the travel switch can be set at the intersection of the arc 12 and the guide surface of the guide plate 4. In this way, when the contact switch detects the roller 21, it means that the variable amplitude pulley frame 2 is in the groove.

[0046] In another embodiment of the present invention, the detection element 6 may be a distance detection switch or a distance detection sensor, for example, the detection element 6 may be a proximity switch or a distance sensor. Here, the distance detection switch or the distance detection sensor may be arranged below the intersection of the arc 12 and the guide surface of the guide plate 4, so that when the distance detection switch or the distance detection sensor is on, it indicates that the luffing pulley frame 2 is in place.

[0047] It should be noted that the specific position of the distance detection switch or the distance detection sensor can be determined according to the distance measurement range of the selected distance detection switch or the distance detection sensor, and the specific position of the distance detection switch or the distance detection sensor is not limited here.

[0048] In this embodiment, if Figure 5-Figure 7 As shown, the slot entry detection device also includes a first data transmission line 7, which is electrically connected to the detection element 6, and the first data transmission line 7 can be communicatively connected to the adjustment mechanism to facilitate the detection signal of the detection element 6 to be transmitted to the adjustment mechanism, thereby facilitating the adjustment mechanism to regulate the guide plate 4.

[0049] In an optional embodiment of the present invention, the device for adjusting the luffing pulley frame into the slot further includes a boom angle detection device, and the boom angle detection device is used to detect the angle between the boom 1 and the horizontal plane.

[0050] In addition, the boom angle detection device is communicatively connected with the adjustment mechanism, so that the boom angle detection device can transmit the detected angle information between the boom 1 and the horizontal plane to the adjustment mechanism, so that during the boom raising process, the adjustment mechanism adjusts the angle of the guide plate 4 according to the received information, thereby preventing the guide plate 4 from squeezing the wire rope 3 during the return process and causing the wire rope 3 to be out of the groove or causing the pulley to wear.

[0051] When the arm angle detection device detects that the angle between the arm 1 and the horizontal plane is greater than the preset angle, the adjustment mechanism drives the guide plate 4 to rotate to the initial position, so that the guide plate 4 can play a guiding and supporting role for the next entry of the luffing pulley frame 2 into the groove. Here, the initial position of the guide plate 4 is the position when the guide plate 4 can guide the luffing pulley frame 2 into the groove, that is, the position when the guide plate 4 contacts the roller 21 of the luffing pulley frame 2.

[0052] It should be noted that the preset angle can be: during the arm-raising process, when the luffing pulley frame 2 is in place, the angle value of the angle between the arm frame 1 and the horizontal plane detected by the arm frame angle detection device. Since the roller 21 of the luffing pulley frame 2 is in contact with the guide plate 4 when the luffing pulley frame 2 is in place during the arm-raising process; and in order to avoid the guide plate 4 from squeezing the wire rope 3 or the luffing pulley frame 2 during the arm-raising process, when the angle between the arm frame 1 and the horizontal plane is greater than the preset angle, the adjustment mechanism drives the guide plate 4 to rotate to the initial position, at which time the guide plate 4 will not contact the luffing pulley frame 2 and the wire rope 3, thereby preventing the wire rope 3 from slipping out of the groove or the pulley from being damaged.

[0053] In this embodiment, Figure 8 As shown, the boom angle detection device includes an angle sensor 8 and a second data transmission line 9, the angle sensor 8 is arranged on the boom 1, the angle sensor 8 is used to detect the angle between the boom 1 and the horizontal plane, the second data transmission line 9 is electrically connected to the angle sensor 8, and the second data transmission line 9 is used to communicate with the adjustment mechanism, so as to transmit the signal detected by the angle sensor 8 to the adjustment mechanism, thereby facilitating the adjustment mechanism to regulate the guide plate 4.

[0054] In an optional embodiment, if Fig. 9 As shown, the slot adjustment device for the luffing pulley frame also includes a data processing system, which is installed on the crane host, and includes a controller 10 and a main data transmission line 11, the main data transmission line 11 is electrically connected to the controller 10, the main data transmission line 11 is electrically connected to the first data transmission line 7 and the second data transmission line 9, and the controller 10 is in communication connection with the adjustment mechanism. In this way, it is convenient for the slot detection device and the boom angle detection device to transmit the detected signals to the controller 10, and the controller 10 regulates the adjustment mechanism according to the signals, thereby adjusting the position of the guide plate 4.

[0055] In an optional embodiment of the present invention, the adjustment mechanism includes a telescopic device, one end of which is used to be rotatably connected to the arm frame 1, and the other end of the telescopic device is rotatably connected to the guide plate 4. In this way, the guide plate 4 can be driven to rotate by the extension and retraction of the telescopic device, thereby adjusting the position of the guide plate 4.

[0056] Specifically, the telescopic device may be located on a side of the guide plate 4 away from the luffing pulley frame 2 , so that the telescopic device can drive the guide plate 4 to rotate.

[0057] Here, the telescopic device can be an adjusting cylinder 5 or a pneumatic cylinder or an electric push rod or a compression spring, or other devices capable of achieving telescopic movement.

[0058] In this embodiment, if Figures 5 to 7As shown, the telescopic device is an adjusting cylinder 5, the cylinder body of the adjusting cylinder 5 is hinged to the boom 1, and the piston rod of the adjusting cylinder 5 is hinged to the guide plate 4. In addition, the adjusting mechanism may also include a hydraulic system for supplying oil to the adjusting cylinder 5, and the controller 10 is connected to the hydraulic system in communication so as to control the adjusting cylinder 5.

[0059] In another optional embodiment of the present invention, the adjustment mechanism includes a drive motor, which is arranged on the boom 1, and the output shaft of the drive motor is connected to the bottom end of the guide plate 4 through a rotating shaft, so that the guide plate 4 can be driven to rotate by the drive motor, so as to adjust the position of the guide plate 4. For example, in the process of lying down the arm, when the slot detection device detects that the variable amplitude pulley frame 2 is in the slot, the drive motor rotates forward, driving the guide plate 4 to swing toward the direction close to the boom 1, so that the guide plate 4 rotates to the second position (flat state); in the process of raising the arm, when the boom angle detection device detects that the angle between the boom 1 and the horizontal plane is greater than the preset angle, the drive motor reverses, driving the guide plate 4 to rotate (rotate in the direction away from the boom 1), so that the guide plate 4 rotates to the initial position (upward state).

[0060] In an optional embodiment of the present invention, two guide plates 4 and two adjusting mechanisms are provided, and the two guide plates 4 and the adjusting mechanisms are respectively arranged on opposite sides of the boom 1 to improve the stability and balance of the variable amplitude pulley frame 2 when entering the groove.

[0061] The working process of the luffing pulley frame slot adjustment device provided by the present invention is as follows:

[0062] When the boom 1 needs to be bent, the wire rope 3 is slowly released, and the roller 21 of the luffing pulley frame 2 falls on the guide plate 4. Figure 5 and Figure 6 As shown, at this time, the guide plate 4 is in the initial state (i.e., the guide plate 4 is in the upward state), and the luffing pulley frame 2 slides down the guide plate 4 into the groove under the action of gravity. When the detection element 6 on the guide plate 4 detects the roller 21 of the luffing pulley frame 2, it means that the luffing pulley frame 2 has reached the slot position (i.e., the slot is in place). After receiving the signal from the detection element 6, the controller 10 of the data processing system controls the adjustment cylinders 5 on both sides of the boom 1 to move (contract), so that the guide plates 4 on both sides rotate to the second position (i.e., rotate to the flat state), as shown in FIG. Figure 5 As shown, the luffing pulley frame 2 lies flat on the ear plate of the boom 1, so that the luffing pulley frame 2 can be smoothly inserted into the groove, meeting the requirements for transporting the crane mainframe with the boom 1.

[0063] When the boom 1 is raised, the main luffing wire rope 3 tightens the luffing pulley frame 2, and the angle sensor 8 detects the relative angle between the boom 1 and the horizontal plane. When the boom 1 is raised to a certain angle, that is, the angle between the boom 1 and the horizontal plane is greater than the preset angle (the angle between the boom 1 and the horizontal plane detected by the boom angle detection device when the luffing pulley frame 2 enters the groove in the process of raising the boom), the controller 10 of the data processing system, after receiving the signal transmitted by the boom angle detection device, controls the action (extension) of the adjustment cylinder 5 to return the guide plate 4 from the second position (flat state) to the initial position (upward state), so that the guide plate 4 can play the role of guiding support for the next luffing pulley frame 2 to enter the groove.

[0064] The boom assembly provided by the present invention is described below. The boom assembly described below and the variable amplitude pulley frame slot adjustment device described above can be referred to each other.

[0065] The present invention provides a boom assembly, comprising a boom 1, a luffing pulley frame 2, and a luffing pulley frame slot adjustment device as described in any of the above embodiments. The beneficial effects achieved by the boom are consistent with the beneficial effects achieved by the luffing pulley frame slot adjustment device provided by the present invention, and will not be described in detail here.

[0066] The crane provided by the present invention is described below. The crane described below and the boom assembly or the luffing pulley frame slot adjustment device described above can correspond to each other.

[0067] The present invention provides a crane, comprising a boom assembly as described in the above embodiments or a luffing pulley frame slot adjustment device as described in any of the above embodiments. The beneficial effects achieved by the crane are consistent with the beneficial effects achieved by the boom assembly or the luffing pulley frame slot adjustment device provided by the present invention, and will not be repeated here.

[0068] Here, the crane may be a crawler crane.

[0069] The device embodiments described above are merely illustrative, and some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. A person of ordinary skill in the art may understand and implement the present invention without creative effort.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for adjusting the entry of a luffing pulley frame into a slot, characterized in that: include: A guide plate, used for guiding the luffing pulley frame into the groove, wherein the first end of the guide plate is rotatably connected to the arm frame; An adjusting mechanism is arranged on the arm and connected to the guide plate, and the adjusting mechanism can drive the guide plate to swing in a direction close to or away from the arm; It also includes a slot detection device, which is used to detect whether the luffing pulley frame is in place in the slot; It also includes a boom angle detection device, which is used to detect the angle between the boom and the horizontal plane, and the boom angle detection device is communicatively connected with the adjustment mechanism, wherein when the boom angle detection device detects that the angle between the boom and the horizontal plane is greater than a preset angle, the adjustment mechanism drives the guide plate to rotate to an initial position, and the initial position is the position when the guide plate can guide the variable amplitude pulley frame into the groove.

2. The device for adjusting the luffing pulley frame into the groove according to claim 1, characterized in that: The slot detection device is in communication with the adjustment mechanism, wherein: When the slot-entry detection device detects that the luffing pulley frame is in place in the slot, the adjustment mechanism drives the guide plate to rotate in a direction close to the boom.

3. The device for adjusting the luffing pulley frame into the groove according to claim 2, characterized in that: The slot entry detection device comprises a detection element for detecting the roller position of the variable amplitude pulley frame, and the detection element is arranged on the guide plate.

4. The device for adjusting the luffing pulley frame into the groove according to claim 3, characterized in that: The detection element is arranged at the intersection of the arc and the guide surface of the guide plate or below the intersection, wherein the arc is a line constructed with the center of the pin hole of the ear plate of the arm as the center and the distance between the center of the roller and the center of the pin hole of the variable amplitude pulley frame as the radius.

5. The device for adjusting the luffing pulley frame into the groove according to claim 1, characterized in that: The adjusting mechanism comprises a telescopic device, one end of which is used for rotationally connecting with the arm support, and the other end of which is rotationally connected with the guide plate.

6. The device for adjusting the luffing pulley frame into the groove according to claim 1, characterized in that: The guide plates and the adjustment mechanisms are both provided with two and are respectively arranged on two opposite sides of the arm support.

7. The device for adjusting the luffing pulley frame into the groove according to claim 5, characterized in that: The telescopic device is an adjusting oil cylinder or an air cylinder or an electric push rod or a compression spring.

8. A boom assembly, characterized in that: The invention comprises a boom, a luffing pulley frame and a slot adjustment device for the luffing pulley frame as claimed in any one of claims 1 to 7.

9. A crane, characterized in that: It comprises the boom assembly as claimed in claim 8 or the slot adjustment device for the variable-length pulley frame as claimed in any one of claims 1 to 7.

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