Mobile electrical test operating platform

Abstract

The invention discloses a mobile electrical test operation table, and aims to solve the problems that an existing test operation table is poor in portability, insufficient in stability and inconvenient in cable management. The operating table comprises a bottom plate and an operating table structure, universal wheels are arranged at the bottom of the bottom plate, and the operating table structure is connected with the bottom plate through a supporting structure. The operation table structure comprises a first table board and a second table board which are connected in a foldable mode through a hinge piece, and a table board is fixed in cooperation with an insertion groove and an insertion plate. A power connection box is arranged at the bottom of the second platen. The supporting structure adopts a telescopic supporting pipe and a supporting rod, and a sliding block and a sliding groove are combined to achieve folding and unfolding of the table top. Threaded rods and non-slip mats are arranged at two ends of the bottom plate to adapt to uneven ground. Through the design of the universal wheels, the hand-push frame, the foldable table top and the power supply connecting box, the portability, the stability and the cable management efficiency are improved, and the device is suitable for the field test of the transformer substation.

Description

Technical Field

[0001] The present invention belongs to the technical field of auxiliary equipment for on-site tests in power engineering, and particularly relates to a mobile electrical test operation platform, which is applicable to on-site test environments in power engineering such as substations and provides a stable operation platform for test instruments. Background Art

[0002] With the rapid development of the power industry, substations, as important nodes in the power system, have increasingly frequent construction and maintenance work. In recent years, substation projects have entered a peak construction period, and the number of projects involving infrastructure handover tests, equipment maintenance tests, and daily maintenance tests has increased significantly every year. These tests usually require the use of various instruments and meters, such as voltmeters, ammeters, insulation resistance testers, etc. The test process has high requirements for instrument accuracy, wiring specifications, and the on-site environment. However, there are many problems in the prior art in substation on-site tests, seriously affecting test efficiency and data accuracy.

[0003] Firstly, the traditional test method usually directly places the instruments and meters on the ground or a simple platform temporarily built. This method easily causes the instruments to be contaminated by dust, moisture, or other sundries, thus shortening the service life of the instruments or reducing the measurement accuracy. For example, there may be sand or water accumulation on the ground at the substation site. When the instruments are directly in contact with the ground, they are prone to getting dirty or being affected by moisture, thereby affecting the reliability of the test results. In addition, the instruments placed on the ground lack stable support and are easily displaced due to vibration or collision, resulting in loose wiring or interrupted measurement.

[0004] Secondly, the management problem of test cables is also a major defect in the prior art. Substation on-site tests involve multiple instruments, with complex and numerous wiring. The cables are usually scattered randomly on the ground and are prone to being intertwined. This disorderly cable arrangement not only increases the risk of wiring errors but also may cause electromagnetic interference, resulting in deviations in test data. For example, if the signal cables of different instruments are close to high-voltage cables, noise may be generated due to electromagnetic coupling, affecting the measurement accuracy. In addition, the scattered cables also pose a risk of being stepped on or pulled, increasing the safety risk at the test site.

[0005] Thirdly, the portability and adaptability of existing test operation platforms are insufficient and difficult to meet the diverse needs of substation on-site tests. Substation test sites are usually distributed in different areas with different terrains and ground conditions. For example, some sites may be uneven soil ground or temporarily built platforms. Traditional fixed operation platforms are large in volume and heavy in weight, making it difficult to carry and install them and unable to quickly adapt to the requirements of different test sites. Some portable operation platforms, although light in weight, have a simple structure and poor stability, and are difficult to bear the weight of multiple instruments or frequent operations. In addition, most existing operation platforms do not have a folding function, occupying a large amount of space during transportation and storage, increasing the complexity of logistics management.

[0006] Fourth, the existing operating console lacks an effective power management design. In substation on-site tests, instruments usually require external power support, but the existing operating consoles often do not have integrated power connection devices, and testers need to arrange power cords additionally. This method not only increases the wiring workload but also raises the probability of wiring errors due to the mixing of power cords and signal lines, affecting the test efficiency. At the same time, the random placement of power cords may also cause safety hazards such as tripping or short circuits, especially in crowded or narrow test sites.

[0007] Finally, the existing operating console has insufficient adaptability to complex test environments. There may be problems such as uneven ground, limited space, or variable environments at substation sites. Traditional operating consoles lack flexible adjustment mechanisms, such as height adjustment or ground stabilizing devices, and it is difficult to maintain stability under different conditions. Although some operating consoles are equipped with simple support structures, their adjustment ranges are limited and the fixing methods are complex, making it difficult to quickly complete installation and disassembly, resulting in too long test preparation time.

[0008] In summary, the existing technologies face problems such as easy dirt and damage of instruments, chaotic cable management, insufficient portability and stability of operating consoles, inconvenient power management, and poor environmental adaptability in substation on-site tests. There is an urgent need for a test auxiliary device that can effectively solve the above problems to improve test efficiency, data accuracy, and on-site safety. Summary of the Invention

[0009] In view of this, the purpose of the present invention is to provide a mobile electrical test operating console to solve the problems of poor portability, insufficient stability, and inconvenient cable management of the test operating console in the existing technology. Through designs such as a foldable operation tabletop, a universal wheel moving structure, a telescopic support structure, and a power connection box, the present invention improves the portability, stability, and practicality of the operating console.

[0010] To achieve the above purpose, the present invention provides the following technical solutions:

[0011] A mobile electrical test operating console includes a bottom plate and an operating console structure provided on the bottom plate. Universal wheels are provided at the bottom of the bottom plate, and a support structure is provided at the bottom end of the operating console structure. The operating console structure is connected to the bottom plate through the support structure; the operating console structure includes a table board one and a table board two that are foldably connected, and the table board one and the table board two are connected through a hinge member to realize the folding and flattening of the operation tabletop; a hand push frame is also provided on the bottom plate on one side of the operating console structure for pushing the bottom plate to move.

[0012] Preferably, the operating table structure includes two first table boards, one ends of the two first table boards are placed opposite to each other, and a second table board is placed between the two first table boards. Two opposite ends of the two first table boards are respectively hinged and fixed to two ends of the second table board through hinge members.

[0013] Preferably, slots are provided at the bottoms of two opposite ends of the two first table boards, and inserting plates are movably inserted into the slots. A slot is also provided at the bottom of the second table board; when the operating table surface is flattened, the inserting plates extend from the slots at the bottoms of the first table boards into the slots at the bottom of the second table board to fix the first table boards and the second table board.

[0014] Preferably, a power connection box is fixedly provided at the bottom of the second table board.

[0015] Preferably, a plurality of the support structures are vertically arranged between the bottom plate and the operating table structure. The support structure includes a support tube and a support rod. One end of the support tube is connected to the first table board through a hinge member, and the other end inserts the support rod. The support rod and the support tube are slidably matched to realize the telescoping of the support structure; a hand-tightening bolt is provided on one side of the support tube. By screwing the hand-tightening bolt, one end of it abuts against the support rod to lock the support rod.

[0016] Preferably, a chute is provided on the bottom plate, and a slider is connected to the bottom of the support structure. The slider is slidably arranged in the chute. By pushing the slider to move, the folding and flattening of the operating table surface are realized; a hand-tightening bolt is also provided on the slider for locking the slider.

[0017] Preferably, threaded tubes are provided at both ends of the bottom plate, threaded rods are threadedly connected in the threaded tubes, and anti-slip pads are provided at the bottom ends of the threaded rods. By rotating the threaded rods, the height adjustment of the anti-slip pads can be realized.

[0018] Preferably, the universal wheels are respectively arranged at four corner positions close to the bottom of the bottom plate.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. Significantly improve portability and meet the test requirements of multiple scenarios: By arranging universal wheels at the bottom of the bottom plate and equipping with a hand push frame in the present invention, the convenient movement of the operating table is realized. The universal wheels are installed at four corner positions of the bottom plate to ensure the stability and flexibility during the movement, so that the operating table can easily meet the switching requirements of different test sites in the substation. Compared with the traditional fixed operating table or heavy mobile equipment, the design of the present invention greatly reduces the handling difficulty, reduces the test preparation time, and improves the flexibility and efficiency of on-site tests.

[0021] 2. Foldable design to optimize storage and transportation efficiency: The operating table adopts table board one and table board two which are foldably connected, and the folding and flattening of the operating table surface are realized through hinge parts. In the flattened state, the slot and plug mechanism further fixes table board one and table board two to form a stable operating platform; in the folded state, the volume of the operating table is significantly reduced, occupying less space and being convenient for storage and transportation. This design solves the defect of the existing operating table with a large volume and being difficult to store, and is especially suitable for the scenarios of frequent handling and limited space at the substation site.

[0022] 3. Enhance structural stability to ensure test accuracy: The support structure of the present invention adopts the telescopic design of support pipes and support rods, combined with the hand-tightening bolt locking mechanism, which can flexibly adjust the height of the operating table and ensure the structural stability. The slider and chute mechanism further optimizes the folding and flattening process of the table surface, and at the same time locks the slider with a hand-tightening bolt to prevent the table surface from shaking during the operation. These designs effectively improve the overall stability of the operating table, enabling it to bear the weight of various test instruments and the impact of frequent operations, reducing the risk of instrument displacement or wiring loosening, and thus ensuring the accuracy of test data.

[0023] 4. Standardize cable management to improve safety and efficiency: By setting a power connection box at the bottom of table board two, the present invention realizes the centralized management and standardized connection of test cables. The power connection box can integrate power lines and signal lines, avoiding the scattered arrangement of cables, and significantly reducing the probability of wiring errors and electromagnetic interference. Compared with the existing technology that requires additional power line layout, this design simplifies the wiring process, reduces the test preparation time, and at the same time reduces the safety hazards of cables being trampled or short-circuited, providing higher safety for the test site.

[0024] 5. Adapt to complex environments to improve on-site applicability: The present invention sets threaded pipes and threaded rods at both ends of the bottom plate, and the bottom end of the threaded rod is equipped with an anti-slip pad. By rotating the threaded rod, the height of the anti-slip pad can be adjusted to keep the operating table stable on uneven ground. This design solves the problem of insufficient stability of the existing operating table on complex terrains (such as soil ground or temporary platforms). In addition, the combination of universal wheels and telescopic support structures enables the operating table to quickly adapt to different height and space requirements, further enhancing its applicability in the changing environment of the substation site.

[0025] 6. Simple operation to improve user experience: All functional components of the present invention adopt manual adjustment designs, such as hand-tightening bolts, plug boards and threaded rods. The operation is simple and the flattening, fixing, height adjustment and folding of the table surface can be completed without additional tools. This user-friendly design reduces the operation difficulty of test personnel, especially in the time-consuming on-site environment, which can significantly improve work efficiency and improve user experience.

[0026] Other advantages, objectives, and features of the present invention will, to some extent, be elaborated in the subsequent description, and to some extent, will be obvious to those skilled in the art based on the examination and research of the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following description. Description of the Drawings

[0027] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0028] Figure 1 It is a schematic structural diagram of the mobile electrical test operation console in the present invention.

[0029] Figure 2 is Figure 1 the enlarged view at A in

[0030] Reference numerals: 1 - bottom plate; 2 - sliding groove; 3 - universal wheel; 4 - threaded pipe; 5 - threaded rod; 6 - anti-slip pad; 7 - hand push frame; 8 - support rod; 9 - support pipe; 10 - hand-tightening bolt; 11 - hinge piece; 12 - table plate one; 13 - table plate two; 14 - hinge member; 15 - slot; 16 - plug board; 17 - slider; 18 - power connection box. Detailed Embodiment

[0031] The following uses specific specific examples to illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0032] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and cannot be understood as a limitation to the present invention; for better illustrating the embodiments of the present invention, some components in the drawings will be omitted, enlarged, or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0033] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the accompanying drawings are only for illustrative purposes and should not be construed as a limitation of the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0034] Embodiment 1: Standard Mobile Electrical Test Console

[0035] As Figure 1 and Figure 2 shown, this embodiment provides a standard mobile electrical test console applicable to the conventional test scenarios of substations. The console includes a bottom plate 1, and universal wheels 3 are provided at positions close to the four corners at the bottom of the bottom plate 1. An operating console structure is provided on the bottom plate 1, a support structure is provided at the bottom end of the operating console structure, and the operating console structure is connected to the bottom plate 1 through the support structure. A hand push frame 7 is also provided on the bottom plate 1.

[0036] Operating console structure: The operating console structure includes two first platform plates 12 and a second platform plate 13. One end of the two first platform plates 12 is placed opposite to each other, and the second platform plate 13 is placed between the two first platform plates 12. The opposite ends of the two first platform plates 12 are hinged and fixed to both ends of the second platform plate 13 through hinge members 14. The hinge members 14 are made of stainless steel to ensure durability for long-term use. Slots 15 are provided at the bottom of the opposite ends of the two first platform plates 12, and insertion plates 16 are movably inserted into the slots 15. Slots 15 are also provided at the bottom of the second platform plate 13. When flattening the operating tabletop, the insertion plate 16 extends from the slot 15 of the first platform plate 12 into the slot 15 of the second platform plate 13 to fix the first platform plate 12 and the second platform plate 13 to form a flat operating platform. A power connection box 18 is fixedly provided at the bottom of the second platform plate 13. The power connection box 18 includes multiple standard sockets and grounding ports for connecting the power cords and signal lines of test instruments.

[0037] Support structure: Four support structures are vertically arranged between the bottom plate 1 and the operating table structure. Each support structure includes a support tube 9 and a support rod 8. One end of the support tube 9 is connected to the first table board 12 through a hinge 11, and the other end is inserted with the support rod 8. The support rod 8 is in sliding fit with the support tube 9, and the height of the operating table can be adjusted to 800 - 1200 mm. A hand-tightening bolt 10 is provided on one side of the support tube 9. By turning the hand-tightening bolt 10, it abuts against the support rod 8 to lock the support rod 8. Two chutes 2 are provided on the bottom plate 1. The bottoms of the two support rods 8 are connected with sliders 17. The sliders 17 are slidably arranged in the chutes 2. By pushing the sliders 17 to move, the folding and flattening of the operating tabletop are realized. A hand-tightening bolt 10 is provided on the slider 17 for locking the slider 17 to ensure the stability after the tabletop is flattened.

[0038] Bottom plate and fixing structure: Threaded tubes 4 are provided at both ends of the bottom plate 1. A threaded rod 5 is threadedly connected in the threaded tube 4. An anti-slip pad 6 made of rubber is provided at the bottom end of the threaded rod 5. By rotating the threaded rod 5, the height of the anti-slip pad 6 can be adjusted, and the adjustment range is 0 - 50 mm to adapt to uneven ground. The universal wheels 3 are made of high-strength polyurethane material, with a diameter of 100 mm and a braking function to ensure flexibility during movement and fixation.

[0039] Working principle and usage process:

[0040] Moving and fixing: Push the operating table through the hand push frame 7, and use the universal wheels 3 to move it to the test position. After arriving, rotate the threaded rod 5 to make the anti-slip pad 6 abut against the ground, fix the bottom plate 1, and step on the brake of the universal wheels 3 to lock the wheels.

[0041] Flatten the tabletop: Push the slider 17 to move along the chute 2, so that the first table board 12 and the second table board 13 are unfolded to the horizontal state through the hinge parts 14. Insert the insertion plate 16 from the slot 15 of the first table board 12 into the slot 15 of the second table board 13 to fix the operating tabletop. Tighten the hand-tightening bolt 10 on the slider 17 to lock the slider 17.

[0042] Height adjustment: Adjust the position of the support rod 8 in the support tube 9 to a suitable height (such as 1000 mm), and tighten the hand-tightening bolt 10 to lock the support rod 8 to complete the fixation of the tabletop.

[0043] Cable connection: Connect the power cord and signal line of the test instrument to the power connection box 18 to ensure standard wiring.

[0044] Folding and storage: After the test is completed, loosen the hand-tightening bolt 10 and the insertion plate 16, push the slider 17 to fold the first table board 12 and the second table board 13 through the hinge parts 14 to reduce the volume. Loosen the threaded rod 5, release the brake of the universal wheels 3, and move the operating table to the storage position.

[0045] This embodiment is suitable for conventional substation tests. The tabletop area is moderate (about 1.2m×0.8m), capable of carrying 50kg of instruments, taking into account both portability and stability.

[0046] Embodiment 2: Enhanced Mobile Electrical Test Operating Table

[0047] As Figure 1 and Figure 2 shown, this embodiment provides an enhanced mobile electrical test operating table, which is applicable to substation tests in complex environments, such as outdoor uneven ground or high-load test scenarios. This embodiment optimizes the structural dimensions and materials on the basis of Embodiment 1, enhancing stability and adaptability.

[0048] Operating Table Structure: The operating table structure includes two first table plates 12 and one second table plate 13. The first table plates 12 and the second table plate 13 are made of aluminum alloy material, with an anti-slip coating on the surface to enhance durability and the stability of instrument placement. One end of the two first table plates 12 is placed opposite to each other, and the second table plate 13 is placed between them, and is hinged and fixed to both ends of the second table plate 13 through high-strength stainless steel hinge parts 14. The bottoms of the two first table plates 12 are provided with deepened slots 15 (depth 150mm), and thickened insertion plates 16 (thickness 10mm) are inserted into the slots 15. The bottom of the second table plate 13 is provided with slots 15 that match the slots 15. When the tabletop is unfolded, the insertion plate 16 is inserted into the slot 15 of the second table plate 13 to fix the first table plate 12 and the second table plate 13, forming a large operating platform of 1.5m×1.0m. The bottom of the second table plate 13 is fixedly provided with an enhanced power connection box 18, which includes 6 sockets, 2 USB interfaces and an overload protection device, supporting the simultaneous connection of multiple instruments.

[0049] Support Structure: Six support structures are vertically arranged between the bottom plate 1 and the operating table structure to increase the support points to improve stability. Each support structure includes a thickened support tube 9 (diameter 50mm) and a support rod 8. The support tube 9 is connected to the first table plate 12 through a high-strength hinge part 11. The support rod 8 is slidably matched with the support tube 9, and the height adjustment range is 900 - 1400mm to adapt to different operation requirements. Two hand-tightening bolts 10 are provided on one side of the support tube 9 to enhance the locking force. Three widened sliding grooves 2 (width 40mm) are provided on the bottom plate 1. The bottoms of the three support rods 8 are connected with sliders 17, and the sliders 17 are slidably arranged in the sliding grooves 2. The tabletop is folded and unfolded by pushing the sliders 17. Two hand-tightening bolts 10 are provided on the sliders 17 to ensure firm locking.

[0050] Bottom Plate and Fixing Structure: The bottom plate 1 is made of steel plate material, with a size of 1.6m×1.2m to enhance the bearing capacity. Four threaded tubes 4 are provided at both ends of the bottom plate 1. A threaded rod 5 is connected inside the threaded tube 4, and a high-friction silicone anti-slip pad 6 is provided at the bottom end of the threaded rod 5. The adjustment range is 0 - 80mm to adapt to complex terrains. The universal wheels 3 are made of heavy-duty polyurethane wheels, with a diameter of 150mm and a double-brake mechanism, and the bearing capacity reaches 200kg.

[0051] Working principle and usage process:

[0052] Moving and fixing: Push the operating table through the hand push frame 7, and use the universal wheels 3 to move it to the outdoor test position. Rotate the four threaded rods 5 to make the anti-slip pads 6 fit against the uneven ground, adjust it to a horizontal state, and step on the double brakes of the universal wheels 3 to fix the bottom plate 1.

[0053] Expanding the platform surface: Push the slider 17 along the widened chute 2 to expand the table board one 12 and the table board two 13 through the hinge parts 14. Insert the thickened plug board 16 into the slot 15 of the table board two 13 to fix the table surface. Tighten the two hand-tightening bolts 10 on the slider 17 to lock the slider 17.

[0054] Height adjustment: Adjust the support rod 8 to the required height (for example, 1200 mm), tighten the two hand-tightening bolts 10 on the support tube 9 to lock the support rod 8, and ensure the stability of the table surface.

[0055] Cable connection: Connect the power cords, signal lines, and data lines of multiple test instruments to the power connection box 18, and the overload protection device ensures the safety of the wiring.

[0056] Folding and storing: After the test is completed, loosen the hand-tightening bolts 10 and the plug board 16, and push the slider 17 to fold the table surface. Loosen the threaded rod 5, release the brake of the universal wheels 3, and move the operating table to the storage area.

[0057] This embodiment is suitable for high-load and complex environment tests. The bearing capacity of the table surface reaches 100 kg, and it can adapt to the changing terrain outdoors and the test requirements of multiple instruments.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A mobile electrical test operation console, characterized in that: It includes a bottom plate and an operating table structure provided on the bottom plate. Universal wheels are provided at the bottom of the bottom plate, and a support structure is provided at the bottom end of the operating table structure. The operating table structure is connected to the bottom plate through the support structure. The operating table structure includes a first table board and a second table board that are foldably connected. The first table board and the second table board are connected by a hinge member to realize the folding and flattening of the operating table surface. A hand push frame is also provided on the bottom plate on one side of the operating table structure for pushing the bottom plate to move.

2. The mobile electrical test console according to claim 1, characterized in that: The operating table structure includes two first table boards. One ends of the two first table boards are placed opposite to each other, and the second table board is placed between the two first table boards. The opposite ends of the two first table boards are respectively hinged and fixed to both ends of the second table board through hinge members.

3. The mobile electrical test operation console according to claim 2, wherein: Slots are provided at the bottoms of the opposite ends of the two first table boards. Insert plates are movably inserted into the slots. A slot is also provided at the bottom of the second table board. When the operating table surface is flattened, the insert plates extend from the slots at the bottom of the first table board into the slots at the bottom of the second table board to fix the first table board and the second table board.

4. A mobile electrical test operation console according to claim 3, characterized in that: A power connection box is also fixedly provided at the bottom of the second table board.

5. A mobile electrical test console according to claim 3, characterized in that: Multiple support structures are vertically arranged between the bottom plate and the operating table structure. The support structure includes a support tube and a support rod. One end of the support tube is connected to the first table board through a hinge member, and the other end inserts the support rod. The support rod and the support tube are slidably matched to realize the telescoping of the support structure. A hand-tightening bolt is provided on one side of the support tube. By turning the hand-tightening bolt, one end of it abuts against the support rod to lock the support rod.

6. The mobile electrical test console according to claim 5, characterized in that: A chute is provided on the bottom plate. The bottom of the support structure is connected with a slider. The slider is slidably arranged in the chute. By pushing the slider to move, the folding and flattening of the operating table surface are realized. A hand-tightening bolt is also provided on the slider for locking the slider.

7. A mobile electrical test operation console according to claim 1, characterized in that: Threaded tubes are provided at both ends of the bottom plate. Threaded rods are threadedly connected in the threaded tubes. An anti-slip pad is provided at the bottom end of the threaded rod. The height of the anti-slip pad can be adjusted by rotating the threaded rod.

8. A mobile electrical test operation console according to claim 1, characterized in that: The universal wheels are respectively provided at four corner positions close to the bottom of the bottom plate.

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