Adjustable height saw
By using a plug-in push-press structure and a V-shaped guide, the design solves the problems of poor adaptability and inconvenient operation caused by the fixed height of traditional saws, and achieves flexible height adjustment and stable locking, thus improving the user's ease of operation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- JINHUA YAHU TOOLS
- Filing Date
- 2025-08-13
- Publication Date
- 2026-07-31
AI Technical Summary
Traditional saws have a fixed height design, which makes them unsuitable for users of different heights and for diverse processing needs, and they are also inconvenient to operate.
The synchronous movement of the locking pins on both sides is controlled by a plug-in push-press structure. The locking pins are easily operated by a V-shaped guide and a return spring. The lifting switch is exposed to the external space, increasing the operating space.
It achieves flexible adjustment and stable locking of the saw height, improving ease of operation and applicability, and adapting to users of different heights and processing needs.
Smart Images
Figure CN224575838U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of woodworking auxiliary tools, specifically to a saw that is easy to adjust in height. Background Technology
[0002] Wood saws, used as temporary platforms to support long, large-sized planks in wood processing, are widely used in construction, furniture making, and outdoor wood cutting. Traditional wood saws are mostly designed with a fixed height, resulting in poor adaptability and difficulty in meeting diverse needs, such as users with varying heights or different wood processing scenarios.
[0003] Existing patent CN218613915U discloses a height-adjustable saw, which allows manual adjustment of the position of the limiting pin via a handle, facilitating the adjustment of the telescopic outriggers to the appropriate position and improving adjustment efficiency and convenience. However, the handle in this design is installed inside a handle window, which is only located on the crossbeam body. As can be seen from the attached drawings, the operating space of the handle is limited, making it inconvenient to operate. Furthermore, when adjusting the two telescopic outriggers on the same side, the handle must be moved twice, or both handles must be moved simultaneously with one hand, a cumbersome and inconvenient process. Summary of the Invention
[0004] The purpose of this utility model is to overcome the shortcomings of the existing technology and provide a saw that is easy to adjust in height. By setting up a plug-in push-press structure to control the movement of the locking pins on both sides, the ease of operation is improved. Furthermore, most of the lifting switch that controls the start of the plug-in push-press structure is exposed in the external space, making the operating space of the lifting switch more free and further improving the ease of operation.
[0005] To solve the above problems, the present invention adopts the following solution: A height-adjustable saw includes a support beam and paired support legs located at the lower end of the support beam. At least one set of support legs is rotatably hinged to the support beam. Each set of support legs includes two support rods, each support rod including a lifting rod that can extend its length by sliding up and down. A crossbar is provided between the two support rods in each set, and a locking assembly is fitted between the crossbar on each side and the support legs. The locking assembly is symmetrically arranged and used to control the stable connection or disengagement of the crossbar and the lifting rod, and includes: Multiple locking pin holes are distributed along the length of the lifting rod; Two sets of locking pins, as the direct actuators for locking the components, can be detachably inserted into the locking pin holes of the lifting legs on both sides. The plug-in push-press structure is movably connected to the cross frame plate and is used to drive the two locking pins to disengage from the locking pin holes at the same time, or to push the two locking pins into the corresponding locking pin holes at the same time to achieve locking.
[0006] Preferably, the insertion and pushing structure includes: Two push-fit components are connected to two sets of locking pins respectively, serving as push components to drive the locking pins into or out of the locking pin holes; The V-shaped guide is symmetrically arranged and has two first guide ramps. The longitudinal movement of the V-shaped guide is converted into a lateral push on the two plug-in pushers through the two first guide ramps. The lifting switch, as a driving component that controls the disengagement of the locking pin from the locking pin hole, abuts against the lower end of the V-shaped guide, is movably connected to the crossbeam plate, and is exposed below the crossbeam plate. The restoring spring is located between the two plug-in push parts, and its elastic force is set in the horizontal direction. When the lifting switch is released, the spring force can be used to push the locking pin into the locking pin hole to relock.
[0007] In the above scheme, the locking component is in a locked state by default. Pressing the lifting switch pushes the V-shaped guide upwards, which then disengages the locking pin from the locking pin hole via two plug-in pushers. The lifting rod is then moved to adjust the height of the support frame. Once adjusted, the lifting switch is released, and the restoring spring's elasticity pushes the locking pin back into the locking pin hole, locking it in place. Simultaneously, the plug-in pushers, via the V-shaped guide, push the lifting switch back to its initial state. Furthermore, the lifting switch in this scheme is plate-shaped and exposed below the crossbeam, allowing for flexible operation and easy adjustment.
[0008] Preferably, the support leg also includes a fixed foot sleeve and a stabilizing connecting sleeve fixedly fitted to the lower end of the fixed foot sleeve. The lifting leg passes through the stabilizing connecting sleeve and slides within the slide rail of the fixed foot sleeve, wherein the crossbar is connected between the two stabilizing connecting sleeves.
[0009] The above configuration enables the support legs to slide and extend while also achieving triple coupling, ensuring the sliding stability of the lifting rod and the support stability of the support legs.
[0010] Preferably, the plug-in pusher has a sloping guide hole with a second guide slope. During the up-and-down movement of the V-shaped guide, the first guide slope and the second guide slope abut against each other and the abutment area changes accordingly.
[0011] Therefore, the mutual conversion between the vertical movement of the V-shaped guide and the lateral movement of the insertion and pressing component is realized.
[0012] Preferably, the V-shaped guide member also includes a guide limiting structure, comprising a directional slide rod located in the middle of the V-shaped guide member and limiting protrusions on both sides. The directional slide rod is slidably inserted into the longitudinal guide groove of the crossbeam plate, and the bends of the two limiting protrusions can be separated and engaged with the end corners of the two limiting bosses on the crossbeam plate. When the lifting switch is in the default position, the bends of the limiting protrusions are engaged with the end corners of the limiting bosses.
[0013] In the above scheme, the directional sliding rod and longitudinal guide groove ensure stable longitudinal movement of the V-shaped guide, thereby ensuring that the locking pins on both sides can be accurately and synchronously inserted into the locking pin holes. The limiting protrusion hook and limiting boss provide a limiting and stabilizing effect on the V-shaped guide, making it less prone to deviation during the up and down movement of the V-shaped guide. Therefore, the first guide slope on it can stably abut against the second guide slope, which can further ensure the sliding stability of the V-shaped guide and the synchronous pushing of the locking pin.
[0014] Preferably, the upper part of the locking pin hole is connected to a guide coordination hole, and its upper inner wall is set with an inclined surface.
[0015] The guide coordination hole allows the locking pin to be inserted into the guide coordination hole when it is not fully aligned with the locking pin hole and is offset. The pin is then gradually guided into the locking pin hole along its slope, improving the reliability and convenience of the height adjustment of the support leg.
[0016] Preferably, a placement tray is provided between the two crossbeams, one end of which is rotatably hinged to one of the crossbeams, and the middle of both sides of which are hinged to the other crossbeam through two linkage support rods. The placement tray also has a flip handle that facilitates its rotation.
[0017] In the above setup, the tray can be used to place tools and parts, facilitating woodworking. It also connects to the support legs on both sides, improving support stability. The rotating hinge between the tray and the crossbeam allows it to be unfolded or folded along with the support legs.
[0018] Preferably, a lifting limit structure is provided between the support leg and the stabilizing connecting sleeve, which includes a longitudinally opened slide groove in the lifting leg and a limiting protrusion provided in the stabilizing connecting sleeve. The limiting protrusion passes through the slide groove, and the range of the slide groove corresponds to the range of multiple locking pin holes on the support leg.
[0019] The above-mentioned design limits the vertical movement of the lifting rod, preventing it from being accidentally pulled out of the slide rail when sliding.
[0020] Preferably, the outer wall of the lifting leg is marked with a scale value corresponding to each locking pin hole, and the stabilizing connecting sleeve has an observation hole that exposes the scale value so that the user can easily understand the height of the support leg.
[0021] Because the observation hole and the locking pin are a certain distance apart, and in order to allow users to directly read the height of the support legs, the scale value is marked with a certain distance between the corresponding scale value and the locking pin hole.
[0022] Preferably, the upper end of the support beam is provided with a placement groove parallel to its length direction. This is suitable for processing short wooden blocks, where the short wooden block is placed into the placement groove and fixed with self-tapping screws before proceeding with the work.
[0023] Preferably, the upper end of the support beam is provided with two sets of placement notches parallel to its width direction. Two saws can be placed side by side, so that the two sets of placement notches correspond one-to-one and long wooden blocks are inserted to form a support plane. Then, a tabletop is placed on the support plane to form a workbench.
[0024] The beneficial effects of this utility model are as follows: This invention enables the saw to be unfolded and folded for storage by hinged connection between the support legs and the support beam; by setting up a lifting rod with vertical sliding connection and a locking component, the height of the support frame of this saw is adjustable and can be stably locked after adjustment, making it convenient for users of different heights to use, or allowing for height adjustment to meet different work requirements, thus improving the ease of use of this saw.
[0025] This utility model, by setting up a plug-in push-press structure, can control the locking pins on both sides to simultaneously disengage or insert into the locking pin holes, which simplifies operation and improves ease of use. Furthermore, by exposing the lifting switch that controls its start-up in the external space below the crossbeam, the operating space is increased, further improving ease of use.
[0026] This invention also provides an extended guide and coordination hole for the locking pin hole, so that when the locking pin is not fully aligned with the locking pin hole and is offset, it can be inserted into the guide and coordination hole and gradually guided into the locking pin hole along its slope, thereby improving the reliability and convenience of the height adjustment of the support leg. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the structure of the support frame of this utility model after its height has been extended; Figure 2 This is a schematic diagram of the structure of this utility model after folding; Figure 3 This is a cross-sectional view of the present invention in a locked state, with the arrow indicating the process of unlocking. Figure 4 This is a cross-sectional view of the present invention in the unlocked state, with the arrow indicating the process of relocking. Figure 5 for Figure 4 A magnified view of a section at point I; Figure 6 This is a schematic diagram of the lifting rod structure in this utility model; Figure 7 for Figure 1 Enlarged view of a section at point II; Figure 8 This is a schematic diagram of the structure of the single saw horse combined with the short wooden block in this utility model; Figure 9 This is a schematic diagram of the structure of the double saw horse combined with the long wooden block and the table panel in this utility model.
[0028] Figure label: Support beam 10, support leg 20, placement groove 11, placement notch 12, support rod 21, connecting plate frame 22, fixed foot sleeve 211, lifting rod 212, stabilizing connecting sleeve 213, slide rail 2110, cross frame plate 30, locking assembly 40, locking pin hole 41, locking pin 42, plug-in push structure 43, guide coordination hole 411, plug-in push part 431, V-shaped guide part 432, lifting switch 433, restoring spring 434, inclined guide hole 435, first guide inclined surface 4321, second guide inclined surface 4351, guide limiting structure 50, directional slide rod 51, limiting protruding hook 52, longitudinal guide groove 53, limiting boss 54, placement tray 60, linkage support rod 61, flip handle 62, lifting limiting structure 70, slide groove 71, limiting protruding shaft 72, scale value 81, observation hole 82. Detailed Implementation
[0029] Example
[0030] refer to Figure 1 This embodiment provides a height-adjustable saw, including a support beam 10 and two paired support legs 20 located at the lower end of the support beam. The two support legs 20 are rotatably hinged to the support beam 10 via a pivot, allowing the two support legs 20 to unfold relative to the support beam 10 (e.g., Figure 1 (as shown) or folded (as shown) Figure 2 (As shown). Reference Figure 1 , Figure 7 Each set of support legs 20 includes two support legs 21 and a connecting plate frame 22 connecting the two support legs 21 to the support beam 10. Each support leg 21 includes a fixed foot sleeve 211, a lifting leg 212, and a stabilizing connecting sleeve 213 fixedly fitted to the lower end of the fixed foot sleeve 211. The lifting leg 212 passes through the stabilizing connecting sleeve 213 and slides within the slide rail 2110 of the fixed foot sleeve 211. A cross plate 30 is provided between the two stabilizing connecting sleeves 213 of each set of support legs 20 to improve the support stability of each set of support legs 20. (Reference) Figure 1 Each side of the crossbeam 30 is fitted with a locking component 40 between it and the support leg 20.
[0031] refer to Figures 3-5 Specifically, the locking components 40 are symmetrically arranged and used to control the stable connection or disengagement of the crossbeam 30 and the lifting rod 212, and include: Multiple locking pin holes 41 are distributed along the length of the lifting rod 212 (and can be combined) Figure 6 refer to); Two sets of locking pins 42 serve as the direct actuators for locking the locking assembly 40, and can be detachably inserted into the locking pin holes 41 of the lifting foot rods 212 on both sides. The plug-in push structure 43 is movably connected to the cross plate 30 and is used to drive the two locking pins 42 to disengage from the locking pin hole 41 at the same time, or to push the two locking pins 42 into the locking pin hole 41 at the same time to achieve locking.
[0032] Further, refer to Figures 3-5 The insertion and pushing structure 43 includes: Two push-fitting parts 431 are respectively connected to two sets of locking pins 42, serving as pushers to drive the locking pins 42 into or out of the locking pin holes 41; The V-shaped guide 432 is symmetrically arranged and has two first guide ramps 4321. The longitudinal movement of the V-shaped guide 432 is converted into a lateral push on the two plug-in pushers 431 through the two first guide ramps 4321. The lifting switch 433, as a driving component that controls the disengagement of the locking pin 42 from the locking pin hole 41, abuts against the lower end of the V-shaped guide 432, is movably connected to the cross plate 30, and is exposed in the external space below the cross plate 30. The restoring spring 434 is located between the two plug-in pushers 431. Its elastic force is set laterally. When the lifting switch 433 is released, the locking pin 42 can be pushed into the locking pin hole 41 by the elastic force to re-lock.
[0033] To ensure that the upward movement of the V-shaped guide 432 can be converted into the lateral movement of the insertion and pressing member 431, and that the lateral movement of the insertion and pressing member 431 can be converted into the downward movement of the V-shaped guide 432, the insertion and pressing member 431 is provided with a sloping guide hole 435 having a second guide slope 4351. During the up-and-down movement, the V-shaped guide 432 gradually inserts into the sloping guide hole 435, and the first guide slope 4321 abuts against the second guide slope 4351 with the contact area changing accordingly.
[0034] The unlocking and locking processes of the aforementioned locking component 40 are as follows: By default, locking component 40 is in a locked state (e.g., Figure 3 As shown), when adjusting the height of the support leg 20, refer to... Figure 3 , Figure 5The lifting switch 433 can be pressed upward to push the V-shaped guide 432 upward. During the upward movement of the V-shaped guide 432, the two first guide slopes 4321 on it gradually come into complete contact with the second guide slopes 4351 of the two plug-in pushers 431. Through the two slopes that gradually come into complete contact, the V-shaped guide 432 squeezes the two plug-in pushers 431 to move towards the middle, thereby driving the locking pins 42 on both sides to disengage from the locking pin holes 41. At the same time, the two plug-in pushers 431 also compress the restoring spring 434. Then move the lifting rod 212 and adjust the support bracket 20 to the desired height. Once adjustment is complete, refer to... Figure 4 Release the lifting switch 433, and use the spring force of the restoring spring 434 on the two plug-in pushers 431 to push the two plug-in pushers 431 to move outward respectively, thereby pushing the locking pin 42 to re-insert into the locking pin hole 41 to achieve locking. At the same time, the plug-in pushers 431 also push the V-shaped guide 432 down through the two inclined surfaces, and the V-shaped guide 432 then pushes the lifting switch 433 down to return to the initial state.
[0035] To ensure stable longitudinal movement of the V-shaped guide 432 and prevent it from shifting, synchronous pushing of the locking pins 42 on both sides is guaranteed. (Reference) Figure 5 The V-shaped guide member 432 is further provided with a guide limiting structure 50, which includes a directional slide rod 51 located in the middle of the V-shaped guide member 432 and limiting protrusions 52 located on both sides, wherein: The directional slide bar 51 is slidably inserted into the longitudinal guide groove 53 of the cross frame plate 30 (the longitudinal guide groove can be further combined). Figure 3 (Refer to) so that the V-shaped guide 432 can move stably longitudinally, thereby ensuring that the locking pins 42 on both sides can be accurately and synchronously inserted into the locking pin holes 41; The bends of the two limiting protrusions 52 and the end corners of the two limiting bosses 54 on the crossbeam plate 30 can be separated and engaged. When the lifting switch 433 is in the default position, the bends of the limiting protrusions 52 and the end corners of the limiting bosses 54 engage and form a stable limiting effect on the V-shaped guide 432, ensuring that the V-shaped guide 432 is not easily deviated during the up and down movement. Therefore, the first guide slope 4321 on it can stably abut against the second guide slope 4351, which can further ensure the sliding stability of the V-shaped guide 432 and the synchronous pushing of the locking pin 42.
[0036] In this embodiment, reference Figures 3-5 Each set of locking pins 42 has two pins. Therefore, when locking, the two locking pins 42 are inserted into the corresponding two locking pin holes 41, which improves the locking stability of the support leg 20.
[0037] Preferably, refer to Figure 5 , Figure 6The upper part of the locking pin hole 41 is connected to the guide coordination hole 411, and the inner wall of the guide coordination hole 411 is inclined. Therefore, when the locking pin 42 is not fully aligned with the locking pin hole 41 and is offset, it can be inserted into the guide coordination hole 411 and gradually guided into the locking pin hole 41 along its inclined surface, thereby improving the reliability and convenience of the height adjustment of the support leg 20.
[0038] refer to Figure 1 , Figure 2 In this embodiment, a placement tray 60 is provided between the two crossbeams 30, which can be used to place tools and parts, improving ease of use. It also connects the two sets of support legs 20, improving the support stability of the saw. One end of the placement tray 60 is rotatably hinged to one of the crossbeams 30, and the middle of both sides of the placement tray 60 are hinged to the other crossbeam 30 through two linkage support rods 61. The placement tray 60 also has a flip handle 62 for easy rotation.
[0039] When the saw is unfolded, the placement tray 60 can rotate and unfold relative to the crossbeam 30 of the former mentioned above. At the same time, the linkage support rod 61 also rotates and unfolds, and is supported between the crossbeam 30 of the latter mentioned above and the placement tray 60. When the saw is folded and stored, the placement tray 60 and the linkage support rod 61 can rotate and fold together, so that the placement tray 60 can be folded or unfolded together with the saw.
[0040] Furthermore, to limit the vertical movement of the lifting rod 212, and to prevent it from being accidentally pulled out of the slide rail 2110 when sliding, [reference needed]. Figure 5 The support leg 21 and the stable connecting sleeve 213 are further provided with a lifting limit structure 70, which includes a slide groove 71 longitudinally opened in the lifting leg 212 and a limiting protrusion 72 provided in the stable connecting sleeve 213. The limiting protrusion 72 passes through the slide groove 71, and the range of the slide groove 71 corresponds to the range of multiple locking pin holes 41 on the support leg 21.
[0041] refer to Figure 2 , Figure 6 To facilitate users in understanding the height of the support leg 20, the outer wall of the lifting leg 212 is marked with a scale value 81 corresponding to each locking pin hole 41, and the stabilizing connecting sleeve 213 has an observation hole 82 that exposes the scale value 81, so that users can easily understand the height of the support leg 20.
[0042] Furthermore, since there is a certain distance between the observation hole 82 and the locking pin 42, and in order to allow the user to directly read the height of the support leg 20, the scale value 81 is marked with a certain distance between the corresponding scale value 81 and the locking pin hole 41.
[0043] This embodiment has multiple usage methods: One of them is: Reference Figure 1 A placement groove 11 parallel to the length direction is provided at the upper end of the support beam 10. This is suitable for processing shorter wooden blocks. (See reference...) Figure 8 The short wooden block is placed into the placement groove 11 and fixed with self-tapping screws, and then processed.
[0044] The second method is: (refer to) Figure 1 Two sets of placement notches 12, parallel to the width direction, are provided at the upper end of the support beam 10. (Reference) Figure 9 Place the two saws side by side, ensuring that the two sets of placement notches 12 correspond one-to-one. Then, place the two long wooden blocks into the two sets of corresponding placement notches 12 to form a support plane. Finally, place a tabletop on the support plane to form a workbench.
Claims
1. A height-adjustable saw, comprising a support beam (10), and a pair of support legs (20) disposed at the lower end of the support beam, wherein at least one set of support legs (20) is rotatably hinged to the support beam (10), and each set of support legs (20) includes two support rods (21), the support rods (21) including lifting rods (212) that can extend their length by sliding up and down, characterized in that, A crossbeam plate (30) is provided between the two support legs (21) of each group, and a locking assembly (40) is fitted between the crossbeam plate (30) on each side and the support leg (20); the locking assembly (40) is symmetrically arranged and is used to control the stable connection or disengagement of the crossbeam plate (30) and the lifting leg (212), and includes: Multiple locking pin holes (41) are distributed along the length of the lifting rod (212); Two sets of locking pins (42) can be detachably inserted into the locking pin holes (41) of the lifting foot rods (212) on both sides; The plug-in push structure (43) is movably connected to the cross plate (30) and is used to drive the two locking pins (42) to disengage from the locking pin hole (41) at the same time, or to push the two locking pins (42) into the corresponding locking pin hole (41) at the same time to achieve locking.
2. The height-adjustable saw horse according to claim 1, characterized in that, The plug-in push-fit structure (43) includes: Two plug-in pushers (431) are respectively connected to two sets of locking pins (42) and serve as pushers to drive the locking pins (42) to insert into or disengage from the locking pin holes (41); The V-shaped guide (432) is symmetrically arranged and has two first guide ramps (4321). The longitudinal movement of the V-shaped guide (432) is converted into a lateral push on the two plug-in pushers (431) through the two first guide ramps (4321). The lifting switch (433), as a drive component for controlling the disengagement of the locking pin (42) from the locking pin hole (41), abuts against the lower end of the V-shaped guide (432), is movably connected to the cross plate (30), and is exposed below the cross plate (30). The restoring spring (434) is located between the two plug-in pushers (431). Its elastic force is set in the horizontal direction. When the lifting switch (433) is released, the locking pin (42) can be pushed into the locking pin hole (41) by the elastic force to relock.
3. The height-adjustable saw horse according to claim 1, characterized in that, The support leg (21) also includes a fixed foot sleeve (211) and a stabilizing connecting sleeve (213) fixedly sleeved at the lower end of the fixed foot sleeve (211). The lifting leg (212) passes through the stabilizing connecting sleeve (213) and slides in the slide (2110) of the fixed foot sleeve (211). The cross frame plate (30) is connected between the two stabilizing connecting sleeves (213).
4. The height-adjustable saw horse according to claim 2, characterized in that, The insertion push member (431) has a sloping guide hole (435) with a second guide slope (4351). During the up and down movement of the V-shaped guide member (432), the first guide slope (4321) abuts against the second guide slope (4351).
5. The height-adjustable saw horse according to claim 2, characterized in that, The V-shaped guide (432) is also provided with a guide limiting structure (50), which includes a directional slide rod (51) located in the middle of the V-shaped guide (432) and limiting protrusions (52) located on both sides. The directional slide rod (51) is slidably inserted into the longitudinal guide groove (53) of the cross plate (30), and the bends of the two limiting protrusions (52) can be separated from and engaged with the end corners of the two limiting bosses (54) on the cross plate (30).
6. The height-adjustable saw according to any one of claims 1-5, characterized in that, The upper part of the locking pin hole (41) is connected to the guide coordination hole (411), and its upper inner wall is set with an inclined surface.
7. The height-adjustable saw horse according to claim 1, characterized in that, A placement tray (60) is provided between the two crossbeams (30). One end of the tray is rotatably hinged to one of the crossbeams (30), and the middle of both sides is hinged to the other crossbeam (30) through two linkage support rods (61). The placement tray (60) also has a flip handle (62) that facilitates its rotation.
8. The height-adjustable saw horse according to claim 3, characterized in that, A lifting limit structure (70) is also provided between the support leg (21) and the stabilizing connecting sleeve (213), which includes a slide groove (71) longitudinally opened on the lifting leg (212) and a limiting protrusion (72) provided on the stabilizing connecting sleeve (213). The limiting protrusion (72) passes through the slide groove (71), and the range of the slide groove (71) corresponds to the range of multiple locking pin holes (41) on the support leg (21).
9. The height-adjustable saw horse according to claim 3, characterized in that, The outer wall of the lifting foot rod (212) is also marked with a scale value (81) corresponding to each locking pin hole (41), and the stable connecting sleeve (213) is provided with an observation hole (82) that exposes the scale value (81).
10. The height-adjustable saw horse according to claim 1, characterized in that, The upper end of the support beam (10) is provided with a placement groove (11) parallel to its length direction, and also with two sets of placement notches (12) parallel to its width direction.