A stacker

Abstract

The present application provides a kind of stacker, including first fork and second fork arranged side by side, the first fork and second fork have the detection surface in the most front end along its extension direction, further comprising: a plurality of conductive strips, respectively set in the side wall of each layer cross bar of goods shelf towards fork, the conductive strip extends along the length direction of goods shelf;Collision detection circuit, including first electrically conductive body and second electrically conductive body, the first electrically conductive body, second electrically conductive body and the conductive strip are cooperated to form contact switch;The first electrically conductive body is arranged on the detection surface of first fork, and the second electrically conductive body is arranged on the detection surface of second fork;When first fork and second fork extend towards goods shelf, make first electrically conductive body, second electrically conductive body simultaneously contact and electrically connected with the conductive strip, and collision detection circuit is closed and sends out alarm.The stacker of the present application can effectively avoid rigid collision, realize the real-time detection and automatic deviation correction of collision.

Description

Technical Field

[0001] This invention relates to the field of warehousing technology, and in particular to a stacker crane. Background Technology

[0002] Automated storage and retrieval systems (AS / RS) are intelligent warehousing systems that utilize high-rise racking to store goods and employ automated equipment such as stacker cranes for storage and retrieval operations. For example... Figure 1 As shown, the automated storage and retrieval system includes high-rise racks 1, multiple stacker cranes 2, and a conveyor system 3. The high-rise racks are composed of multiple rack groups arranged side by side. Each rack group includes two sets of racks 1 arranged opposite each other. An aisle is formed between the two sets of racks 1 for the stacker cranes 2 to operate. A conveyor track 4 is laid in the middle of the ground in the aisle.

[0003] Stacker crane 2 is located within the aisle, with a traveling mechanism mounted at its bottom that runs along conveyor track 4. A vertically extending column is fixed to the traveling mechanism, and a loading platform and a lifting motor that drives the loading platform to move up and down along the column are mounted on the column. Extendable forks are installed on the loading platform for picking up palletized goods (i.e., pallets and the goods stacked on them). The racking has multiple storage locations, with the entrance to each location facing the corresponding stacker crane.

[0004] Currently, stacker cranes generally use address plate positioning: address plates are arranged at equal intervals along the rack or the ground, and slotted photoelectric switches are installed on the loading platform to detect the address plates. Each time an address plate is passed, the address is incremented (or decremented) and the counted address is compared with the theoretical address of the target storage location to achieve positioning of the loading platform in the horizontal and vertical directions.

[0005] However, in actual operation, collisions can easily occur between the forks and the racks or goods, especially in storage operations. When the forks extend into the storage location, they may interfere with and collide with the rack beams, causing damage to the rack structure and causing palletized goods to tip over. Summary of the Invention

[0006] Based on this, the purpose of the present invention is to overcome the defects or deficiencies of the prior art and provide a stacker crane, including a first fork and a second fork arranged side by side, the first fork and the second fork having a detection surface located at the foremost end along their extension direction, and further including: Multiple conductive strips are respectively installed on the side wall of each layer of the shelf facing the forks, and the conductive strips extend along the length of the shelf; The collision detection circuit includes a first conductor and a second conductor, wherein the first conductor, the second conductor, and the conductive strip cooperate to form a contact switch; The first conductor is disposed on the detection surface of the first fork, and the second conductor is disposed on the detection surface of the second fork; when the first fork and the second fork extend toward the shelf, and the first conductor and the second conductor simultaneously contact and are electrically connected with the conductive strip, the collision detection circuit closes and issues an alarm.

[0007] Compared to existing technologies, this invention provides a conductor at the end of the fork and a conductive strip on the crossbar of the shelf. When there is an error between the actual position and the theoretical position of the fork, the conductor and the conductive strip come into contact, causing the collision detection circuit to close and generate a closing signal, thus detecting the position deviation in a timely manner and effectively avoiding rigid collisions between the fork and the shelf or goods.

[0008] In one embodiment, a controller is also included for controlling the lifting and extension of the first and second forks; the controller is communicatively connected to the collision detection circuit, and when the collision detection circuit is closed, it sends a closing signal to the controller, which then controls the first and second forks to rise until the closing signal disappears.

[0009] In one embodiment, when the first fork and the second fork extend toward the target storage location on the shelf, the controller controls the first fork and the second fork to extend synchronously at a first speed; If a closing signal is received from the collision detection circuit, the first and second forks are controlled to rise until the closing signal disappears. Then, the first and second forks are controlled to stop rising and resume normal extension speed to continue extending. If no closing signal is received from the collision detection circuit, the first and second forks are controlled to continue extending at a first speed until their extension distance is greater than a preset distance. Then, the first and second forks are controlled to return to the normal extension speed and continue extending. The preset distance is greater than or equal to the distance between the initial position of the forks and the vertical plane where the entrance of the target cargo position is located, and the first speed is less than the normal extension speed.

[0010] In one embodiment, if a closed signal of the collision detection circuit is received, and if the controller receives the closed signal of the collision detection circuit during the process of the first fork and the second fork extending toward the shelf, then the controller controls the first fork and the second fork to stop extending and start lifting until the closed signal disappears. Then the controller controls the first fork and the second fork to stop lifting and resume normal extension speed to continue to extend synchronously.

[0011] In one embodiment, the detection surface of the conductive strip is an inclined or curved surface that slopes downwards away from the crossbar; or, the detection surface of the conductive strip is a vertical plane and the conductive strip is elastically connected to the crossbar by several buffer springs. If the controller receives a closed signal from the collision detection circuit during the extension of the first and second forks toward the shelf, it controls the first and second forks to continue extending at a speed less than or equal to the first speed, and simultaneously begins to lift until the closed signal disappears. Then, it controls the first and second forks to stop lifting and resume to the normal extension speed to continue extending synchronously.

[0012] In one embodiment, if the lifting height of the first fork and the second fork reaches a preset threshold during the duration of the closing signal and the closing signal has not disappeared, the controller controls the first fork and the second fork to stop moving and issues an alarm.

[0013] In one embodiment, the outer periphery of the first conductor and the second conductor are respectively provided with axially expandable protective sleeves. The protective sleeves are compressed under pressure to expose the corresponding conductors. After the pressure is removed, the protective sleeves are reset and wrap around the corresponding conductors.

[0014] In one embodiment, the first conductor and the second conductor are electrode posts that can elastically expand and contract along the axial direction; in the natural state, the front end face of the protective sleeve protrudes from the top of the corresponding electrode post; the protective sleeve has a maximum axial compression amount, which is greater than the distance between the top of the electrode post and the front end face of the protective sleeve.

[0015] In one embodiment, the drive mechanism includes a drive motor and a first transmission wheel and a second transmission wheel that are drively connected to the drive motor; both the first fork and the second fork include a fixed frame, a middle fork slidably connected to the fixed frame, and an upper fork slidably connected to the middle fork; each middle fork has a first rack extending along its length at its bottom, and at least one gear is rotatably connected to each middle fork; the first rack of the first fork meshes with the first transmission wheel for transmission, and the first rack of the second fork meshes with the second transmission wheel for transmission; each upper fork has a second rack extending along its length, and the second rack meshes with the gear of the corresponding middle fork for transmission.

[0016] In one embodiment, each middle fork is provided with a conductive area extending along its length; each fixed frame is provided with a fixed frame conductive spring that is electrically connected to the collision detection circuit, and the fixed frame conductive spring slides against the conductive area of ​​the corresponding middle fork; each upper fork is provided with an upper fork conductive spring that slides against the conductive area of ​​the corresponding middle fork; the first conductor and the second conductor are respectively provided at the upper fork end of the corresponding fork and are respectively electrically connected to the corresponding upper fork conductive spring.

[0017] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an existing automated storage and retrieval system.

[0019] Figure 2 This is a schematic diagram of the stacker crane of the present invention.

[0020] Figure 3 for Figure 2 A top view of the forklift mechanism.

[0021] Figure 4 for Figure 2 A schematic diagram of the structure of the conductive sheet.

[0022] Figure 5 This is a schematic diagram of a collision detection circuit according to one embodiment.

[0023] Figure 6 This is a schematic diagram of a collision detection circuit according to one embodiment.

[0024] Figure 7 This is a schematic diagram of the fork-taking mechanism in one embodiment.

[0025] Figure 8 for Figure 7 A schematic diagram of the structure in which the fork-shaped mechanism abuts against the conductive sheet.

[0026] Figure 9 for Figure 8 A magnified view of a portion of the image.

[0027] Figure 10 This is a schematic diagram of the collision detection mechanism according to one embodiment.

[0028] Figure 11 for Figure 2 A schematic diagram of the forklift mechanism.

[0029] Figure 12 for Figure 7 A schematic diagram of the structure with the first fork extended.

[0030] Figure 13 for Figure 7 A schematic diagram of the exploded structure of the first fork.

[0031] Figure 14 for Figure 2 A schematic diagram of the walking mechanism.

[0032] In the diagram: 1. High-rise rack; 2. Stacker crane; 3. Conveying system; 4. Conveying track; 11. Rack unit; 111. Upright; 112. First crossbar; 113. Second crossbar; 12. Ground rail; 20. Traveling mechanism; 21. Base; 22. Traveling wheels; 23. Traveling motor; 24. Guide wheel; 30. Lifting mechanism; 31. Column; 32. Top plate; 33. Lead screw; 34. Servo motor; 40. Forklift mechanism; 41. Loading platform; 42. First fork; 42. Fixed frame; 421. Third rack; 4211. First sliding structure; 4212. Fixed frame conductive spring; 4213. Middle fork; 422. Base plate; 4221. First rack; 4222. Gear; 4223. First groove; 4224. Second groove 4225, conductive area 4226, upper fork 423, top plate 4231, side plate 4232, second rack 4233, second sliding structure 4234, upper fork conductive spring 4235, second fork 43, drive mechanism 44, drive motor 441, drive wheel 442, first transmission wheel 443, transmission rod 444, second transmission wheel 445; collision detection mechanism 50, conductive strip 51, insulating structure 511, first conductor 52, second conductor 53, buffer spring 54, telescopic cylinder 55, inner cylinder 551, outer cylinder 552, through hole 553, spring 554, columnar electrode 555; ceiling rail 60; controller 70. Detailed Implementation

[0033] To accurately pinpoint the root cause of the problem of fork tip collisions with shelves or goods, this invention first systematically investigated the stacker crane's operating parameters. It was confirmed that the address plate positioning method used by the stacker crane ensures accurate correspondence between the actual position of the loading platform and the theoretical address of the target storage location, thus eliminating the possibility of missed detection or inaccurate counting of address plates due to excessive operating speed. In other words, the loading platform's position control is precise, but the collision problem still exists. This prompted this invention to shift its analytical focus from overall positioning error to local positional deviations, thereby conducting a deeper investigation into the underlying mechanisms.

[0034] Further mechanistic analysis reveals that the core root cause of the collision problem lies in the inherent blind spot of the location identification method: this method can only detect the position of the loading platform itself and calculate the correspondence between the fork tip and the storage location entrance based on the theoretical relative position of the loading platform and the fork tip, but it cannot directly reflect the actual spatial position of the fork tip. Under actual working conditions, this indirect calculation is subject to multiple distortion factors, including the downward elastic deformation of the fork tip due to the weight of the palletized goods when the load is too heavy (i.e., the fork tip tilting), the change in the relative position of the fork tip caused by wear or loosening of the fork structure after long-term operation, and the swaying of the fork tip caused by mechanical vibration during operation. The combination of these factors causes the actual position of the fork tip to systematically deviate from the theoretical position, thus causing misalignment with the storage location entrance; in storage operations, if the fork tip is lower than the actual lower edge of the storage location entrance, the fork will interfere with and collide with the rack beam, causing minor damage to the rack structure, or even leading to the tipping of goods or equipment failure.

[0035] To address the collision problem caused by fork tip position deviation, existing technologies primarily employ a pre-emptive, precise sensing approach. This involves adding auxiliary positioning devices such as laser rangefinders and vision sensors to the stacker crane, using real-time detection of the relative distance between the fork tip and the storage location for position correction. However, this solution not only requires additional high-precision sensors, data processing units, and complex calibration algorithms to existing stacker cranes, resulting in high hardware costs, but also suffers from poor environmental adaptability due to the extreme sensitivity of laser and vision systems to dust and vibration conditions within the aisles. Furthermore, the complexity of data processing and system debugging makes direct modification and implementation on existing automated storage and retrieval systems (AS / RS) impractical and uneconomical. Therefore, while theoretically feasible, this approach faces significant limitations in large-scale industrial application and cannot become a universally applicable engineering solution.

[0036] Based on this, the present invention represents a crucial shift in thinking: since precise pre-collision sensing is difficult to overcome in terms of cost and feasibility of modification, why not lower the sensing accuracy requirements and shift the detection point from pre-collision prevention to post-collision loss mitigation, achieving collision protection with a simpler and more reliable solution? Following this approach, the present invention installs a pressure sensor at the front end of the forks. By detecting the collision pressure, the sensor transmits the signal to the controller, which then stops the stacker crane to prevent damage to the racking system from hard collisions. This solution achieves timely response after a collision with lower cost and a simpler structure, aiming to ensure racking safety while avoiding the deployment difficulties of high-precision sensors.

[0037] However, after the solution was put into actual operation, its application defects were quickly exposed: because the pressure sensor is extremely sensitive to contact force, even slight contact caused by pallet position displacement or conveyor line vibration when the stacker crane is picking up and placing pallets on the conveyor system during normal operation can be identified as a collision, leading to frequent false triggers. Once a false trigger occurs, the machine will stop, requiring the stacker crane to be reset, manually checked, and restarted. This not only seriously affects the continuous operation efficiency of the automated warehouse, but also has an adverse effect on the mechanical structure of the stacker crane due to the frequent start-stop impacts. Therefore, this invention realizes that the problem is not the lack of sensor accuracy, but the architecture itself that concentrates the detection function on a single end of the forks—this architecture cannot distinguish between normal operational contact and abnormal collision contact, falling into the dilemma of stopping the line immediately upon protection.

[0038] Faced with this dilemma, the present invention underwent a second crucial shift in approach: instead of focusing on adding more sophisticated sensors to the fork body to improve detection accuracy, it fundamentally restructured the detection architecture, disassembling the collision detection function and distributing it to both ends of the rack and forks. Specifically, conductive strips are installed on the crossbeams of the rack facing the aisle, and first and second conductors are respectively installed at the fork ends of the first and second forks arranged side by side, forming a circuit breaker for the collision detection circuit. The key to this design is that a conductive path is only formed between the first conductor, the conductive strip, and the second conductor when both the first and second forks extend into the rack area simultaneously and both conductors are in contact with the conductive strips on the rack crossbeams, thus closing the collision detection circuit and sending a signal.

[0039] Compared to solutions that place pressure sensors on the forks, this dual-end collaborative detection architecture of the rack and forks offers significant advantages in preventing accidental triggering. Because the conductive strip is fixed to the rack beams, the forks never come into contact with the conductive strips when normally picking up or placing pallets on the conveyor system. Detection triggering is strictly limited to the specific spatial scenario of the forks entering the rack area, fundamentally avoiding false triggering caused by pallet shifting or conveyor vibration. Simultaneously, circuit continuity relies on two conductors simultaneously contacting the conductive strip. If a person or insulating material accidentally touches a single fork electrode, a complete conductive circuit cannot be formed, and no detection signal will be triggered. Furthermore, the electrodes can be powered by a safe voltage, posing no safety risk even if a person makes single-point contact. This solution requires no complex algorithm calibration, is naturally immune to harsh working conditions such as dust and vibration, and only requires adding conductive strips to the rack beams and electrodes to the fork ends, resulting in extremely low modification costs. It can be directly implemented on existing automated storage and retrieval systems, combining economic efficiency and feasibility.

[0040] However, the inventors further realized that if the detection signal is only used to trigger a shutdown alarm, although hard collisions can be avoided, it will still lead to work interruption and fails to fundamentally solve the problem of how to efficiently resume work after a collision is detected. Detection is only a means; continuous operation is the goal. Therefore, the control logic of the detection signal must be re-examined. Based on this, the present invention further improves upon the above-mentioned collision detection scheme by setting up a controller. After receiving the closed signal of the collision detection circuit, the controller does not control the stacker crane to stop abruptly, but instead controls the forks to stop extending or reduce the extension speed. At the same time, it controls the lifting motor to drive the loading platform upward until the first and second conductors disengage from the conductive strip and the collision detection circuit is disconnected. Then, it controls the forks to continue the extension and retraction operation. Thus, the stacker crane can adaptively adjust its height and continue operating after detecting a positional deviation without stopping and resetting. This ensures both the safety of the rack and forks and the continuity and efficiency of the operation.

[0041] Furthermore, this invention also considers that if the forks directly impact the rack while extended at high speed, even with timely detection and adjustment, the massive inertial impact may still cause mechanical damage to the rack structure, fork electrodes, and even the stacker crane itself. Therefore, this invention further proposes a segmented speed control strategy: when the forks extend to a preset distance from the target storage location, the controller switches the forks from normal speed to low speed extension. During this low-speed phase, if the collision detection circuit detects contact between the conductor and the conductive strip, the aforementioned lifting adjustment action is immediately executed; if no closing signal is detected, it indicates that the fork tip height matches the storage location entrance, and the controller controls the forks to return to normal speed to complete the subsequent extension action, or maintains a low speed until the goods are fully delivered to the storage location. This preset distance can be set according to the fork extension stroke and rack structure, and is typically a safety buffer distance before the forks are fully extended. With this segmented speed control, even if there is a low position deviation at the front end of the fork, the contact with the conductive strip of the rack is flexible at low speed, which greatly reduces the impact force and effectively protects the mechanical integrity of the rack beam, fork electrodes and conductive strip, while avoiding the risk of electrode deformation or conductive strip detachment caused by high-speed impact.

[0042] Based on the above concept, the present invention provides a stacker crane, the stacker crane including: a first fork and a second fork arranged side by side, the first fork and the second fork having a detection surface located at the foremost end along their extension direction; Multiple conductive strips are respectively installed on the side wall of each layer of the shelf facing the forks, and the conductive strips extend along the length of the shelf; The collision detection circuit includes a first conductor and a second conductor, which cooperate with the conductive strip to form a contact switch; the first conductor is disposed on the detection surface of the first fork, and the second conductor is disposed on the detection surface of the second fork; A controller is used to control the lifting and extension of the first and second forks; the controller is communicatively connected to the collision detection circuit. When the first and second forks extend toward the shelf, causing the first and second conductors to simultaneously contact and become electrically connected with the conductive strip, the collision detection circuit closes and sends a closing signal to the controller. The controller then controls the first and second forks to rise until the closing signal disappears.

[0043] This solution utilizes mechanical contact to trigger a conductive circuit, exhibiting strong anti-interference capabilities and remaining unaffected by harsh working conditions such as dust and vibration. Furthermore, its simple structure and low cost allow for easy installation directly on existing stacker cranes, significantly enhancing the operational safety and reliability of automated storage and retrieval systems.

[0044] The stacker crane of the present invention will be described below with reference to the accompanying drawings and specific embodiments.

[0045] Please see Figures 2-12 This invention provides a stacker crane for use in automated warehousing systems, which works in conjunction with racks, rails and conveyor systems.

[0046] The automated warehousing system consists of multiple rack groups arranged side by side. Each rack group includes two sets of rack units 11 arranged opposite each other. The two sets of rack units 11 form an aisle for stacker crane operations. The ground rail 12 is laid in the middle of the ground in the aisle to provide horizontal movement guidance for the stacker crane.

[0047] Each shelving unit 11 includes several uprights 111 extending vertically, several first crossbars 112 extending horizontally, and several second crossbars 113 extending horizontally. The uprights 111, first crossbars 112, and second crossbars 113 are interconnected and enclose to form several arrayed storage locations, wherein the first crossbars 112 are used to support palletized goods.

[0048] The stacker of the present invention includes a traveling mechanism 20 that can move horizontally along a ground rail 12, a lifting mechanism 30 fixed on the traveling mechanism 20, a forklift mechanism 40 that can move up and down (i.e., move up and down) along the lifting mechanism 30, and a controller 70 that controls the operation of the traveling mechanism 20, the lifting mechanism 30, and the forklift mechanism 40.

[0049] The forklift mechanism 40 includes a loading platform 41, a first fork 42 and a second fork 43 arranged side by side, and a drive mechanism 44. Both the first fork 42 and the second fork 43 are telescopic forks, each having a fixed end connected to the loading platform 41 and a fork end that extends in the front-rear direction to pick up palletized goods. The fixed end is rotatably connected to the loading platform 41. Rotation of the fixed end relative to the loading platform 41 allows the first fork 42 and the second fork 43 to be aligned with the racking units on both sides of the aisle for picking or unloading operations.

[0050] The fork ends of the first fork 42 and the second fork 43 have upward-facing pressure-bearing surfaces for supporting cargo pallets, and forward-facing detection surfaces located at the foremost end of the fork end along its extension direction.

[0051] The stacker crane also includes a collision detection mechanism 50, which includes a plurality of conductive strips 51 and a collision detection circuit. The conductive strips 51 are disposed on the rack unit 11 and serve as the fixed detection end of the collision detection mechanism 50, while the collision detection circuit is disposed on the forks and serves as the movable detection end.

[0052] Specifically, each shelf unit 11 has a conductive strip 51 installed on the side wall of the second crossbar 113 below each shelf location facing the aisle. The conductive strip 51 extends along the length (i.e., left-right direction) of the shelf unit 11, covering all shelf locations on that layer, and the detection surface of the conductive strip 51 faces the aisle. The conductive strip 51 acts as a bridging conductor and is not connected to external wires; it is only used to provide an electrical connection path when the first conductor 52 and the second conductor 53 are in contact simultaneously.

[0053] The collision detection circuit is communicatively connected to the controller 70 and includes a first conductor 52 and a second conductor 53. The first conductor 52 and the second conductor 53, together with the conductive strip 51, form a normally open contact switch for the collision detection circuit. The first conductor 52 is disposed on the detection surface of the first fork 42, and the second conductor 53 is disposed on the detection surface of the second fork 43, with the detection surfaces of both conductors facing the shelf direction.

[0054] When the first fork 42 and the second fork 43 extend toward the target cargo position, if there is a height difference between the fork ends of the two forks, when the first conductor 52 and the second conductor 53 simultaneously abut against the conductive strip 51 below the target cargo position, the first conductor 52 and the second conductor 53 form an electrical connection through the conductive strip 51. The collision detection circuit switches from an open circuit state to a closed state and sends a closing signal to the controller 70. The controller 70 controls the lifting mechanism 30 to operate according to the closing signal, so that the first fork 42 and the second fork 43 are raised until the closing signal disappears.

[0055] The generation of this closed signal strictly depends on both conductors being in contact with the conductive strip, and it can only be triggered when the forks enter the rack area. This utilizes the physical spatial relationship between the rack and the forks as the detection condition, fundamentally avoiding false triggers caused by pallet offset or conveyor vibration. When the collision detection circuit is triggered, the controller 70 does not immediately stop the entire machine; instead, it drives the loading platform to adaptively raise to correct the positional deviation. Once the signal disappears, the storage and retrieval operations can continue. This process requires no manual intervention or machine shutdown reset, ensuring both the mechanical safety of the rack and forks and the continuity and efficiency of the automated warehouse's inbound and outbound operations.

[0056] Please see Figure 3 In one embodiment, an insulating structure 511 is provided between each conductive strip 51 and the second crossbar 113. The insulating structure is made of ceramic, epoxy resin or reinforced nylon to maintain electrical isolation between the conductive strip 51 and the second crossbar 113 and prevent the collision detection circuit from short-circuiting due to grounding of the metal frame of the shelf.

[0057] Please see Figure 3 In another embodiment, the insulation structure 511 of each conductive strip 51 is elastically connected to the corresponding second crossbar 113 by a number of buffer springs 54, so that the conductive strip can elastically yield and adaptively fit when it is abutted by the conductor of the fork. This absorbs the impact kinetic energy to avoid hard collision damage to the conductor, conductive strip and rack structure, and ensures that a stable and reliable electrical contact is formed between them through elastic reaction force, preventing poor contact or signal jitter caused by manufacturing and installation errors or slight shaking.

[0058] Preferably, the detection surface of the conductive strip 51 is a vertical plane; or, the contact surface between the conductive strip 51 and the conductor is an inclined or arc-shaped surface that slopes from top to bottom away from the second crossbar 113.

[0059] The height of the top of the conductive strip 51 is higher than the height of the corresponding second crossbar 113, so that the fork maintains a certain distance from the top of the first crossbar 112 after it extends into the storage position.

[0060] The conductive part of the conductive strip is made of any one of conductive silicone, copper foil, aluminum foil, or conductive film. Preferably, the conductive strip 51 is elastic, which can provide elastic buffer for the electrode and extend the service life of the electrode.

[0061] In existing technologies, the normal speed of the forklift mechanism 40 extending and retracting is typically high. During this process, if a collision occurs due to a positional deviation between the fork tip and the rack, the high-speed inertial impact of the fork tip on the rack will cause structural damage, mechanical vibration, and may even affect the palletized goods already stored on the rack. Therefore, this invention divides the extension action of the forklift mechanism 40 into a pre-detection stage of low-speed extension and a normal operation stage of normal-speed extension: Pre-detection phase: The forks extend from their initial position. Before the extension distance exceeds a preset distance S, the controller 70 controls the drive mechanism 44 to operate at a low speed, causing the first fork 42 and the second fork 43 to extend synchronously at a first speed v1, which is lower than the normal speed. During this phase, if the collision detection circuit triggers a closing signal, the controller 70 controls the first fork 42 and the second fork 43 to rise until the closing signal disappears; if no closing signal is triggered, the controller controls the first fork 42 and the second fork 43 to continue extending synchronously at the first speed v1.

[0062] Normal operation phase: When the closing signal triggered by the collision detection circuit disappears, or the collision detection circuit does not trigger the closing signal until the fork extension distance exceeds the preset distance S (i.e. the fork tip has entered the storage location entrance area), the controller 70 determines that the fork tip height matches the storage location entrance, controls the drive mechanism 44 to return to normal operating speed, so that the first fork 42 and the second fork 43 continue to extend synchronously at normal extension speed, quickly and efficiently delivering the goods into the storage location; or, according to the operation safety level requirements, the drive mechanism 44 maintains a low operating speed until the goods are completely delivered into the storage location.

[0063] The above-mentioned design reduces the inertial impact force when the fork tip comes into contact with the conductive strip 51 of the shelf due to deformation or positional deviation, so that the fork tip and the conductive strip form a flexible contact rather than a rigid collision. At the same time, the low extension speed provides sufficient time margin for the response of the collision detection circuit, the signal processing of the controller 70 and the start-up of the lifting mechanism 30, ensuring that the detection and lifting are completed in time before the fork actually hits the shelf structure.

[0064] Wherein, the preset distance S is greater than or equal to the distance between the initial position of the forks and the vertical plane where the entrance of the target storage location is located.

[0065] Depending on the shape of the detection surface of the conductive strip 51, the control of lifting the first fork 42 and the second fork 43 includes the following two implementation methods: In the first embodiment, when the collision detection circuit triggers a closing signal, the controller 70 controls the drive mechanism 44 to stop operating and simultaneously controls the lifting mechanism 30 to operate, causing the first fork 42 and the second fork 43 to stop extending and begin to lift, until the first conductor 52 and the second conductor 53 lose contact with the conductive strip 51, the collision detection circuit is disconnected, and the closing signal disappears; then the lifting mechanism 30 is controlled to stop operating, and the drive mechanism 44 returns to its normal operating speed, causing the first fork 42 and the second fork 43 to stop lifting and return to their normal extension speed to continue to extend synchronously.

[0066] In the second implementation, such as Figure 4As shown, the detection surface of the conductive strip 51 is an inclined or arc-shaped surface that slopes downwards away from the second crossbar 113, or the detection surface of the conductive strip 51 is a vertical plane and the conductive strip 51 is elastically connected to the second crossbar 113 by several buffer springs 54. When the collision detection circuit triggers a closing signal, the controller 70 controls the drive mechanism 44 and the lifting mechanism 30 to operate simultaneously, so that the first fork 42 and the second fork 43 continue to extend at a speed less than or equal to the first speed v1, and simultaneously begin to lift. The first fork 42 and the second fork 43 slide upwards along the detection surface while extending at a low speed, until the first conductor 52 and the second conductor 53 disengage from the conductive strip 51, the collision detection circuit is disconnected, and the closing signal disappears; then the lifting mechanism 30 is controlled to stop operating, the drive mechanism 44 returns to normal operating speed, so that the first fork 42 and the second fork 43 stop lifting and return to normal extension speed to continue to extend synchronously.

[0067] If the lifting height of the fork mechanism 40 reaches a preset threshold during the duration of the closing signal but the closing signal still does not disappear, it is determined that there are problems such as conductor jamming or circuit failure. The lifting mechanism 30 and the drive mechanism 44 are controlled to stop operating and an alarm is issued, waiting for manual inspection.

[0068] Furthermore, considering that palletized goods in the same batch of goods entering the warehouse usually have similar specifications and consistent weight distribution, and that the downward elastic deformation of the fork tip due to the weight of the goods has statistical consistency within the same batch, the controller 70 is equipped with a self-learning compensation program to reduce the frequency of collision detection triggering in subsequent operations within the same batch and improve operational efficiency. During the storage and retrieval operation of the current palletized goods, if the collision detection circuit triggers a closing signal and the signal disappears after the lifting adjustment action, the controller 70 records the actual lifting height Δh of the forklift mechanism 40 from the generation of the closing signal to the disappearance of the signal during this operation, and temporarily stores this lifting height Δh as the empirical correction value for this batch of goods. In the storage and retrieval operation of the next palletized goods from the same batch, before controlling the forks to extend towards the target storage location, the controller 70 first controls the lifting mechanism 30 to drive the forklift mechanism 40 to slightly raise the empirical correction value Δh, so that the fork tip is pre-raised to the compensation height before performing the extension action. This pre-compensation operation makes the fork tip closer to the theoretical height of the storage location entrance, thereby reducing or avoiding the triggering of the collision detection circuit.

[0069] The collision detection circuit maintains real-time monitoring during the extension process after pre-compensation. If the front end of the fork still has a low-position deviation due to deviation in the actual weight of the goods, shelf installation error, or wear and tear of the fork structure, the collision detection circuit can still be closed and triggered, and the controller 70 will perform the aforementioned lifting and adjustment action to ensure that the system safety is not reduced due to pre-compensation.

[0070] The experience correction value Δh is reset to zero after all storage and retrieval operations for the same batch of palletized goods are completed. The controller 70 is configured with a batch identification mechanism to determine whether the current operation belongs to a new batch. For example, the batch identification mechanism includes: the controller 70 communicates with the control system of the automated warehousing system to obtain the goods code or batch number of the current operation; when the goods code / batch number of the current operation is inconsistent with the previous operation, it is determined that the previous batch of operations has been completed, the experience correction value Δh is automatically reset to zero, and the value is relearned and recorded in the next operation.

[0071] In this embodiment, the collision detection circuit includes the following two implementation methods: Please see Figure 5 In the first embodiment, the collision detection circuit includes a power supply V, an optocoupler OP, and a current-limiting resistor R. A first conductor 52 is electrically connected to the positive terminal of the power supply V, a second conductor 53 is electrically connected to the anode of the input terminal of the optocoupler OP, and the cathode of the input terminal of the optocoupler OP is connected to the negative terminal of the power supply V via the current-limiting resistor R1, forming a front-end detection circuit. The collector of the output terminal of the optocoupler OP is connected to the power supply VCC via a pull-up resistor R2, and this collector is electrically connected to the input port Vout of the controller 70. The emitter of the output terminal of the optocoupler OP is connected to the ground terminal GND. The controller 70 is electrically connected to the walking mechanism 20, the lifting mechanism 30, and the forking mechanism 40, and can control the operation of the walking mechanism 20, the lifting mechanism 30, and the forking mechanism 40. When the first conductor 52 and the second conductor 53 come into contact with the conductive strip 51 on the shelf, the conductive strip 51 turns on the normally open contact switch between the first conductor 52 and the second conductor 53. The current flows through the current-limiting resistor and through the LED at the input of the optocoupler to make it light up. The phototransistor at the output of the optocoupler then turns on, and the controller 70 detects the closed signal.

[0072] The resistance value of the current-limiting resistor is configured such that when the first conductor 52 and the second conductor 53 are short-circuited through the conductive strip 51, the circuit current is not greater than the maximum allowable operating current of the optocoupler LED.

[0073] Please see Figure 6In the second embodiment, a connecting rod is provided between the front ends of the first fork 42 and the second fork 43. A power supply V, a current-limiting resistor R1, a voltage regulator module VR, and a wireless transmitter TX are mounted on the connecting rod. The controller 70 is equipped with a wireless receiver. The first conductor 52 is electrically connected to the positive terminal of the power supply V through the current-limiting resistor R1. The second conductor 53 is electrically connected to the positive input terminal of the voltage regulator module VR, and the negative input terminal of the voltage regulator module VR is electrically connected to the negative terminal of the power supply V. The power supply terminal of the wireless transmitter TX is electrically connected to the output terminal of the voltage regulator module VR; that is, the positive output terminal of the voltage regulator module VR is connected to the positive power supply terminal of the wireless transmitter TX, and the negative power supply terminal of the wireless transmitter TX is connected to the negative output terminal of the voltage regulator module VR. When the first conductor 52 and the second conductor 53 are connected, current flows into the voltage regulator module VR through the current-limiting resistor. The voltage regulator module VR converts the input voltage into a stable operating voltage required by the wireless transmitter TX and supplies it to the wireless transmitter. After being powered on, the wireless transmitter TX starts and sends a closing signal to the wireless receiver. Compared to collision detection circuits that use optocouplers, this solution requires minimal modification to the forks, is simple to implement, and has a lower cost, making it suitable for large-scale application in existing automated storage and retrieval systems.

[0074] An energy storage capacitor and a transient suppression diode are connected in parallel between the positive and negative input terminals of the voltage regulator module. The energy storage capacitor is used to maintain the stability of the input voltage of the voltage regulator module when the electrode contacts bounce, and the transient suppression diode is used to absorb the induced voltage spikes generated when the electrodes are disconnected.

[0075] The wireless transmitter is a low-power standby type wireless transmitter with an integrated fast start-up circuit. After being powered on, it can complete initialization and send a closing signal within a preset time.

[0076] Please see Figures 7-9 In one embodiment, the collision detection mechanism 50 includes a first protective sleeve sleeved around the periphery of the first conductor 52 and capable of axial extension and retraction, and a second protective sleeve sleeved around the periphery of the second conductor 53 and capable of axial extension and retraction. When the first fork 42 and the second fork 43 extend and abut against the conductive strip 51, the first protective sleeve is compressed under pressure, exposing the top end of the first conductor 52, and the second protective sleeve is compressed under pressure, exposing the top end of the second conductor 53. The first conductor 52 and the second conductor 53 are electrically connected to the conductive strip 51. When the first fork 42 and the second fork 43 separate from the conductive strip 51, the pressure disappears, the first protective sleeve resets and wraps around the first conductor 52, and the second protective sleeve resets and wraps around the second conductor 53.

[0077] The first protective sleeve and the second protective sleeve are made of insulating material.

[0078] Specifically, both the first and second protective sleeves are telescopic cylinders 55. Each telescopic cylinder 55 includes an inner cylinder 551 and an outer cylinder 552. The end of the inner cylinder 551 facing the corresponding fork is fixedly connected to the detection surface of the corresponding fork. The outer cylinder 552 is sleeved on the outer periphery of the inner cylinder 551 and slides in cooperation with the inner cylinder 551. A through hole 553 is formed on the end wall of the outer cylinder 552 away from the corresponding fork, allowing the corresponding conductor to extend out. The outer cylinder 552 is elastically connected to the detection surface of the corresponding fork by a spring 554. In its natural state, a first distance is maintained between the outer end face of the outer cylinder 552 and the top of the corresponding conductor. The telescopic cylinder 55 has a maximum compression amount, which is greater than the first distance, to ensure that when the outer cylinder 552 is compressed and retracted, the corresponding conductor can protrude from the through hole 553 and contact the conductive strip.

[0079] Preferably, the first conductor 52 and the second conductor 53 are electrode posts that can elastically extend and retract along the axial direction. In their natural state, the front end face of the protective sleeve protrudes from the top of the corresponding electrode post. The protective sleeve has a maximum axial compression, which is greater than the distance between the top of the electrode post and the front end face of the protective sleeve. This arrangement ensures that after the front end of the telescopic cylinder 55 touches the conductive strip 51, the outer cylinder 552 first slides inward relative to the inner cylinder 551 and retracts; when the retraction of the outer cylinder 552 reaches the first distance, the top of the conductor protrudes from the through hole 553 and abuts against the conductive strip 51; if the fork continues to extend, causing further pressure on the outer cylinder, the conductor itself elastically retracts along the axial direction, forming a secondary buffer. This structure avoids rigid compression between the conductor and the conductive strip, preventing the conductor from undergoing plastic deformation or damage due to excessive pressure, and utilizes the rebound force of the conductor itself to maintain reliable contact pressure between the conductor and the conductive strip, ensuring stable conduction of the circuit signal.

[0080] Please see Figure 10In another embodiment, a columnar electrode 555 is fixedly installed at the through hole 553 of the outer cylinder 552. One end of the columnar electrode 555 is exposed on the outer end face of the outer cylinder 552 as a contact front end, and the other end extends into the interior of the outer cylinder 552 and is provided with an insulating limiting part. The insulating limiting part is elastically connected to the detection surface of the corresponding fork through a spring 554. The conductor corresponding to the telescopic cylinder 55 is fixed inside the inner cylinder 551 and is located on the axial retraction path of the columnar electrode 555. In the natural state, the columnar electrode 555 and the conductor maintain an axial distance; when the front end of the telescopic cylinder 55 touches the conductive strip 51 and is compressed and retracted, the columnar electrode 555 retracts synchronously with the outer cylinder 552, and its column is electrically connected to the conductor, thereby turning on the collision detection circuit. If the forks continue to extend, causing further pressure on the outer cylinder 552, the spring 554 will further compress, causing the outer cylinder 552 to continue sliding inward relative to the inner cylinder 551, while the column of the column electrode 555 remains in sliding electrical contact with the conductor.

[0081] See Figures 11-13 The drive mechanism 44 includes a drive motor 441, a drive wheel 442 coaxially fixed to the output end of the drive motor 441, and at least one first transmission wheel 443 meshing with the drive wheel 442. Each first transmission wheel 443 is coaxially fixed to a second transmission wheel 445 via a transmission rod 444. The first transmission wheel 443 meshes with the fork end of the first fork 42, and the second transmission wheel 445 meshes with the fork end of the second fork 43. The rotation of the first transmission wheel 443 and the second transmission wheel 445 drives the fork ends of the first fork 42 and the second fork 43 to extend or retract synchronously.

[0082] The fixed end of the first fork 42 is a fixed frame 421 mounted on the loading platform 41, and the fork end includes a middle fork 422 slidably connected to the fixed frame 421. The middle fork 422 includes a base plate 4221 and a first rack 4222 disposed below the base plate 4221, the first rack 4222 meshing with a first drive wheel 443 for transmission.

[0083] To extend the length of the first fork 42 after it extends, the fork end also includes an upper fork 423 slidably connected to the middle fork 422. The upper fork 423 includes a top plate 4231 and side plates 4232 extending downwards from the left and right edges of the top plate 4231. A second rack 4233 is provided at the bottom of the top plate 4231, and a third rack 4211 is provided at the top of the fixing frame 421. The middle fork 422 includes at least one gear 4223, which penetrates the bottom plate 4221. The gear 4223 is rotatably connected to the bottom plate 4221 at its center, meshes with the second rack 4233 at its top, and meshes with the third rack 4211 at its bottom, so that the movement of the middle fork 422 can drive the movement of the upper fork 423.

[0084] The first conductor 52 is disposed at the end of the upper fork 423 of the first fork 42, and the second conductor 53 is disposed at the end of the upper fork of the second fork 43.

[0085] To improve the stability of the fork extension and retraction, the middle fork 422 is provided with a first groove 4224 opening inward and a second groove 4225 opening outward on both the left and right sides. The fixing frame 421 is provided with a first sliding structure 4212 on both the left and right sides, which slides in conjunction with the first grooves 4224 on the left and right sides of the middle fork 422, respectively. The upper fork 423 is provided with a second sliding structure 4234 on both the left and right sides, which slides in conjunction with the second grooves 4225 on the left and right sides of the middle fork 422, respectively.

[0086] Furthermore, the bottom of the base plate 4221 of the fork 422 is provided with a left side plate and a right side plate. Both the left side plate and the right side plate are "⊥" shaped and are composed of a vertical plate and a horizontal plate. The left side plate and the base plate 4221 form the first groove and the second groove located on the left side of the fixing frame, and the right side plate and the base plate 4221 form the first groove and the second groove located on the right side of the fixing frame.

[0087] The left side plate has a conductive area 4226 on its vertical plate, which extends in the front-to-back direction and is exposed on the left and right sides of the vertical plate. The first sliding structure 4212 on the left side of the fixing frame 421 has a fixing frame conductive spring 4213, which is an arc-shaped copper piece protruding towards the vertical plate. The arc-shaped copper piece slides against the conductive area 4226 on the vertical plate.

[0088] The second sliding structure 4234 on the left side of the upper fork 423 is provided with an upper fork conductive spring 4235. The upper fork conductive spring 4235 is connected to the first conductor 52 through a wire. The upper fork conductive spring 4235 is an arc-shaped copper piece protruding towards the vertical plate. The arc-shaped copper piece slides and abuts against the conductive area 4226 on the vertical plate, thereby achieving electrical connection with the fixed frame conductive spring 4213 through the conductive area 4226.

[0089] Preferably, the fixed frame conductive spring 4213 is located at the end of the fixed frame 421 near the fork end, and the upper fork conductive spring 4235 is located at the end of the upper fork 423 near the fixed end.

[0090] The first rack 4222 is located at the bottom of the horizontal plate of the right side plate of the middle fork 422.

[0091] The second fork 43 is provided with a conductive spring structure symmetrical to the first fork 42, including a fixed frame conductive spring on the fixed frame and an upper fork conductive spring on the upper fork. The upper fork conductive spring is electrically connected to the second conductor 53 and is electrically connected to the fixed frame conductive spring through the conductive area 4226 on the middle fork.

[0092] The conductive spring 4213 of the fixed frame on the first fork 42 is electrically connected to the positive terminal of the power supply via a wire. The conductive spring 4213 of the fixed frame on the second fork is electrically connected to the anode of the optocoupler input terminal via a wire. The cathode of the optocoupler input terminal is connected to the negative terminal of the power supply via a current-limiting resistor, thus forming the front-end detection circuit.

[0093] The structure of the second fork 43 is basically the same as that of the first fork 42, and will not be described in detail again.

[0094] For further details, please refer to Figure 11 The first sliding structures 4212 on the left and right sides of the fixing frame are each equipped with a first pulley, which is located in the corresponding first groove 4224 and slidably connected to the bottom of the base plate 4221 and the top of the horizontal plate. The second sliding structures 4234 on the left and right sides of the upper fork are each equipped with a second pulley, which is located in the corresponding second groove 4225 and slidably connected to the bottom of the base plate 4221 and the top of the horizontal plate. The use of first and second pulleys improves the stability of the fork extension and retraction.

[0095] like Figure 14 As shown, the walking mechanism 20 includes a base 21, and walking wheels 22 and a walking motor 23 mounted on the base 21. The walking wheels 22 are driven by the walking motor 23 to walk along the top surface of the ground rail 12. Guide wheels 24 are distributed on both sides below the walking wheels 22, which walk along the side of the ground rail 12.

[0096] The lifting mechanism 30 includes a column 31 fixedly installed on the base 21. The column 31 is provided with a slide rail, and the fork-lifting mechanism is provided with a pulley that cooperates with the slide rail. The fork-lifting mechanism is slidably connected to the column 31 through the slide rail and the pulley.

[0097] The top of the column 31 is provided with a top plate 32, and the base 21 is also provided with a lead screw 33. The bottom end of the lead screw 33 is rotatably connected to the top of the base 21 via a bearing, and the top end is rotatably connected to the top plate 32 via a bearing. A servo motor 34 is installed on one side of the top plate 32. Both the top of the servo motor 34 and the lead screw 33 are fitted with pulleys, and a synchronous belt is fitted on the outer side of the pulleys. The servo motor 34 can drive the lead screw 33 to rotate through the synchronous belt and the pulleys. The outer side of the lead screw 33 is threadedly engaged with the lead screw nut of the forklift mechanism. The rotation of the lead screw 33 can drive the forklift mechanism to move up and down.

[0098] like Figure 2 As shown, the stacker crane also includes a top rail 60, and the top of the lifting mechanism 30 cooperates with the top rail and can move along the top rail 60. Specifically, the top of the lifting mechanism is provided with multiple pairs of limiting rollers, and two of the limiting rollers in each pair are respectively arranged on both sides of the top rail and can roll along the top rail.

[0099] Compared with the prior art, the present invention has the following advantages: (1) By fixing the conductive strip to the crossbar of the shelf and distributing the conductors at the front end of the double forks, the present invention strictly limits the triggering of collision detection to the specific spatial condition that the double forks enter the shelf area at the same time; the forks will not contact the conductive strip of the shelf when picking up and putting down the pallet in the conveying system, thus fundamentally avoiding false triggering caused by pallet offset or conveying vibration.

[0100] (2) This invention divides the fork extension into a pre-operation low-speed detection stage and a normal operation stage. The initial extension section, where interference is most likely to occur, operates at low speed to ensure that any collision is a flexible contact rather than a rigid impact. When the collision detection circuit is triggered, the controller does not immediately stop the entire machine; instead, it drives the loading platform to adaptively raise to correct the positional deviation. Once the signal is confirmed to have disappeared, the storage and retrieval operations can continue. This process requires no manual intervention or machine shutdown / reset, ensuring both the mechanical safety of the racks and forks and the continuity and efficiency of the automated warehouse's inbound and outbound operations.

[0101] (3) The collision detection mechanism of the present invention mainly consists of conductive strips, conductive bodies, protective sleeves, and simple circuits, without the need for additional high-precision laser rangefinders, vision sensors, or complex data processing units. This solution has low hardware costs, is easy to install and debug, and has excellent engineering economy and applicability.

[0102] (4) The controller of the present invention is equipped with a self-learning compensation program. By recording the actual lifting correction value caused by the elastic deformation of the forks during the operation of the same batch of goods, the height pre-compensation is performed before the next item of the same batch of goods is stored or retrieved, so that the front end of the forks is closer to the theoretical height of the loading position entrance, thereby reducing or avoiding the frequency of collision detection.

[0103] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A stacker crane, comprising a first fork and a second fork arranged side by side, the first fork and the second fork having a detection surface located at the foremost end along their extension direction, characterized in that, Also includes: Multiple conductive strips are respectively installed on the side wall of each layer of the shelf facing the forks, and the conductive strips extend along the length of the shelf; The collision detection circuit includes a first conductor and a second conductor, wherein the first conductor, the second conductor, and the conductive strip cooperate to form a contact switch; The first conductor is disposed on the detection surface of the first fork, and the second conductor is disposed on the detection surface of the second fork; when the first fork and the second fork extend toward the shelf, and the first conductor and the second conductor simultaneously contact and are electrically connected with the conductive strip, the collision detection circuit closes and issues an alarm.

2. The stacker crane according to claim 1, characterized in that, It also includes a controller for controlling the lifting and extension of the first and second forks; the controller is communicatively connected to the collision detection circuit, and when the collision detection circuit is closed, it sends a closing signal to the controller, which then controls the first and second forks to lift upwards until the closing signal disappears.

3. The stacker crane according to claim 2, characterized in that, When the first and second forks extend toward the target storage location on the shelf, the controller controls the first and second forks to extend synchronously at a first speed; If a closing signal is received from the collision detection circuit, the first and second forks are controlled to rise until the closing signal disappears. Then, the first and second forks are controlled to stop rising and resume normal extension speed to continue extending. If no closing signal is received from the collision detection circuit, the first and second forks are controlled to continue extending at a first speed until their extension distance is greater than a preset distance. Then, the first and second forks are controlled to return to the normal extension speed and continue extending. The preset distance is greater than or equal to the distance between the initial position of the forks and the vertical plane where the entrance of the target cargo position is located, and the first speed is less than the normal extension speed.

4. The stacker crane according to claim 3, characterized in that, If the controller receives a closed signal from the collision detection circuit during the extension of the first and second forks toward the shelf, it will control the first and second forks to stop extending and start lifting until the closed signal disappears. Then, it will control the first and second forks to stop lifting and resume normal extension speed to continue extending synchronously.

5. The stacker crane according to claim 3, characterized in that, The detection surface of the conductive strip is an inclined or curved surface that slopes downwards away from the crossbar, or the detection surface of the conductive strip is a vertical plane and the conductive strip is elastically connected to the crossbar by several buffer springs; if the controller receives a closed signal from the collision detection circuit during the extension of the first and second forks toward the shelf, it controls the first and second forks to continue extending at a speed less than or equal to the first speed, and simultaneously begins to lift, until the closed signal disappears, and then controls the first and second forks to stop lifting and resume to the normal extension speed to continue to extend synchronously.

6. The stacker crane according to claim 2, characterized in that, If the lifting height of the first and second forks reaches a preset threshold during the duration of the closing signal and the closing signal has not disappeared, the controller will stop the first and second forks from moving and issue an alarm.

7. The stacker crane according to claim 1, characterized in that, The first conductor and the second conductor are respectively provided with axially expandable protective sleeves. When the protective sleeves are compressed under pressure, the corresponding conductors are exposed. After the pressure is removed, the protective sleeves are reset and wrap around the corresponding conductors.

8. The stacker crane according to claim 7, characterized in that, The first and second conductors are electrode posts that can elastically expand and contract along the axial direction; in their natural state, the front end face of the protective sleeve protrudes from the top of the corresponding electrode post; the protective sleeve has a maximum axial compression amount, which is greater than the distance between the top of the electrode post and the front end face of the protective sleeve.

9. The stacker crane according to claim 2, characterized in that, The drive mechanism includes a drive motor and a first transmission wheel and a second transmission wheel that are connected to the drive motor. The first fork and the second fork each include a fixed frame, a middle fork that is slidably connected to the fixed frame, and an upper fork that is slidably connected to the middle fork. Each middle fork has a first rack extending along its length at its bottom, and at least one gear is rotatably connected to each middle fork. The first rack of the first fork meshes with the first transmission wheel for transmission, and the first rack of the second fork meshes with the second transmission wheel for transmission. Each upper fork has a second rack extending along its length for transmission, and the second rack meshes with the gear of the corresponding middle fork for transmission.

10. The stacker crane according to claim 9, characterized in that, Each middle fork has a conductive area extending along its length; each fixed frame has a fixed frame conductive spring that is electrically connected to the collision detection circuit, and the fixed frame conductive spring slides against the conductive area of ​​the corresponding middle fork; each upper fork has an upper fork conductive spring that slides against the conductive area of ​​the corresponding middle fork; the first conductor and the second conductor are respectively located at the upper fork end of the corresponding fork and are electrically connected to the corresponding upper fork conductive spring.

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