Method and system for controlling a telescopic arm of a single-girder pin-lift crane

Abstract

The present application relates to the technical field of crane, and provides a telescopic arm control method and system of single-lever bolt crane, the telescopic arm control method comprising: receiving a first control instruction of arm extension; calculating a target length of telescopic arm; controlling each arm section to decelerate and run to the corresponding target position, and when the current arm section runs to the corresponding target position, controlling the arm pin of the current arm section to be inserted into the arm pin hole of the corresponding outer sleeve arm section; controlling the current arm section to retract until the arm pin contacts the lower end of the arm pin hole, completing the arm extension action of the current arm section; the present application retracts the current arm section by a certain distance after the arm extension is in place, so that the arm pin of the current arm section contacts the lower end of the arm pin hole, and when the subsequent telescopic arm is recycled, the current arm section needs to be pushed forward to facilitate the disconnection of the arm pin and the arm pin hole, so that the current arm section provides a bearing capacity, and thus there is no impact sound when the arm retraction action is performed again.

Description

Technical Field

[0001] The present invention relates to the technical field of cranes, and in particular to a telescopic arm control method and system of a horizontal bar latch crane. Background Art

[0002] Most multi-arm cranes use a single-cylinder latch-type telescopic mechanism, which realizes the telescopic function of the telescopic arm through the cooperation of the telescopic cylinder, cylinder pin, arm pin, and a cylinder-arm pin drive mechanism with a cylinder pin cylinder and an arm pin cylinder. The cylinder pin cylinder drives the cylinder pin to plug and pull out to control the locking or separation of the telescopic part of the telescopic cylinder and the arm section of the telescopic arm, and the arm pin cylinder drives the arm pin to plug and pull out to control the locking or separation of two adjacent arm sections. When a certain arm section needs to be extended, the cylinder pin cylinder first drives the cylinder pin to move, locking the telescopic cylinder and the arm section. Then the arm pin cylinder drives the arm pin to move, releasing the lock between the arm section and the previous arm section. The arm section then moves to the target position with the telescopic cylinder. Then, the arm pin is driven by the arm pin cylinder to move, locking the arm section and the previous arm section to the target position. Then, the cylinder pin cylinder drives the cylinder pin to move, releasing the lock between the telescopic cylinder and the arm section. And so on to realize the telescopic function.

[0003] At present, the horizontal bar latch models of automobile cranes on the market generally have a significant impact phenomenon at the moment of boom retraction, especially when the second and third boom sections are retracted in the fully extended state. The impact at the start is relatively large. The existing method for dealing with the impact problem is mainly to set the deceleration distance when the telescopic boom is started and when it is about to reach the target position, and reduce the operating speed when the movement reaches the target position range to reduce the impact phenomenon. However, at the moment of boom retraction, since the telescopic control valve is an on-off valve, the valve opens instantly when it is energized, and the system flow increases suddenly, making it difficult to control the movement speed of the cylinder. In addition, there is a large gap between the arm pin and the arm pin hole, causing the arm section to fall onto the arm pin due to gravity, resulting in an impact at the moment of boom retraction. Summary of the Invention

[0004] The present invention provides a telescopic arm control method and system for a horizontal bar latch crane, which are used to solve the problem of boom section impact at the moment of boom retraction and opening in the prior art.

[0005] The present invention provides a telescopic arm control method of a horizontal bar latch crane, comprising:

[0006] receiving a first control instruction for extending the arm;

[0007] Calculate the target length of the telescopic arm;

[0008] Control each boom section to decelerate and run to the corresponding target position, and when the current boom section runs to the corresponding target position, control the arm pin of the current boom section to be inserted into the arm pin hole of the corresponding outer boom section;

[0009] The current arm section is controlled to retract until the arm pin contacts the lower end of the arm pin hole, thereby completing the arm extension action of the current arm section.

[0010] According to the telescopic boom control method of the horizontal bar latch crane provided by the present invention, the control of each boom section to decelerate and run to the corresponding target position includes:

[0011] The distance between the currently moving boom section and the target position is obtained in real time. When the distance meets the preset distance, the currently moving boom section is controlled to decelerate and move to the corresponding target position.

[0012] According to the telescopic arm control method of the horizontal bar latch crane provided by the present invention, when the distance meets the preset distance, controlling the current boom section to decelerate and move to the corresponding target position includes:

[0013] When the distance meets the first preset distance, the current boom section is decelerated to the first level and continues to move toward the target position;

[0014] When the distance meets the second preset distance, a secondary deceleration process is adopted for the current boom section until the current boom section runs to the target position.

[0015] The telescopic arm control method of the horizontal bar latch crane provided by the present invention further includes:

[0016] receiving a second control instruction for retracting the arm;

[0017] Controlling the arm segment that currently needs to execute the instruction to extend forward, and after the extension, releasing the connection between the arm pin of the arm segment and the arm pin hole of the outer arm segment;

[0018] Controlling the current boom section to retract at a first speed until the current boom section runs to a set distance;

[0019] The current boom section is controlled to operate normally at a second speed to complete a retraction start operation of the current boom section, wherein the second speed is greater than the first speed.

[0020] According to the telescopic arm control method of the horizontal bar latch crane provided by the present invention, the first speed is less than or equal to 5 m / s.

[0021] According to the telescopic arm control method of the horizontal bar latch crane provided by the present invention, each arm section is provided with four arm pin holes at intervals along its length direction.

[0022] In a second aspect, the present invention further provides a telescopic arm control system for a horizontal bar latch crane, comprising: a telescopic arm and a control unit, wherein the control unit is configured to execute the telescopic arm control method for the horizontal bar latch crane as described in the first aspect.

[0023] The telescopic arm control system of the horizontal bar latch crane provided by the present invention also includes:

[0024] A telescopic oil cylinder is provided on the basic arm of the telescopic arm, and a cylinder pin is provided radially on the driving rod of the telescopic oil cylinder, and the cylinder pin is used to cooperate with the cylinder pin socket at the tail of each section of the telescopic arm;

[0025] An arm pin is provided on the outer peripheral wall of the tail end of each section of the telescopic arm, and the arm pin can be plugged into and matched with the arm pin hole of the telescopic arm of the outer sleeve to fix two adjacent sections of the telescopic arm;

[0026] The overflow valve is used to adjust the system oil pressure flowing through the telescopic arm and to buffer the impact between the arm pin and the arm pin hole at the moment when the telescopic arm starts to retract.

[0027] The telescopic arm control system of the horizontal bar latch crane provided according to the present invention also includes: a proportional main valve, which is connected to the telescopic cylinder and is used to control the flow of hydraulic oil in and out of the telescopic cylinder to control the extension or retraction speed of each section of the telescopic arm.

[0028] According to the telescopic arm control system of the horizontal bar latch crane provided by the present invention, the proportional main valve includes an extension arm proportional solenoid valve and a retraction arm proportional solenoid valve.

[0029] The present invention provides a telescopic boom control method and system for a horizontal bar latch crane. After the boom is fully extended, the front boom section is retracted a certain distance so that the arm pin of the front boom section contacts the lower end of the arm pin hole. When the telescopic boom is subsequently retracted, the telescopic cylinder needs to push the boom section forward to facilitate the disconnection of the arm pin from the arm pin hole. In this way, when the telescopic cylinder pushes the boom section forward, it provides bearing capacity to the boom section, so that there is no impact sound when the boom is retracted. In addition, the telescopic cylinder is not subjected to pressure during lifting, which plays a protective role for the telescopic cylinder. The pressure in the system is controlled by adding a relief valve. The proportional control characteristics of the relief valve are utilized to enable the opening of the relief valve to be accurately set within the range of 0-100%. The relief valve can adjust its relief capacity as needed, thereby achieving precise regulation of the system pressure, controlling the pressure fluctuation range in the system, making the system more stable, and effectively reducing the pressure fluctuation at the moment of boom retraction, avoiding system vibration and noise caused by pressure fluctuation, and effectively eliminating the jitter phenomenon at the moment of boom retraction startup, making the system operation more stable and smooth. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0031] Figure 1 The present invention provides a flowchart of a telescopic arm control method for a horizontal bar latch crane.

[0032] Figure 2 It is a flow chart of a telescopic arm control method of a horizontal bar latch crane provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0034] The following combination Figure 1-Figure 2 The present invention describes a telescopic arm control method and system of a horizontal bar latch crane.

[0035] The invention provides a telescopic arm control system of a horizontal bar latch crane, comprising a telescopic oil cylinder, an arm pin, a relief valve and a control unit.

[0036] Specifically, the telescopic cylinder is arranged on the basic arm of the telescopic arm, and the driving rod of the telescopic cylinder is radially provided with a cylinder pin, which is used to cooperate with the cylinder pin socket at the tail of each telescopic arm section; the arm pin is arranged on the outer peripheral wall at the tail of each telescopic arm section, and the arm pin can be plugged and matched with the arm pin hole of the telescopic arm of the outer sleeve to fix the two adjacent telescopic arms; the overflow valve adopts an electric proportional valve to adjust the system oil pressure flowing through the telescopic arm, and is used to buffer the impact between the arm pin and the arm pin hole at the moment of starting the retraction action of the telescopic arm.

[0037] It should be noted that the basic arm of the telescopic arm usually refers to the fixed part of the telescopic arm. As the starting part of the telescopic arm, it provides support for the subsequent telescopic arm sections. The basic arm is a product in the existing technology. Its structure and principle are not the focus of this article and will not be discussed here.

[0038] The present application controls the pressure in the system by adding an overflow valve, and uses the proportional control characteristics of the overflow valve to accurately set its opening degree in the range of 0-100%. For example, when the opening degree is 0%, the overflow valve is completely closed, and the system pressure will continue to rise. In this setting, the overflow valve does not participate in pressure control. When the opening degree is 100%, the overflow valve is completely open, and the system pressure will quickly decrease to the tank pressure or close to the tank pressure. At this time, the overflow valve plays the largest overflow role. When the opening degree is between 0% and 100%, the overflow valve can adjust its overflow capacity as needed to accurately regulate the system pressure, control the pressure fluctuation range in the system, make the system more stable, effectively reduce the fluctuation of the arm retraction instantaneous pressure, avoid system vibration and noise caused by pressure fluctuation, effectively eliminate the arm shaking phenomenon, and make the system run more smoothly and smoothly.

[0039] While maintaining the stability of the system pressure, the overflow valve can also reduce unnecessary energy loss. When the system pressure is too high, the excess hydraulic oil will flow back to the tank through the overflow valve instead of continuing to circulate in the system to consume energy.

[0040] Further, a proportional main valve is also included, which is connected with the telescopic oil cylinder and used to control the flow of hydraulic oil in and out of the telescopic oil cylinder to control the extension or retraction speed of each telescopic arm.

[0041] In this embodiment, the proportional main valve includes an extension proportional electromagnetic valve and a retraction proportional electromagnetic valve. The extension proportional electromagnetic valve is connected with the rod cavity of the telescopic oil cylinder and can proportionally control the flow and pressure of hydraulic oil to accurately control the extension action. The retraction proportional electromagnetic valve is connected with the rodless cavity of the telescopic oil cylinder and can proportionally control the flow and pressure of hydraulic oil to accurately control the retraction action.

[0042] In some embodiments, the overflow valve can be arranged in the oil circuit between the hydraulic pump and the telescopic oil cylinder. The pressure oil port of the overflow valve is directly connected to the output end of the hydraulic pump for receiving the pressure oil provided by the hydraulic pump. The oil return port of the overflow valve is connected to the tank, and the excess oil can flow back to the tank through the overflow valve. In addition, the overflow valve is also connected with the controller of the control unit and the like to monitor and adjust the system pressure in real time.

[0043] The present embodiment provides a telescopic arm control method of a single-lever bolt hoist, which comprises:

[0044] Step 101: receiving a first control instruction of the extension arm.

[0045] Optionally, the first control instruction can be obtained through one or more communication methods in the prior art, for example, it can be a control instruction from a human-machine interaction interface with a soft switch on the hoist; or a control instruction sent by a remote intelligent driving system.

[0046] Step 102: Calculate the target length of the telescopic arm, that is, the length of the telescopic arm when performing the telescopic action to the target. For example, the extended length of the telescopic arm is calculated based on the distance between the crane and the location of the working target. Based on the extended length of the telescopic arm, the control unit calculates the number of arm sections to be extended and the extended length of each arm section, so that the sum of the lengths of the arm sections is the target length of the telescopic arm.

[0047] Step 103: Control each boom segment to decelerate and move to the corresponding target position, and when the current boom segment moves to the corresponding target position, control the arm pin of the current boom segment to be inserted into the arm pin hole of the corresponding outer boom segment.

[0048] In this embodiment, the control unit controls the driving rod of the telescopic cylinder to drive the arm section to be moved to extend outward, and adjusts the opening of the arm proportional solenoid valve through the control unit. For example, the opening is adjusted to 80% of the normal action opening to reduce the oil pressure and oil volume entering the rod chamber of the telescopic cylinder, so as to realize the deceleration operation of the current arm section driven by the telescopic cylinder. During this process, the overflow valve is in a fully open state.

[0049] Step 104: Control the current boom section to retract until the arm pin contacts the lower end of the arm pin hole, completing the arm extension action of the current boom section.

[0050] In this embodiment, the opening of the relief valve is maintained, and the opening of the arm retraction proportional solenoid valve is reduced by the control unit, so that the arm pin of the current arm section moves to the lower end of the arm pin hole (minimum value), and the arm retraction action is stopped.

[0051] With this arrangement, after the arm is extended into place, the front arm section is retracted a certain distance so that the arm pin of the front arm section contacts the lower end of the arm pin hole. When the telescopic arm is subsequently recovered, the telescopic cylinder needs to push the arm section forward to facilitate the disconnection of the arm pin from the arm pin hole. In this way, when the telescopic cylinder pushes the arm section forward, it will provide bearing capacity to the arm section, so that there will be no impact sound when the arm is retracted. In addition, the telescopic cylinder will not be under pressure during lifting, which has a protective effect on the telescopic cylinder.

[0052] It should be noted that the arm pin hole on the telescopic arm of a crane usually has a large reserved position. After the arm pin is inserted into the hole, there will be a large reserved space above and below (usually 30 to 100 mm). The existence of the reserved space makes the specific position of the arm pin in the arm pin hole uncertain after the arm is extended into place. By retracting the current arm section, the arm pin is made to abut against the lower end of the arm pin hole.

[0053] Furthermore, controlling each boom section to decelerate and run to the corresponding target position in step 103 includes: obtaining the distance from the currently moving boom section to the target position in real time, and when the distance meets the preset distance, controlling the current boom section to decelerate and run to the corresponding target position.

[0054] In this embodiment, the target position refers to when the arm pin of the current arm section moves to the target hole position (arm pin hole) of the outer arm section so that the elongation of the current arm section meets the elongation requirement. After reaching the target position, the arm pin of the arm section must be locked with the target hole position to prevent slipping.

[0055] Optionally, each arm section is provided with four arm pin holes at intervals along its length, which are respectively arranged at 0%, 46%, 92% and 100% of the total length of the arm section, where 0% indicates full retraction and 100% indicates full extension. The control unit calculates the length of each arm section according to the total length that the telescopic arm needs to be extended, that is, the target hole position where the arm pin of each arm section should be locked.

[0056] Furthermore, when the distance meets the first preset distance, the current arm section is subjected to a first-level deceleration process and continues to move toward the target position; when the distance meets the second preset distance, the current arm section is subjected to a second-level deceleration process until the current arm section reaches the target position.

[0057] In some embodiments, the first preset distance is 700m, the second preset distance is 300m, and the first deceleration is started at 700mm away from the target hole position, which can be achieved by adjusting the opening of the arm proportional solenoid valve to about 80% of the normal action opening, or by reducing the pump current when a pump control system is used. The overflow valve is fully open at this stage; when the distance from the target hole position is 300mm, the second deceleration is started, which can be achieved by reducing the opening of the arm proportional solenoid valve to 50% of the normal action opening, or by turning off the pump current output when a pump control system is used, and at the same time controlling the opening of the overflow valve to limit the operating speed of the telescopic cylinder, so that it slides to the target hole position at a speed not exceeding 10mm / s, inserting the arm pin, and then closing the arm proportional solenoid valve to stop the arm action.

[0058] In this embodiment, after the telescopic arm extension action is completed, the telescopic arm control method of the horizontal bar latch crane further includes:

[0059] Step 201: Receive the second control instruction for retracting the arm. This step is the same as the above step 101, and the implementation process will not be repeated here.

[0060] Step 202: Control the arm segment that currently needs to execute the instruction to extend forward, and release the connection between the arm pin of the arm segment and the arm pin hole of the outer arm segment after the extension.

[0061] Because the arm pin of the current arm section contacts with the lower end of the arm pin hole after the stretching arm is in place, when the arm retracting action is performed, the telescopic oil cylinder needs to push the current arm section forward first, so as to disconnect the arm pin and the arm pin hole, thus, when the telescopic oil cylinder pushes the current arm section forward, the current arm section is provided with a bearing force, so that when the arm retracting action is performed, there is no impact sound, in addition, the telescopic oil cylinder can not bear pressure when lifting, and the protection effect of the telescopic oil cylinder is achieved.

[0062] Step 203: control the current arm section to retract at a first speed until the current arm section runs to a set distance; for example, the first speed is less than or equal to 5 m / s.

[0063] In the embodiment, when the arm retracting is prepared, the opening of the overflow valve is adjusted to a small value, and the opening of the arm retracting proportional electromagnetic valve is adjusted to a small value, so that the impact caused by the gap between the arm pin and the arm pin hole is avoided when the arm retracting is started, and the current arm section slowly runs to the set distance at a speed not greater than 5 m / s.

[0064] Step 204: control the current arm section to normally run at a second speed to complete the arm retracting starting operation of the current arm section, and the second speed is greater than the first speed.

[0065] In this way, after the current arm section runs to the set distance, the opening of the arm retracting proportional electromagnetic valve is slowly increased to a normal value at a certain step, the arm retracting starting operation is completed, and the whole process does not produce impact, and the vehicle body is stable.

[0066] The embodiment of the application provides a telescopic arm control system of a single-bar bolt hoist, which comprises:

[0067] The telescopic arm and the control unit are used to execute the telescopic arm control method of the single-bar bolt hoist.

[0068] Specifically, the control unit comprises at least one processor and at least one memory in communication connection with the processor, wherein the memory stores program instructions executable by the processor, and the processor calling the program instructions can execute the container transport vehicle control method.

[0069] The control method of the present invention can be executed as a software program or computer instruction in a non-transitory computer-readable storage medium or in a control system with a memory and a processor, and its calculation program is simple and runs fast. The functional units in the various embodiments of the present invention can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of hardware plus software functional units. The above-mentioned integrated unit implemented in the form of a software functional unit can be stored in a computer-readable storage medium. The above-mentioned software functional unit is stored in a storage medium, including several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to perform some steps of the method described in the various embodiments of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0070] An embodiment of the present invention also provides a crane including the aforementioned horizontal-bar latch crane telescopic boom control system. The crane can be a single-cylinder latch crane of 80 tons or greater. By employing the aforementioned horizontal-bar latch crane telescopic boom control system, the impact of starting to retract the boom and extending it to its full extent can be resolved, providing the aforementioned advantages.

[0071] In the description of the embodiments of the present invention, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; and direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on specific circumstances.

[0072] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "aspects", "specific aspects", or "some aspects" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or aspect are included in at least one embodiment or aspect of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or aspect. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or aspects. In addition, different embodiments or aspects described in the specification and the features of different embodiments or aspects can be combined and combined by those skilled in the art without contradiction, if necessary.

[0073] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A telescopic arm control method for a horizontal bar latch crane, characterized in that: include: receiving a first control instruction for extending the arm; Calculate the target length of the telescopic arm; Control each boom section to decelerate and run to the corresponding target position, and when the current boom section runs to the corresponding target position, control the arm pin of the current boom section to be inserted into the arm pin hole of the corresponding outer boom section; The current arm section is controlled to retract until the arm pin contacts the lower end of the arm pin hole, thereby completing the arm extension action of the current arm section.

2. The telescopic arm control method of the horizontal bar latch crane according to claim 1, characterized in that: The controlling of each boom section to decelerate and move to the corresponding target position includes: The distance between the currently moving boom section and the target position is obtained in real time. When the distance meets the preset distance, the currently moving boom section is controlled to decelerate and move to the corresponding target position.

3. The telescopic arm control method of the horizontal bar latch crane according to claim 2, characterized in that: When the distance meets the preset distance, controlling the current boom section to decelerate and move to the corresponding target position includes: When the distance meets the first preset distance, the current boom section is decelerated to the first level and continues to move toward the target position; When the distance meets the second preset distance, a secondary deceleration process is adopted for the current boom section until the current boom section runs to the target position.

4. The telescopic arm control method of the horizontal bar latch crane according to claim 1 or 2, characterized in that: Also includes: receiving a second control instruction for retracting the arm; Controlling the arm segment that currently needs to execute the instruction to extend forward, and after the extension, releasing the connection between the arm pin of the arm segment and the arm pin hole of the outer arm segment; Controlling the current boom section to retract at a first speed until the current boom section runs to a set distance; The current boom section is controlled to operate normally at a second speed to complete a retraction start operation of the current boom section, wherein the second speed is greater than the first speed.

5. The telescopic arm control method of the horizontal bar latch crane according to claim 4, characterized in that: The first speed is less than or equal to 5 m / s.

6. The telescopic arm control method of a horizontal bar latch crane according to claim 1, characterized in that: Each arm section is provided with four arm pin holes at intervals along its length direction.

7. A telescopic arm control system for a horizontal bar latch crane, characterized in that: include: A telescopic arm and a control unit, wherein the control unit is used to execute the telescopic arm control method of a horizontal bar latch crane according to any one of claims 1 to 6.

8. The telescopic arm control system of the horizontal bar latch crane according to claim 7, characterized in that: Also includes: A telescopic oil cylinder is provided on the basic arm of the telescopic arm, and a cylinder pin is provided radially on the driving rod of the telescopic oil cylinder, and the cylinder pin is used to cooperate with the cylinder pin socket at the tail of each section of the telescopic arm; An arm pin is provided on the outer peripheral wall of the tail end of each section of the telescopic arm, and the arm pin can be plugged into and matched with the arm pin hole of the telescopic arm of the outer sleeve to fix two adjacent sections of the telescopic arm; The overflow valve is used to adjust the system oil pressure flowing through the telescopic arm and to buffer the impact between the arm pin and the arm pin hole at the moment when the telescopic arm starts to retract.

9. The telescopic arm control system of the horizontal bar latch crane according to claim 7, characterized in that: It also includes a proportional main valve, which is connected to the telescopic cylinder and is used to control the flow of hydraulic oil in and out of the telescopic cylinder to control the extension or retraction speed of each section of the telescopic arm.

10. The telescopic arm control system of the horizontal bar latch crane according to claim 9, characterized in that: The proportional main valve includes an arm extension proportional solenoid valve and an arm retraction proportional solenoid valve.

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