Semi-permanent-magnet direct-drive electric roller

Abstract

The utility model discloses a semi-permanent magnet direct drive type electric roller, which relates to the technical field of electric rollers, and comprises a structural roller, the middle part of the inner side of the structural roller is rotatably connected with a permanent magnet synchronous motor through a support frame, the output end of the permanent magnet synchronous motor is rotatably connected with two rotating mechanisms, and the two rotating mechanisms are symmetrically distributed left and right; the sides, away from the structural cylinder, of the two rotating mechanisms are rotationally connected with supporting frames, and the lower sides of the two supporting frames are fixedly connected with a supporting plate. According to the semi-permanent magnet direct drive type electric roller, the permanent magnet synchronous motor drives the extension rod to rotate, so that the extension rod drives the ventilation fan blades to rotate, the ventilation fan blades on the two sides are completely consistent in state, and the ventilation fan blades enable external air to enter the structural roller and the extension roller from the outer side in the specific direction; and more electric devices are not added during the period, so that the air-cooled cooling device is more energy-saving and environment-friendly.

Description

Technical Field

[0001] The utility model relates to the technical field of electric rollers, in particular to a semi-permanent magnet direct-drive electric roller. Background Art

[0002] Semi-permanent magnet direct drive electric drum is a new type of electric drum that combines permanent magnet motor and direct drive technology. This electric drum uses a three-phase permanent magnet motor with a planetary gear transmission reducer, which can effectively improve the service life of the gearbox and can achieve a super high power of more than 55KW, showing its strong carrying capacity.

[0003] For example, the Chinese patent publication number CN110868019B discloses an air-cooled outer rotor permanent magnet direct-drive synchronous belt transmission drum motor, which solves the problems that the current permanent magnet direct-drive motor is large in size, is limited by on-site space, and is difficult to install when connected to the belt drum, and the outer rotor permanent magnet synchronous motor uses water and oil for cooling, which is complicated in process and easy to leak or oil and cause motor damage. It includes a motor shaft, and the stator bracket is sleeved on the outside of the motor shaft. Compared with the traditional structure, the invention eliminates the speed reduction device driven by the belt transmission through the arrangement of the motor shaft, stator bracket, stator, rotor, fixing part and motor end cover. The motor is directly used as a drum, which improves the motor efficiency and reduces equipment maintenance; through the cooperation of the air intake fan and the exhaust fan, the wind will pass through the entire motor to bring out the heat. This air-cooled cooling structure makes the motor highly reliable, stable, simple in structure and easy to maintain.

[0004] The existing technology has the following problems:

[0005] The air cooling mechanism on the drum adopts an external air inlet fan and an exhaust fan to allow external cold air to enter the inside of the drum. Compared with ordinary electric drums, this adds additional electrical components and increases power consumption. Utility Model Content

[0006] The utility model provides a semi-permanent magnet direct-drive electric roller to solve the problems raised in the above background technology.

[0007] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0008] A semi-permanent magnet direct-drive electric drum comprises a structural cylinder, wherein the inner middle part of the structural cylinder is rotatably connected to a permanent magnet synchronous motor via a support frame, the output end of the permanent magnet synchronous motor is rotatably connected to a rotating mechanism, and two rotating mechanisms are symmetrically distributed on the left and right, and the two rotating mechanisms are rotatably connected to the support frame on one side away from the structural cylinder, and the lower sides of the two support frames are fixedly connected to support plates, and a plurality of evenly distributed limiting rods are fixedly connected to the left side of the support plate located on the right side near the bottom, and the outer wall of the limiting rod is movably sleeved on the inner side of the bottom wall of the support plate located on the left side.

[0009] Preferably, the rotating mechanism includes a reducer, the input end of the reducer is fixedly connected to the output end of the permanent magnet synchronous motor, the output end of the reducer is fixedly connected to a transmission rod, the outer wall of the transmission rod is fixedly connected to a first gear away from the permanent magnet synchronous motor, the inner side of the inner boss of the structural cylinder is movably sleeved with four annularly distributed screw rods, the left and right ends of the inner wall boss of the structural cylinder are rotatably connected with four annularly distributed rotating seats, the outer wall of the structural cylinder is movably sleeved with an extension cylinder, one end of the screw rod away from the permanent magnet synchronous motor is fixedly connected to the inner side boss of the extension cylinder, the inner side of the rotating seat is threadedly connected to the outer wall of the screw rod, and the outer sides of the four rotating seats are fixedly connected with second gears, and the side of the second gear close to the transmission rod is meshed and connected with the outer side of the first gear.

[0010] Preferably, an extension rod is movably sleeved on the inner side of the transmission rod, and a ventilation fan is fixedly sleeved on the outer wall of the extension rod at a position away from the permanent magnet synchronous motor.

[0011] Preferably, a flange is fixedly sleeved on the inner wall of the extension tube at a position away from the permanent magnet synchronous motor, and the flange is located on the side of the ventilation fan away from the permanent magnet synchronous motor. A filter plate is movably sleeved on the inner side of the extension tube, and the filter plate is located on the side of the flange away from the permanent magnet synchronous motor.

[0012] Preferably, one end of the extension rod away from the permanent magnet synchronous motor is fixedly connected to a fixing component, and the fixing component includes a screw, and one end of the screw close to the reducer is fixedly connected to the end of the extension rod away from the permanent magnet synchronous motor, the outer wall of the screw is threadedly connected to a fixing screw sleeve, the outer wall of the screw is movably sleeved with a fixing frame, and the fixing frame is located on a side of the fixing screw sleeve close to the permanent magnet synchronous motor, the outer wall of the extension tube is fixedly sleeved with a fixing ring on the side away from the permanent magnet synchronous motor, and a plurality of annularly distributed fixing rods are fixedly connected to the edge of one side of the fixing frame close to the permanent magnet synchronous motor, and the outer wall of the fixing rod is movably sleeved in a slot opened on the side of the fixing ring.

[0013] Preferably, a rubber pad is fixedly connected to a side of the fixing frame close to the permanent magnet synchronous motor near the edge, and a side of the rubber pad close to the permanent magnet synchronous motor is tightly attached to a side of the filter plate away from the reducer.

[0014] Preferably, the outer wall of the screw rod is provided with four annularly distributed sliding grooves, and the inner protrusions of the fixing frame are slidably connected to the inner sides of the sliding grooves.

[0015] Preferably, the lower surfaces of the two support plates are rotatably connected to four rectangularly distributed universal wheels near the four corners.

[0016] Due to the adoption of the above technical solution, the utility model has achieved the following technical progress compared with the prior art:

[0017] The utility model provides a semi-permanent magnet direct-drive electric drum, which adopts a permanent magnet synchronous motor, a reducer, a transmission rod, a rubber pad, a ventilation fan blade, a filter plate, an extension tube, an extension rod, a fixing frame and a structural tube. The permanent magnet synchronous motor drives the extension rod to rotate, so that the extension rod drives the ventilation fan blade to rotate. The states of the ventilation fan blades on both sides are completely consistent, so that the ventilation fan blades allow external air to enter the structural tube and the extension tube from the outside along a specific direction, and discharge it from the other side, so as to achieve the purpose of air cooling. During this period, no more electrical components are added, which is more energy-saving and environmentally friendly.

[0018] The utility model provides a semi-permanent magnet direct-drive electric drum, which adopts a structural drum, a permanent magnet synchronous motor, a rotating mechanism, a reducer, a transmission rod, a first gear, a screw rod, a rotating seat, a second gear, an extension drum, an extension rod, a fixing assembly, a screw rod, a fixing screw sleeve, a fixing frame, a fixing rod and a fixing ring. By rotating the fixing screw sleeve, the fixing rod is disengaged from a slot on the fixing ring, so that the extension rod cannot drive the extension drum to rotate. The permanent magnet synchronous motor drives the first gear to rotate, so that the first gear drives the screw rod to rotate. When the screw rod rotates, the extension drum moves laterally along the structural drum, thereby increasing the lateral length of the entire device and improving the applicability of the electric drum. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a three-dimensional structural schematic diagram of the utility model;

[0020] Figure 2 It is a partial cross-sectional three-dimensional structural schematic diagram of the utility model;

[0021] Figure 3 It is a partial cross-sectional three-dimensional structural schematic diagram of the rotating mechanism of the utility model;

[0022] Figure 4 For this utility model Figure 3 A schematic diagram of the enlarged structure of the upper A part;

[0023] Figure 5 It is a partial cross-sectional three-dimensional structural schematic diagram of the extension rod portion of the utility model;

[0024] Figure 6 It is a three-dimensional structural schematic diagram of the fixing component part of the utility model.

[0025] In the figure: 1. structural tube; 2. permanent magnet synchronous motor; 3. rotating mechanism; 31. reducer; 32. transmission rod; 33. first gear; 34. lead screw; 35. rotating seat; 36. second gear; 37. extension tube; 38. extension rod; 39. fixing assembly; 391. screw; 392. fixing screw sleeve; 393. fixing frame; 394. fixing rod; 395. rubber pad; 310. ventilation fan; 311. filter plate; 312. fixing ring; 4. support frame; 5. support plate; 6. limiting rod. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific implementation methods.

[0027] like Figure 1 , Figure 2 As shown, a semi-permanent magnet direct-drive electric drum comprises a structural cylinder 1, the inner middle part of the structural cylinder 1 is rotatably connected to a permanent magnet synchronous motor 2 through a support frame, the output end of the permanent magnet synchronous motor 2 is rotatably connected to a rotating mechanism 3, and two rotating mechanisms 3 are symmetrically distributed on the left and right, and the two rotating mechanisms 3 are rotatably connected to a support frame 4 on the side away from the structural cylinder 1, and the lower sides of the two support frames 4 are fixedly connected to support plates 5, and a plurality of evenly distributed limiting rods 6 are fixedly connected to the left side of the support plate 5 on the right side near the bottom, and the outer wall of the limiting rod 6 is movably sleeved on the inner side of the bottom wall of the support plate 5 on the left side.

[0028] It should be noted that a rotating frame is fixedly connected to the upper side of the support plate 5 away from the support frame 4 , so as to support an end of the extension tube 37 away from the support frame 4 .

[0029] like Figure 3 , Figure 4As shown, the rotating mechanism 3 includes a reducer 31, the input end of the reducer 31 is fixedly connected to the output end of the permanent magnet synchronous motor 2, the output end of the reducer 31 is fixedly connected to a transmission rod 32, the outer wall of the transmission rod 32 is fixedly connected to a position away from the permanent magnet synchronous motor 2, the inner side of the inner boss of the structural cylinder 1 is movably sleeved with four annularly distributed screw rods 34, the left and right ends of the inner wall boss of the structural cylinder 1 are rotatably connected with four annularly distributed rotating seats 35, the outer wall of the structural cylinder 1 is movably sleeved with an extension cylinder 37, one end of the screw rod 34 away from the permanent magnet synchronous motor 2 is fixedly connected to the inner side boss of the extension cylinder 37, the inner side of the rotating seat 35 is threadedly connected to the outer wall of the screw rod 34, and the outer sides of the four rotating seats 35 are fixedly connected with second gears 36, and the side of the second gear 36 close to the transmission rod 32 is meshed and connected with the outer side of the first gear 33.

[0030] It should be noted that the permanent magnet synchronous motor 2 drives the internal components of the reducer 31 to rotate. The reducer 31 is used to reduce the rotation speed of the permanent magnet synchronous motor 2, so that the reducer 31 drives the transmission rod 32 to rotate, and the transmission rod 32 drives the first gear 33 to rotate. When the first gear 33 rotates, it drives the second gear 36 to rotate. The rotation of the second gear 36 drives the rotating seat 35 to rotate. The rotation of the rotating seat 35 drives the screw rod 34 to move horizontally, causing the screw rod 34 to drive the extension tube 37 to move horizontally.

[0031] like Figure 3 , Figure 5 As shown, an extension rod 38 is movably sleeved on the inner side of the transmission rod 32 , and a ventilation fan fin 310 is fixedly sleeved on the outer wall of the extension rod 38 at a position away from the permanent magnet synchronous motor 2 .

[0032] It should be noted that when the transmission rod 32 rotates, the extension rod 38 is driven to rotate, and when the extension rod 38 rotates, the ventilation blades 310 are driven to rotate. The two ventilation blades 310 on the left and right sides are in the same state and shape, so that the wind direction is consistent when the ventilation blades 310 rotate.

[0033] like Figure 3 , Figure 5 As shown, a flange is fixedly sleeved on the inner wall of the extension tube 37 at a position away from the permanent magnet synchronous motor 2, and the flange is located on the side of the ventilation fan 310 away from the permanent magnet synchronous motor 2, and a filter plate 311 is movably sleeved on the inner side of the extension tube 37, and the filter plate 311 is located on the side of the flange away from the permanent magnet synchronous motor 2.

[0034] It should be noted that the filter plate 311 is used to filter dust in the air passing through it to prevent the dust from affecting the operation of internal devices or increasing the wear of the internal devices.

[0035] like Figure 3 , Figure 5 and Figure 6As shown, one end of the extension rod 38 away from the permanent magnet synchronous motor 2 is fixedly connected to a fixing assembly 39, and the fixing assembly 39 includes a screw 391, and one end of the screw 391 close to the reducer 31 is fixedly connected to the end of the extension rod 38 away from the permanent magnet synchronous motor 2, and the outer wall of the screw 391 is threadedly connected to a fixing screw sleeve 392, and the outer wall of the screw 391 is movably sleeved with a fixing frame 393, and the fixing frame 393 is located on a side of the fixing screw sleeve 392 close to the permanent magnet synchronous motor 2, and the outer wall of the extension tube 37 is fixedly sleeved with a fixing ring 312 on the side away from the permanent magnet synchronous motor 2, and a plurality of annularly distributed fixing rods 394 are fixedly connected at the edge of one side of the fixing frame 393 close to the permanent magnet synchronous motor 2, and the outer wall of the fixing rod 394 is movably sleeved in a slot opened on the side of the fixing ring 312.

[0036] It should be noted that the end of the screw 391 away from the permanent magnet synchronous motor 2 is rotatably connected to the side of the support frame 4 close to the reducer 31, and the fixing screw sleeve 392 is used to fix the fixing frame 393, so that the fixing frame 393 is close to the side of the extension tube 37 away from the permanent magnet synchronous motor 2. At the same time, the fixing rod 394 is fixed in the slot on the fixing ring 312 so that when the extension rod 38 rotates, it drives the fixing frame 393 to rotate, and when the fixing frame 393 rotates, it drives the fixing rod 394 to rotate, and the fixing rod 394 drives the extension tube 37 to rotate. The extension tube 37 relies on the internal screw rod 34 to drive the structural tube 1 to rotate. At this time, the extension tube 37, the structural tube 1 and the first gear 33 rotate synchronously, so that the first gear 33 cannot drive the second gear 36 to rotate, and the fixing screw sleeve 392 is rotated to move the fixing screw sleeve 392 to the side close to the support frame 4, so that the fixing rod 394 is separated from the fixing ring 312, so that the extension rod 38 cannot drive the extension tube 37 to rotate, and the first gear 33 can drive the second gear 36 to rotate.

[0037] like Figure 5 As shown, a rubber pad 395 is fixedly connected to a side of the fixing frame 393 close to the permanent magnet synchronous motor 2 near the edge, and a side of the rubber pad 395 close to the permanent magnet synchronous motor 2 is tightly attached to a side of the filter plate 311 away from the reducer 31 .

[0038] It should be noted that the rubber pad 395 fixes the filter plate 311 to prevent the filter plate 311 from moving inside the extension tube 37 .

[0039] like Figure 6 As shown, the outer wall of the screw rod 391 is provided with four annularly distributed sliding grooves, and the inner protrusions of the fixing frame 393 are slidably connected to the inner sides of the sliding grooves.

[0040] It should be noted that the slide groove is used to fix the fixing frame 393, so that when the extension rod 38 rotates, the fixing frame 393 will rotate along with the extension rod 38, and at the same time, it can prevent the fixing rod 394 from deviating from the slot on the fixing ring 312.

[0041] like Figure 1 As shown, the lower surfaces of the two support plates 5 near the four corners are rotatably connected with four universal wheels distributed in a rectangular shape.

[0042] It should be noted that when the extension tube 37 moves, the support frame 4 will also move to the side away from each other. At this time, the support frame 4 will drive the support plate 5 to move, and the universal wheel is used to reduce the friction between the support plate 5 and the bottom surface.

[0043] The working principle of the utility model is as follows: first, the permanent magnet synchronous motor 2 drives the internal components of the reducer 31 to rotate. The reducer 31 is used to reduce the speed of the permanent magnet synchronous motor 2, so that the reducer 31 drives the transmission rod 32 to rotate. When the transmission rod 32 rotates, it drives the extension rod 38 to rotate. When the extension rod 38 rotates, it drives the ventilation fan blades 310 to rotate. The two ventilation fan blades 310 on the left and right sides are in the same state and shape, so that the wind direction of the ventilation fan blades 310 is consistent when the ventilation fan blades 310 rotate. The filter plate 311 is used to filter dust in the air passing through it to prevent dust from affecting the operation of the internal components or increasing the wear of the internal components. The rubber pad 395 fixes the filter plate 311 to prevent the filter plate 311 from moving on the inner side of the extension tube 37. The extension rod 38 rotates, causing the extension rod 38 to drive the ventilation blades 310 to rotate. The states of the ventilation blades 310 on both sides are completely consistent, causing the ventilation blades 310 to allow external air to enter the structural tube 1 and the extension tube 37 from the outside along a specific direction, and discharge it from the other side, thereby achieving the purpose of air cooling. During this period, no more electrical components are added, which is more energy-saving and environmentally friendly. Finally, the end of the screw 391 away from the permanent magnet synchronous motor 2 is rotated and connected to the side of the support frame 4 close to the reducer 31. The fixing screw sleeve 392 is used to fix the fixing frame 393, so that the fixing frame 393 is close to the side of the extension tube 37 away from the permanent magnet synchronous motor 2. At the same time, the fixing rod 394 is fixed in the slot on the fixing ring 312 so that when the extension rod 38 rotates, The movable fixing frame 393 rotates, and when the fixing frame 393 rotates, the fixing rod 394 is driven to rotate, and the fixing rod 394 drives the extension tube 37 to rotate. The extension tube 37 relies on the internal screw rod 34 to drive the structure tube 1 to rotate. At this time, the extension tube 37, the structure tube 1 and the first gear 33 rotate synchronously, so that the first gear 33 cannot drive the second gear 36 to rotate, and the fixed screw sleeve 392 is rotated to make the fixed screw sleeve 392 move to the side close to the support frame 4, so that the fixing rod 394 is separated from the fixing ring 312, so that the extension rod 38 cannot drive the extension tube 37 to rotate. At this time, the first gear 33 can drive the second gear 36 to rotate, and the permanent magnet synchronous motor 2 drives the internal components of the reducer 31 to rotate. The reducer 31 is used to reduce the speed of the permanent magnet synchronous motor 2, resulting in The reducer 31 drives the transmission rod 32 to rotate, the transmission rod 32 drives the first gear 33 to rotate, and the first gear 33 drives the second gear 36 to rotate when it rotates. The rotation of the second gear 36 drives the rotating seat 35 to rotate, and the rotation of the rotating seat 35 drives the screw rod 34 to move laterally, so that the screw rod 34 drives the extension tube 37 to move laterally, and by rotating the fixed screw sleeve 392, the fixed rod 394 is disengaged from the slot on the fixed ring 312, so that the extension rod 38 cannot drive the extension tube 37 to rotate, and the permanent magnet synchronous motor 2 drives the first gear 33 to rotate, so that the first gear 33 drives the screw rod 34 to rotate, and when the screw rod 34 rotates, the extension tube 37 moves laterally along the structural tube 1, thereby increasing the lateral length of the entire device and improving the applicability of the electric drum.

[0044] The above shows and describes the basic principle and main features of the utility model and the advantages of the utility model. Those skilled in the art should understand that the utility model is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principle of the utility model. Without departing from the spirit and scope of the utility model, the utility model may have various changes and improvements, which fall within the scope of the utility model to be protected. The scope of protection claimed by the utility model is defined by the attached claims and their equivalents.

Claims

1. A semi-permanent magnet direct-drive electric drum, comprising a structural drum (1), characterized in that: A permanent magnet synchronous motor (2) is rotatably connected to the middle part of the inner side of the structural tube (1) via a support frame, an output end of the permanent magnet synchronous motor (2) is rotatably connected to a rotating mechanism (3), and two rotating mechanisms (3) are symmetrically distributed on the left and right sides, and the two rotating mechanisms (3) are rotatably connected to a supporting frame (4) on the side away from the structural tube (1), and a supporting plate (5) is fixedly connected to the lower side of the two supporting frames (4), and a plurality of uniformly distributed limiting rods (6) are fixedly connected to the left side of the supporting plate (5) located on the right side near the bottom, and the outer wall of the limiting rod (6) is movably sleeved on the inner side of the bottom wall of the supporting plate (5) located on the left side.

2. A semi-permanent magnet direct-drive electric drum according to claim 1, characterized in that: The rotating mechanism (3) comprises a reducer (31), the input end of the reducer (31) being fixedly connected to the output end of the permanent magnet synchronous motor (2), the output end of the reducer (31) being fixedly connected to a transmission rod (32), a first gear (33) being fixedly connected to an outer wall of the transmission rod (32) at a position away from the permanent magnet synchronous motor (2), four annularly distributed screw rods (34) being movably sleeved on the inner side of the inner side boss of the structural tube (1), and four screw rods (34) being rotatably connected to the left and right ends of the inner wall boss of the structural tube (1). The outer wall of the structural cylinder (1) is movably sleeved with an extension cylinder (37); one end of the screw rod (34) away from the permanent magnet synchronous motor (2) is fixedly connected to the inner boss of the extension cylinder (37); the inner side of the rotating seat (35) is threadedly connected to the outer wall of the screw rod (34); the outer sides of the four rotating seats (35) are fixedly connected with a second gear (36); and the side of the second gear (36) close to the transmission rod (32) is meshed and connected with the outer side of the first gear (33).

3. A semi-permanent magnet direct-drive electric drum according to claim 2, characterized in that: An extension rod (38) is movably sleeved on the inner side of the transmission rod (32), and a ventilation fan blade (310) is fixedly sleeved on the outer wall of the extension rod (38) at a position away from the permanent magnet synchronous motor (2).

4. A semi-permanent magnet direct-drive electric drum according to claim 3, characterized in that: A flange is fixedly sleeved on the inner wall of the extension tube (37) at a position away from the permanent magnet synchronous motor (2), and the flange is located on a side of the ventilation fan blades (310) away from the permanent magnet synchronous motor (2), and a filter plate (311) is movably sleeved on the inner side of the extension tube (37), and the filter plate (311) is located on a side of the flange away from the permanent magnet synchronous motor (2).

5. A semi-permanent magnet direct-drive electric drum according to claim 4, characterized in that: The end of the extension rod (38) away from the permanent magnet synchronous motor (2) is fixedly connected to a fixing assembly (39), the fixing assembly (39) comprising a screw rod (391), the end of the screw rod (391) close to the reducer (31) is fixedly connected to the end of the extension rod (38) away from the permanent magnet synchronous motor (2), the outer wall of the screw rod (391) is threadedly connected to a fixing screw sleeve (392), the outer wall of the screw rod (391) is movably sleeved with a fixing frame (393), and the fixing frame (393) is located on a side of the fixing screw sleeve (392) close to the permanent magnet synchronous motor (2), the outer wall of the extension tube (37) is fixedly sleeved with a fixing ring (312) on the side away from the permanent magnet synchronous motor (2), and the edge of one side of the fixing frame (393) close to the permanent magnet synchronous motor (2) is fixedly connected to a plurality of annularly distributed fixing rods (394), and the outer wall of the fixing rod (394) is movably sleeved in a slot opened on the side of the fixing ring (312).

6. A semi-permanent magnet direct-drive electric drum according to claim 5, characterized in that: A rubber pad (395) is fixedly connected to a side of the fixing frame (393) close to the permanent magnet synchronous motor (2) at a position close to the edge, and a side of the rubber pad (395) close to the permanent magnet synchronous motor (2) is tightly attached to a side of the filter plate (311) away from the reducer (31).

7. The semi-permanent magnet direct-drive electric drum according to claim 5, characterized in that: The outer wall of the screw rod (391) is provided with four annularly distributed sliding grooves, and the inner protrusions of the fixing frame (393) are slidably connected to the inner sides of the sliding grooves.

8. The semi-permanent magnet direct-drive electric drum according to claim 1, characterized in that: The lower surfaces of the two support plates (5) are rotatably connected to four rectangularly distributed universal wheels near the four corners.

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