A scissor arm carrying docking device for AGV

Abstract

The utility model discloses a kind of scissor arm carrying butt joint devices for AGV dolly.The utility model includes the top plate being set on the AGV dolly top, the both sides of top plate are equipped with power part, the output end of power part is equipped with lifting part, lifting part includes the scissor arm lifting rod being set in the output end of power part, scissor arm lifting rod top is equipped with lifting plate, lifting plate top surface is equipped with V-shaped limiting block for supporting material;The top plate is also equipped with the control panel connected with power part.The utility model effectively expands the lifting range by lifting part, and expands the applicable scenario of device.

Description

Technical Field

[0001] This utility model relates to a handling and docking device, and more particularly to a scissor arm handling and docking device for AGV trolleys. Background Technology

[0002] In industrial production fields such as printing and coating, the handling and equipment docking of materials (such as roll paper and coating substrates) are crucial for ensuring the continuous operation of the production line. In traditional production models, this process relies heavily on manual labor in conjunction with forklifts and overhead cranes. However, this method suffers from low positioning accuracy and requires repeated adjustments, leading to low docking efficiency. Furthermore, manual handling of rolls at high workstations such as printing and coating machines often requires the use of forklifts or overhead cranes for hoisting and adjusting height and horizontal position under manual guidance. This process is not only cumbersome but also limited by human precision, prone to material misalignment, docking errors, and even safety risks due to material movement at high workstations. With the development of automation technology, AGVs (Automated Guided Vehicles) are increasingly being used in material handling scenarios. However, their conventionally designed platform height is fixed, only suitable for workstations of specific heights, and cannot meet the needs of high workstations in printing and coating production lines. Chinese invention patent CN108482521A discloses a docking mechanism for AGV (Automated Guided Vehicle) carts transporting racks, specifically including a traction structure, a traction lifting component, a lifting structure, and a lifting component. The traction structure is used for traction and transport of the racks by the AGV carts, and the lifting structure is used for lifting and transporting the racks by the AGV carts. The traction structure includes a traction component and a sleeve that cooperates with the traction component; the traction component and the sleeve can move relative to each other and are sleeved. The traction lifting component is connected to the traction component or the sleeve. The lifting structure includes a docking component; the lifting component and the docking component can move relative to each other and lift the docking component. The traction lifting component and the lifting component can be selectively connected. The traction lifting component or the lifting component is connected to the AGV cart. However, this type of docking mechanism also has areas for improvement: for example, the lifting height of this type of docking mechanism is limited, and additional assistance is required when rolling up and down in high-workstation applications, making it inconvenient to use. Summary of the Invention

[0003] The purpose of this invention is to provide a scissor lift handling and docking device for AGV (Automated Guided Vehicle) trolleys. This invention effectively expands the lifting range and broadens the applicable scenarios of the device through its lifting mechanism.

[0004] The technical solution of this utility model is as follows: A scissor arm handling and docking device for AGV trolleys includes a top plate set above the AGV trolley, power units are provided on both sides of the top plate, and a lifting unit is provided at the output end of the power unit. The lifting unit includes a scissor arm lifting rod set at the output end of the power unit, a lifting plate is provided at the top of the scissor arm lifting rod, and a V-shaped limiting block for supporting materials is provided on the top surface of the lifting plate; a control plate connected to the power unit is also provided on the top plate.

[0005] In the aforementioned AGV scissor arm handling and docking device, the power unit includes a motor fixed to the top surface of the top plate, the output end of the motor is connected to a transmission mechanism, and the output end of the transmission mechanism is connected to the lower movable end of the scissor arm lifting rod; the lifting plate is provided with an upper sliding group, and the upper movable end of the scissor arm lifting rod is connected to the upper sliding group.

[0006] In the aforementioned AGV scissor arm handling and docking device, the transmission mechanism includes a lead screw connected to the output end of a motor. The two ends of the lead screw are provided with first bearing seats fixed on the top plate. A lead screw slider is sleeved on the lead screw and inside the first bearing seats. The lower movable end of the scissor arm lifting rod is set on the lead screw slider.

[0007] In the aforementioned AGV scissor arm handling and docking device, the lead screw slider is fitted with a connecting layer, connecting rods are fixed on both sides of the connecting layer, and a first movable slider is fixed at the end of the connecting rod.

[0008] In the aforementioned AGV scissor arm handling and docking device, a first slide rail is provided on the top surface of the top plate and below the first movable slider. The first slide rail is engaged with the first movable slider and the first movable slider slides within the first slide rail.

[0009] In the aforementioned AGV scissor arm handling and docking device, a second bearing seat is fixed on the top surface of the top plate and on both sides of the motor.

[0010] In the aforementioned AGV scissor lift handling and docking device, the scissor lift includes a first inclined rod and a second inclined rod, which are centrally intersecting and hinged at the intersection. The bottom end of the first inclined rod is hinged to a connecting rod, serving as the lower movable end of the scissor lift. A third bearing seat is fixed on the bottom surface of the lifting plate and above the second bearing seat, and the third bearing seat is hinged to the top end of the first inclined rod, serving as the upper fixed end of the scissor lift. The bottom end of the second inclined rod is hinged to the second bearing seat, serving as the lower fixed end of the scissor lift. The top end of the second inclined rod is connected to an upper sliding assembly, serving as the upper movable end of the scissor lift.

[0011] In the aforementioned AGV scissor arm handling and docking device, the upper sliding group includes a second slide rail disposed on the bottom surface of the lifting plate and at a corresponding position above the first slide rail. A second movable slider is fitted inside the second slide rail, and the second movable slider slides inside the second slide rail. The second movable slider is hinged to the top end of the second inclined rod.

[0012] In the aforementioned AGV scissor arm handling and docking device, the motor output end is connected to a coupling, and the motor output end is connected to the transmission mechanism through the coupling.

[0013] In the aforementioned AGV scissor arm handling and docking device, the V-shaped limiting block includes two symmetrical blocks that tilt towards the middle, forming a limiting groove between the symmetrical blocks, and the symmetrical blocks are fixed to the lifting plate.

[0014] Compared with the prior art, the present invention has the following advantages: 1. This utility model includes a lifting unit, with scissor arm lifting rods on both sides and a lifting plate at the top of the scissor arm lifting rods. Through the structural combination of the scissor arm lifting rods on both sides and the top lifting plate, this utility model effectively expands the maximum lifting range of the device, breaking the limitation of traditional AGV handling devices that are only suitable for ordinary or low working positions. It not only meets the needs of conventional work scenarios but can also be adapted to the up-and-down winding operations of high-working-position equipment such as printing machines and coating machines, expanding the applicable scenarios of the device and reducing the cost for enterprises to purchase dedicated devices for equipment of different heights. Furthermore, this utility model can optimize high-working-position operation processes, eliminating the need for additional auxiliary equipment such as forklifts and overhead cranes. Through the precise movement of the AGV trolley and the flexible adjustment of the lifting unit height, materials can be directly delivered to the target docking height, shortening the time for a single up-and-down winding operation, avoiding idling of the production line due to low docking efficiency, and ensuring continuous production of printing, coating, and other production lines.

[0015] 2. The transmission mechanism of this utility model, through the transmission structure composed of a lead screw and a lead screw slider, can accurately convert the rotational motion of the motor into the linear motion of the lead screw slider, and then transmit it to the lifting part through the connecting rod. This ensures that the height adjustment of the scissor arm lifting rod and the lifting plate strictly follows the preset trajectory and speed, effectively avoiding lifting deviation or swaying. It accurately adapts to the precision requirements of high-level docking of printing machines, coating machines, etc., and reduces material loss and equipment downtime caused by docking deviation.

[0016] 3. The scissor lift of this utility model adopts a centrally cross-shaped design with hinges at the intersection. This cross-hinged structure transforms the lifting action into the opening and closing motion of the two inclined rods. Compared to a single telescopic rod or a single-sided support structure, the lifting stroke can be flexibly changed by adjusting the opening and closing angle of the inclined rods, easily achieving a wide range of height adjustments. This not only meets the needs of low-level material storage but also adapts to high-level rolling operations such as printing machines and coating machines, significantly improving the device's adaptability to different working scenarios. Simultaneously, the cross-shaped layout creates a symmetrical triangular stable support structure for the scissor lift, evenly distributing the weight to the two inclined rods and the bottom connection point when carrying materials, avoiding tilting of the lifting plate caused by concentrated force on one side. Furthermore, the hinge points can rotate flexibly, ensuring synchronous and smooth movement of the inclined rods during lifting.

[0017] 4. In this invention, the first slide rail on the top plate and the first movable slider are mutually engaged, providing a fixed movement path for the first movable slider and restricting it to slide only along the slide rail direction, effectively preventing slider deviation. This design ensures that the trajectory of the lead screw slider driving the first movable slider through the connecting rod is regular, thereby ensuring synchronous and stable movement of the scissor lift.

[0018] 5. This utility model includes a V-shaped limiting block, which comprises two symmetrical blocks inclined towards the center, forming a limiting groove between the symmetrical blocks. The symmetrical blocks are fixed to the lifting plate. The inwardly inclined symmetrical block design makes the entrance of the limiting groove flare outward, which can play a certain guiding role when the material enters the limiting groove. Even if there is a slight deviation in the initial position of the component, it can smoothly enter the groove through the guidance of the inclined surface, effectively limiting the material placed on the lifting plate and preventing the material from shifting during the movement or lifting of the AGV, ensuring the safety of the material handling process. It is especially suitable for scenarios with high requirements for material stability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the highest-level structure of the main view (including the AGV trolley) of this utility model; Figure 2 This is a schematic diagram of the highest structural position of the main view (excluding the AGV trolley) of this utility model; Figure 3 This is a schematic diagram of the lowest structural position of the main view (excluding the AGV trolley) of this utility model; Figure 4 This is a side view of the structure of this utility model; Figure 5 This is a top view of the structure of this utility model; Figure 6 This is a partially enlarged top view of the present invention; Figure 7 This is a structural diagram of the V-shaped limiting block.

[0020] The labels in the attached diagram are as follows: 1-Top plate, 2-Power unit, 21-Motor, 211-Coupling, 22-Transmission mechanism, 23-Lead screw, 24-First bearing seat, 25-Lead screw slider, 26-Connecting layer, 27-Connecting rod, 28-First moving slider, 29-First slide rail, 3-Lifting unit, 31-Scissor arm lifting rod, 32-Lifting plate, 321-Upper sliding assembly, 33-V-shaped limiting block, 331-Symmetrical block, 332-Limiting groove, 34-First inclined rod, 35-Second inclined rod, 36-Second bearing seat, 37-Third bearing seat, 38-Second slide rail, 39-Second moving slider, 5-Control panel. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0022] Example: A scissor lift handling and docking device for AGV (Automated Guided Vehicle) trolleys, configured as follows: Figure 1-7As shown, the device includes a top plate 1 mounted above the AGV trolley, power units 2 on both sides of the top plate 1, and a lifting unit 3 at the output end of the power units 2. The lifting unit 3 includes a scissor arm lifting rod 31 mounted at the output end of the power units 2, and a lifting plate 32 at the top of the scissor arm lifting rod 31. An upper sliding assembly 321 is mounted on the lifting plate 32. This invention, through the structural combination of the scissor arm lifting rods 31 on both sides and the top lifting plate 32, effectively expands the maximum lifting range of the device, breaking the limitation of traditional AGV handling devices that are only suitable for ordinary or low working positions. It not only meets the needs of conventional work scenarios but can also be adapted to the up-and-down rolling operations of high-working-position equipment such as printing machines and coating machines, expanding the applicable scenarios of the device and reducing the cost for enterprises to purchase dedicated devices for equipment of different heights. Furthermore, this invention optimizes the high-position operation process, eliminating the need for additional auxiliary equipment such as forklifts and overhead cranes. Through the precise movement of the AGV trolley and the flexible adjustment of the lifting unit height, materials can be directly delivered to the target docking height, shortening the time for a single roll-up / roll-down operation, preventing the production line from idling due to low docking efficiency, and ensuring continuous production in printing, coating, and other production lines. The scissor lift arm 31 includes a first inclined rod 34 and a second inclined rod 35, which are centrally intersecting and hinged at the intersection. The cross-hinged structure transforms the lifting motion into the opening and closing motion of the two diagonal bars. Compared to a single telescopic bar or a single-sided support structure, the lifting stroke can be flexibly changed by adjusting the opening and closing angle of the diagonal bars, easily achieving a wide range of height adjustments. This not only meets the needs of material storage at low workstations but also adapts to high-workstation up-and-down rolling operations such as printing machines and coating machines, significantly improving the device's adaptability to different work scenarios at different heights. At the same time, the cross-shaped layout makes the scissor arm lifting rod 31 form a symmetrical triangular stable support structure. When carrying materials, it can evenly distribute the weight to the two diagonal bars and the bottom connection point, avoiding the tilting of the lifting plate 32 caused by concentrated force on one side. Moreover, the hinge point can rotate flexibly, ensuring that the movement of the diagonal bars is synchronous and smooth during the lifting process, effectively reducing jamming or shaking, ensuring the stability of materials during the lifting process, and reducing the safety risk of materials slipping during high-workstation operations. Furthermore, this structure eliminates the need for complex multi-segment telescopic components, resulting in fewer overall parts and a simpler connection method. This not only reduces manufacturing costs but also facilitates individual maintenance and replacement after wear at the hinge points, minimizing the difficulty and cost of subsequent equipment maintenance. Simultaneously, the compact, cross-design saves installation space on the AGV trolley, avoiding layout conflicts with other components and improving the overall space utilization. The top of the lifting plate 32 is equipped with a V-shaped limiting block 33 for supporting materials. The V-shaped limiting block 33 includes two symmetrical blocks 331 inclined inwards, forming a limiting groove 332 between the symmetrical blocks 331. The symmetrical blocks 331 are fixed to the lifting plate 32. The inwardly inclined design of the symmetrical blocks 331 causes the entrance to the limiting groove 332 to expand outwards, providing a guiding effect when materials enter the limiting groove 332.Even with slight initial positional deviations, the inclined surface guides the material smoothly into the trough, effectively limiting the movement of materials placed on the lifting plate 32 and preventing displacement during AGV movement or lifting. This ensures the safety of material handling, making it particularly suitable for scenarios with high material stability requirements. The top plate 1 also features a control board 5 connected to the power unit 2.

[0023] like Figure 1-3As shown: The power unit 2 includes a motor 21 fixed to the top surface of the top plate 1. Second bearing seats 36 are fixed to both sides of the motor 21 on the top surface of the top plate 1. The motor 21 is connected to the control board 5. A transmission mechanism 22 is connected to the output end of the motor 21, and a coupling 211 is connected to the output end of the motor 21. The output end of the transmission mechanism 22 is connected to the lower movable end of the scissor lift rod 31; the upper movable end of the scissor lift rod 31 is connected to the upper sliding assembly 321. The transmission mechanism 22 includes a lead screw 23 connected to the output end of the motor 21. First bearing seats 24 are fixed to both ends of the lead screw 23 on the top plate 1. A lead screw slider 25 is fitted inside the first bearing seats 24 on the lead screw 23. The lower movable end of the scissor lift rod 31 is mounted on the lead screw slider 25. A connecting layer 26 is fitted over the lead screw slider 25. Connecting rods 27 are fixed to both sides of the connecting layer 26, and a first movable slider 28 is fixed to the end of each connecting rod 27. The bottom end of the first inclined rod 34 is hinged to the connecting rod 27; the bottom end of the second inclined rod 35 is hinged to the second bearing seat 36, and the bottom end of the first inclined rod 34 serves as the lower movable end of the scissor lift rod 31; a third bearing seat 37 is fixed on the bottom surface of the lifting plate 32 and above the second bearing seat 36, and the third bearing seat 37 is hinged to the top end of the first inclined rod 34, and the top end of the first inclined rod 34 serves as the upper fixed end of the scissor lift rod 31; the bottom end of the second inclined rod 35 is hinged to the second bearing seat 36, and the bottom end of the second inclined rod 35 serves as the lower fixed end of the scissor lift rod 31; the top end of the second inclined rod 35 is connected to the upper sliding assembly 321, and the top end of the second inclined rod 35 serves as the upper movable end of the scissor lift rod 31. A first slide rail 29 is provided on the top surface of the top plate 1 and below the first movable slider 28, the first slide rail 29 is engaged with the first movable slider 28 and the first movable slider 28 slides within the first slide rail 29. The first slide rail 29 on the top plate 1 engages with the first movable slider 28, providing a fixed movement path for the first movable slider 28 and restricting it to slide only along the slide rail direction, effectively preventing slider deviation. This design ensures that the trajectory of the lead screw slider 25 driving the first movable slider 28 through the connecting rod 27 is regular, thereby ensuring synchronous and stable movement of the scissor lift arm 31. The upper sliding assembly 321 includes a second slide rail 38 located on the bottom surface of the lifting plate 32 and correspondingly above the first slide rail 29. A second movable slider 39 engages within the second slide rail 38 and slides within the second slide rail 38. The second movable slider 39 is hinged to the top end of the second inclined rod 35. The inner hole of the lead screw slider 25 is machined with an internal thread that is completely matched with the external thread of the lead screw 23. The two are connected by a thread pair to form a transmission structure that can convert the rotational motion of the motor 21 into the linear motion of the lead screw slider 25, and then transmit it to the lifting part 3 through the connecting rod 27. This ensures that the height adjustment of the scissor arm lifting rod 31 and the lifting plate 32 strictly follows the preset trajectory and speed, effectively avoiding lifting deviation or swaying, and accurately adapting to the precision requirements of high-level docking such as printing machines and coating machines, reducing material loss and equipment downtime caused by docking deviation.Meanwhile, the first bearing seat 24 is fixed to the top surface of the top plate 1, providing stable axial and radial support for the lead screw 23, preventing it from bending and deforming during high-speed rotation or when carrying materials. This also reduces frictional loss and extends service life. Furthermore, the rigid connection between the lead screw slider 25 and the connecting rod 27 evenly distributes the weight of the material, preventing localized stress concentration that could damage components. This ensures stable operation of the device even when carrying heavy printing materials, improving the overall structural load-bearing capacity and durability. In addition, this transmission structure forms a continuous power transmission path, enabling efficient collaboration with the scissor lift rod 31, which is cross-hinged with the lifting unit 3. The linear movement of the lead screw slider 25 precisely drives the scissor lift rod 31 to extend or retract. Moreover, the adjustability of the lead screw 23 transmission (controlled by the speed of the motor 21) is compatible with the lifting speed control function of the control board 5, flexibly meeting the needs of slow and stable docking at low workstations and efficient adjustment at high workstations, thus optimizing the automated collaborative effect. In addition, couplings 211 and lead screws 23 are all industrial standard components, which are convenient to purchase and have simple connection methods. Damaged parts can be quickly disassembled and replaced during later maintenance without the need to modify the entire transmission mechanism. At the same time, the lead screw 23 transmission is less prone to jamming, dust accumulation and wear problems compared to gear and chain transmission. Only simple lubrication is required in daily use, which greatly reduces the workload and cost of maintenance and improves the cost-effectiveness of equipment use.

[0024] Workflow: When needed, the AGV moves from its designated location to the material to be transported. Control board 5 controls the output of motor 21 to rotate. The output of motor 21, via coupling 211, drives lead screw 23 to rotate, causing lead screw slider 25 on lead screw 23 to slide. This, in turn, causes the first movable slider 28, fixed to the ends of connecting rods 27 on both sides of the outer connecting layer 26 of lead screw slider 25, to slide within the first slide rail 29. The bottom end of the first inclined rod 34 serves as the lower movable end of the scissor arm lifting rod 31, hinged to the connecting rod 27. The bottom end of the second inclined rod 35 serves as the lower fixed end of the scissor arm lifting rod 31, hinged to the second bearing seats 36 fixed to the top surface of the top plate 1 and on both sides of motor 21. The top end of the first inclined rod 34 serves as the scissor arm... The upper fixed end of the lifting rod 31 is hinged to a third bearing seat 37 fixed to the bottom surface of the lifting plate 32 and above the second bearing seat 36. The top end of the second inclined rod 35 serves as the upper movable end of the scissor lift 31 and is hinged to the second movable slider 39 that slides in the second slide rail 38. Since the first inclined rod 34 and the second inclined rod 35 are centrally intersecting and hinged at the intersection, the second inclined rod 35 moves synchronously when the first inclined rod 34 moves, thereby driving the lifting plate 32 and the V-shaped limit block 33 fixed on the lifting plate 32 to move vertically. When the V-shaped limit block 33 moves to the required position, the motor 21 stops rotating. After the material is picked up, the AGV trolley moves to the material receiving position. After adjusting the position of the device, the material is picked up by the machine, and the AGV trolley returns to the standby position.

Claims

1. A scissor lift handling and docking device for AGV trolleys, characterized in that: The AGV includes a top plate (1) installed above the AGV trolley. The top plate (1) has a power unit (2) on both sides. The output end of the power unit (2) has a lifting unit (3). The lifting unit (3) includes a scissor arm lifting rod (31) installed at the output end of the power unit (2). The top of the scissor arm lifting rod (31) has a lifting plate (32). The top surface of the lifting plate (32) has a V-shaped limiting block (33) for supporting materials. The top plate (1) also has a control plate (5) connected to the power unit (2).

2. The scissor lift handling and docking device for AGV trolleys according to claim 1, characterized in that: The power unit (2) includes a motor (21) fixed on the top surface of the top plate (1). The output end of the motor (21) is connected to a transmission mechanism (22). The output end of the transmission mechanism (22) is connected to the lower movable end of the scissor lift rod (31). The lifting plate (32) is provided with an upper sliding assembly (321). The upper movable end of the scissor lift rod (31) is connected to the upper sliding assembly (321).

3. The scissor lift handling and docking device for AGV trolleys according to claim 2, characterized in that: The transmission mechanism (22) includes a lead screw (23) connected to the output end of the motor (21). The two ends of the lead screw (23) are provided with first bearing seats (24) fixed on the top plate (1). A lead screw slider (25) is sleeved on the lead screw (23) and inside the first bearing seat (24). The lower movable end of the scissor arm lifting rod (31) is set on the lead screw slider (25).

4. The scissor lift handling and docking device for AGV trolleys according to claim 3, characterized in that: The lead screw slider (25) is covered with a connecting layer (26), and connecting rods (27) are fixed on both sides of the connecting layer (26). A first movable slider (28) is fixed at the end of the connecting rods (27).

5. The scissor lift handling and docking device for AGV trolleys according to claim 4, characterized in that: The top surface of the top plate (1) and below the first movable slider (28) are provided with a first slide rail (29), the first slide rail (29) is engaged with the first movable slider (28) and the first movable slider (28) slides within the first slide rail (29).

6. The scissor lift handling and docking device for AGV trolleys according to claim 5, characterized in that: The top surface of the top plate (1) and both sides of the motor (21) are fixed with second bearing seats (36).

7. The scissor lift handling and docking device for AGV trolleys according to claim 6, characterized in that: The scissor lift rod (31) includes a first inclined rod (34) and a second inclined rod (35), which are centrally intersecting and hinged at the intersection; the bottom end of the first inclined rod (34) is hinged to the connecting rod (27), and the bottom end of the first inclined rod (34) serves as the lower movable end of the scissor lift rod (31); a third bearing seat (37) is fixed on the bottom surface of the lifting plate (32) and above the second bearing seat (36), and the third bearing... The seat (37) is hinged to the top of the first inclined rod (34), and the top of the first inclined rod (34) serves as the upper fixed end of the scissor arm lifting rod (31); the bottom end of the second inclined rod (35) is hinged to the second bearing seat (36), and the bottom end of the second inclined rod (35) serves as the lower fixed end of the scissor arm lifting rod (31); the top of the second inclined rod (35) is hinged to the upper sliding assembly (321), and the top of the second inclined rod (35) serves as the upper movable end of the scissor arm lifting rod (31).

8. The scissor lift handling and docking device for AGV trolleys according to claim 7, characterized in that: The upper sliding assembly (321) includes a second slide rail (38) disposed on the bottom surface of the lifting plate (32) and at a corresponding position above the first slide rail (29). A second movable slider (39) is fitted inside the second slide rail (38). The second movable slider (39) slides inside the second slide rail (38). The second movable slider (39) is hinged to the top end of the second inclined rod (35).

9. The scissor lift handling and docking device for AGV trolleys according to claim 2, characterized in that: The output end of the motor (21) is connected to a coupling (211), and the output end of the motor (21) is connected to the transmission mechanism (22) through the coupling (211).

10. The scissor lift handling and docking device for AGV trolleys according to claim 1, characterized in that: The V-shaped limiting block (33) includes two symmetrical blocks (331) that are inclined towards the middle, and a limiting groove (332) is formed between the symmetrical blocks (331). The symmetrical blocks (331) are fixed to the lifting plate (32).

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