A telescopic ladder

Abstract

The present application relates to a telescopic ladder, including telescopic ladder body, the upper end of telescopic ladder body horizontal pole both ends are penetrated and hinged with protective cover, the protective cover is composed of three frames, each frame includes two side plates and a movable plate movably connected between the two side plates, two side plates are provided with corresponding positioning holes, there is a fixed shaft between the two side plates, there is a movable plate between the two side plates close to the outer edge of the two side plates, the movable plate includes a telescopic rod and two leaf plates, the upper end of the upper leaf plate of the two leaf plates is rotatably connected to the fixed shaft, and the end of the two leaf plates hinged and the lower end of the lower leaf plate of the two leaf plates are movably connected to a set of positioning holes on the two side plates through the telescopic rod. The present application is a telescopic ladder with protection function and convenient maintenance operation, especially suitable for maintenance and repair work of optical cable in mountainous areas.

Description

Technical Field

[0001] This invention relates to the field of optical cable maintenance tools, specifically to a telescopic ladder. Background Technology

[0002] Aerial optical cables are optical cables that are suspended on utility poles. This method of laying aerial optical cables can utilize existing overhead open-wire lines, saving construction costs and shortening the construction period. Aerial optical cables, suspended on utility poles, are required to adapt to various natural environments and are generally used for long-distance Class II or lower lines. They are suitable for dedicated optical cable networks or certain special local sections.

[0003] Overhead optical cables are typically maintained using maintenance vehicles, but these are unsuitable for mountainous areas with poor transportation. Ordinary ladders are heavy and bulky, making them unsuitable for carrying and use in mountainous areas. Telescopic ladders, on the other hand, are lightweight and compact, making them suitable for carrying in mountainous areas and for high-altitude operations. Currently, optical cable maintenance typically uses the telescopic ladder disclosed in the design patent application number 202230124627.3, whose structure is similar to that of an anti-pinch telescopic ladder in application number 201820421159.4. Both include ladder tubes, crossbars between the ladder tubes, and stops on the lower surface of the crossbars; the crossbars and ladder tubes are connected by a locking structure.

[0004] The existing telescopic ladders can only be leaned against the steel strands of the optical cable. When in use, maintenance personnel need to stand on the telescopic ladder to carry out maintenance, which is inconvenient to operate and lacks protection, making accidents very easy to occur. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the present invention provides a telescopic ladder, the purpose of which is to provide a telescopic ladder with protective functions and convenient maintenance operations.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A telescopic ladder includes a telescopic ladder body, which includes multiple sets of ladder tubes. In two adjacent sets of ladder tubes, the upper ladder tube retracts into the lower ladder tube. A crossbar is provided between each set of ladder tubes. The front and rear ends of the crossbar at the top of the telescopic ladder body pass through the front and rear ladder tubes, and a protective cover is hinged between the two ends.

[0008] The protective cover consists of three frames. Each frame includes two side plates and a movable plate movably connected between the two side plates. There is a fixed shaft between the upper ends of the two side plates and a movable plate near the outer edge of the two side plates. The movable plate includes a telescopic rod and two blades hinged together. The upper end of the upper blade is rotatably connected to the fixed shaft. The two blades are hinged together at the hinge point and at the lower end of the lower blade. The two ends of the telescopic rod are movably connected to the two side plates.

[0009] The side plates on the same side of the three frames are on the same vertical plane. The bottom frame is provided with rollers near the outer edge and bottom of the frame. The outer peripheral wall of the rollers makes rolling contact with the ladder tube.

[0010] Furthermore, the blade is a rectangular plate with a through groove recessed into the middle of each of the two long sides of the blade and opening outward. There are hinge tubes on the blades on the front and rear sides of the through groove. A telescopic rod is installed in the hinge tube at the hinge joint of the two blades and in the hinge tube at the lower end of the lower blade of the two blades. The hinge tube at the upper end of the upper blade of the two blades is sleeved on the fixed shaft.

[0011] Furthermore, the two side plates of each frame are symmetrical front and back, and both side plates are fan-shaped plates. Both side plates are rotatably connected to the two ends of the uppermost crossbar through a connecting ring at the center. Each frame has corresponding positioning holes on its two side plates. The positioning holes include a first positioning hole, a second positioning hole, and a third positioning hole. The first positioning hole is located between the fixed shaft and the outer edge of the side plate, the second positioning hole is close to the middle of the outer edge of the side plate, and the third positioning hole is close to the middle of the lower edge of the side plate.

[0012] Furthermore, in each of the two telescopic rods within the frame, the two ends of the upper telescopic rod are movably connected to the two side plates via the second positioning hole, and the two ends of the lower telescopic rod are movably connected to the two side plates via the third positioning hole; or in each of the two telescopic rods within the frame, the two ends of the upper telescopic rod are movably connected to the two side plates via the second positioning hole, and in the two telescopic rods within the frames other than the bottom frame, the two ends of the lower telescopic rod are movably connected to the two adjacent side plates below via the first positioning hole of the adjacent frame below, and the two ends of the lower telescopic rod in the bottom frame are movably connected to the two side plates via the third positioning hole.

[0013] Furthermore, the two side plates of the bottommost frame of the three frames are provided with multiple sets of adjustment holes corresponding to the front and back. Each of the multiple sets of adjustment holes is arranged on a circle with the fixed axis of the side plate as the center and the center distance between the second positioning hole of the side plate and the fixed axis as the radius. The two ends of the telescopic rod located at the top of the bottommost frame can also be movably connected to the two side plates through any set of adjustment holes. When the two ends of the telescopic rod located at the top of the bottommost frame are movably connected to the two side plates through any set of adjustment holes, the two ends of the telescopic rod located at the bottom of the bottommost frame are in contact with the side plate.

[0014] Furthermore, when the two ends of the telescopic rod located at the top in the bottom frame are movably connected to the two side plates via one of the sets of adjustment holes, and the center distance between this set of adjustment holes and the second positioning hole on the side plate is equal to the center distance between the two telescopic rods on the movable plate, the two ends of the telescopic rod located at the bottom in the bottom frame are movably connected to the two side plates via the second positioning hole.

[0015] Furthermore, the telescopic rod includes a sleeve, two sliding rods, and a compression spring. The sleeve is inserted into the hinge tube and slides in contact with the hinge tube. The sleeve has a through hole in the middle of its peripheral wall that corresponds to the through groove on the blade. Sliding rods that slide in contact with the inner peripheral wall of the sleeve are provided in the front and rear parts of the sleeve. A lever extending out of the through hole is provided on the outer peripheral wall of the opposite ends of the two sliding rods. The other ends of the two sliding rods extend out of the sleeve. A compression spring located inside the sleeve is provided between the opposite ends of the two sliding rods through the corresponding through hole.

[0016] Furthermore, the upper ends of the two ladder tubes of the uppermost set of ladder tubes of the telescopic ladder body are each connected to a hook with its free end away from the protective cover. The hook is an n-shaped rod body formed by connecting two straight rods and an arc-shaped rod in sequence. The two straight rods of the hook are provided with corresponding through holes. A clamping plate is hinged in the through hole of one of the straight rods. The clamping plate is a fan-shaped plate body. The center of the clamping plate is hinged to the upper end of the through hole. The free end of the hook is provided with a threaded hole that passes through the free end of the hook and connects to the through hole. A bolt is connected in the threaded hole. The bolt passes through the threaded hole and presses against the outer peripheral wall of the clamping plate.

[0017] Furthermore, the outer peripheral wall of the clamping plate is provided with serrations that are inclined toward the free end of the hook. The end face where the upper end of the outer peripheral wall of the clamping plate is connected to the center of the circle is the working surface of the clamping plate. The working surface of the clamping plate is provided with a downwardly recessed semi-circular notch with an upward opening.

[0018] Furthermore, the two lower ends of the two ladder tubes in the lowest set of ladder tubes of the telescopic ladder body are connected to cones with their tips pointing downwards. Each of the two ladder tubes in the lowest set of ladder tubes of the telescopic ladder body is connected to a support rod on the same side as the free end of the hook. The right end of the support rod is connected to the ladder tube, and the left end is rotatably connected to a roller.

[0019] The beneficial effects of the present invention through the above technical solution are as follows:

[0020] This invention ensures the stability of the telescopic ladder even during maintenance and repair, despite the large movements of maintenance personnel. This invention is both convenient for maintenance operations and has a protective function.

[0021] The protective cover of this invention serves not only as a protective cover during maintenance and repair processes to protect maintenance personnel, but also as a support platform for supporting maintenance equipment and materials.

[0022] This invention can also be used as a transport vehicle on the way to maintenance and repair, with a protective cover to protect equipment and materials, reducing the burden on maintenance personnel. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention;

[0024] Figure 2 This is the front view of the present invention (the lower part of the telescopic ladder body is omitted).

[0025] Figure 3 This is a schematic diagram of the structure of the protective cover of the present invention;

[0026] Figure 4 This is a cross-sectional front view of the protective cover of the present invention;

[0027] Figure 5 This is a schematic diagram (partial cross-sectional view) of the hook structure of the present invention.

[0028] Figure 6 This is a schematic diagram of the connection between the blade and the telescopic rod of the present invention;

[0029] Figure 7 This is a schematic diagram of the telescopic rod of the present invention;

[0030] Figure 8 This is a diagram (partial cross-section) showing the usage status of the present invention during the maintenance process.

[0031] Figure 9 This is a diagram (partial cross-section) showing the usage of the present invention as a transport trolley.

[0032] The attached diagram is labeled as follows: 1. Ladder tube; 2. Crossbar; 3. Frame; 4. Side plate; 5. Movable plate; 6. Connecting ring; 7. Positioning hole; 8. Fixed shaft; 9. Leaf plate; 10. Telescopic rod; 11. Roller; 12. Through groove; 13. Hinge tube; 14. Sleeve; 15. Sliding rod; 16. Through hole; 17. Lever; 18. Compression spring; 19. First positioning hole; 20. Second positioning hole; 21. Third positioning hole; 22. Adjustment hole; 23. Hook; 24. Through hole; 25. Clamping plate; 26. Bolt; 27. Serrated edge; 28. Cone; 29. ​​Support rod; 30. Roller. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0034] It should be noted that the directional terms "front", "back", "left", "right", "up", "down", "bottom", and "top" used in the following description refer to the directions shown in the attached diagram, while the terms "inside" and "outside" refer to the directions toward or away from the geometric center of a specific component, respectively.

[0035] like Figures 1-9 As shown, a telescopic ladder includes a telescopic ladder body, which includes multiple sets of ladder tubes 1. In two adjacent sets of ladder tubes, the upper ladder tube retracts into the lower ladder tube. A crossbar 2 is provided between each set of ladder tubes 1. The crossbar 2 and the ladder tube 1 are connected by a locking structure. The front and rear ends of the uppermost crossbar 2 of the telescopic ladder body pass through the front and rear ladder tubes 1, and a protective cover located on the right side of the telescopic ladder body is hinged between the two ends.

[0036] The protective cover consists of three frames 3. Each frame 3 includes two side plates 4 and a movable plate 5 movably connected between the two side plates 4. There is a fixed shaft 8 between the upper ends of the two side plates 4. The fixed shaft 8 is a round rod. The fixed shaft 8 is close to the intersection of the upper edge of the side plate 4 and the outer edge of the side plate 4. The two ends of the fixed shaft 8 are fixedly connected to the opposite sides of the two side plates 4. There is a movable plate 5 between the two side plates 4, close to the outer edge of the two side plates 4. The movable plate 5 includes a telescopic rod 10 and two blades 9 that are hinged together. The upper end of the upper blade 9 is rotatably connected to the fixed shaft 8. The telescopic rod 10 is hinged at the hinge point of the two blades 9 and at the lower end of the lower blade 9. The two ends of the telescopic rod 10 are movably connected to the two side plates 4.

[0037] The side plates 4 on the same side of the three frames 3 are on the same vertical plane. The bottom frame 3 is provided with a roller 11 near the outer edge and the bottom of the frame 3. The roller 11 is a cylinder. The two ends of the roller 11 are respectively rotatably connected to the two side plates 4 of the bottom frame 3. The outer peripheral wall of the roller 11 is in rolling contact with the ladder tube 1. The roller 11 can limit the position of the protective cover.

[0038] The blade 9 is a rectangular plate, and the length of the blade 9 corresponds to the distance between the two side plates 4. There is a through groove 12 in the middle of the two long sides of the blade 9, which is recessed into the blade 9 and opens outward. There are hinge tubes 13 on the blade 9 on the front and rear sides of the through groove 12. The hinge tube 13 is a round tube connected to one end of the long side of the blade 9. The hinge tubes 13 of two adjacent blades 9 are staggered front and rear. A telescopic rod 10 is installed in the hinge tube 13 at the hinge joint of the two blades 9 and in the hinge tube 13 at the lower end of the lower blade 9. The hinge tube 13 at the upper end of the upper blade 9 is sleeved on the fixed shaft 8.

[0039] Each frame 3 has two symmetrical side plates 4, each fan-shaped. A connecting ring 6 is located at the center of each side plate 4. The arc-shaped edge of each side plate 4 forms its outer edge. The line connecting the upper end of the outer edge of each side plate 4 to its center forms its upper edge, and the line connecting the lower end of its outer edge to its center forms its lower edge. Both side plates 4 are rotatably connected to the two ends of the uppermost crossbar 2 via the connecting ring 6 at their centers. Each frame 3 has two corresponding positioning holes 7 on its two side plates 4. The positioning holes 7 include a first positioning hole 19, a second positioning hole 20, and a third positioning hole 21. The diameters of the second positioning hole 20 and the third positioning hole 21 are equal. The first positioning hole 19 is located between the fixed shaft 8 and the outer edge of the side plate 4. The second positioning hole 20 is close to the middle of the outer edge of the side plate 4, and the third positioning hole 21 is close to the middle of the lower edge of the side plate 4. The center distance between the fixed shaft 8 and the second positioning hole 20, and the center distance between the second positioning hole 20 and the third positioning hole 21 are both equal to the center distance between the hinge tubes at the upper and lower ends of the blade plate 9. When two adjacent frames 3 are in contact, the center distance between the second positioning hole 20 of the upper frame 3 and the first positioning hole 19 of the lower adjacent frame 3 is equal to the center distance between the hinge tubes at the upper and lower ends of the blade plate 9. The position of the positioning hole 7 is preferred.

[0040] The sum of the widths of the two blades 9 is greater than the arc length of the arc edge of the side plate 4. In each frame 3, the two ends of the upper telescopic rod 10 are movably connected to the two side plates 4 via the second positioning hole 20, and the two ends of the lower telescopic rod 10 are movably connected to the two side plates 4 via the third positioning hole 21; or in each frame 3, the two ends of the upper telescopic rod 10 are movably connected to the two side plates 4 via the second positioning hole 20. In the other frames except the bottom frame, the two ends of the lower telescopic rod 10 are movably connected to the two adjacent side plates 4 below via the first positioning hole 19 of the adjacent frame below, and the two ends of the lower telescopic rod 10 in the bottom frame are movably connected to the two side plates 4 below via the third positioning hole 21.

[0041] The two side plates 4 of the bottommost frame 3 of the three frames 3 are provided with multiple sets of adjustment holes 22 corresponding to each other. The diameter of each adjustment hole 22 is equal to the diameter of the positioning hole 7. Each adjustment hole 22 is arranged on a circle with the fixed shaft 8 of the side plate 4 as the center and the center distance between the second positioning hole 20 of the side plate 4 and the fixed shaft 8 as the radius. The two ends of the telescopic rod 10 located at the top of the bottommost frame can also be movably connected to the two side plates 4 through any set of adjustment holes 22. When the two ends of the telescopic rod 10 located at the top of the bottommost frame are movably connected to the two side plates 4 through any set of adjustment holes 22, the two ends of the telescopic rod 10 located at the bottom of the bottommost frame are in contact with the side plate 4.

[0042] When the two ends of the telescopic rod 10 located at the top in the bottommost frame are movably connected to the two side plates 4 via one set of adjustment holes 22, and the center distance between this set of adjustment holes 22 and the second positioning hole 20 on the side plate 4 is equal to the center distance between the two telescopic rods 10 on the movable plate 5, the two ends of the telescopic rod 10 located at the bottom in the bottommost frame are movably connected to the two side plates 4 via the second positioning hole 20.

[0043] The telescopic rod 10 includes a sleeve 14, two sliding rods 15, and a compression spring 18. The sleeve 14 is a cylindrical tube that passes through and slides in contact with the hinge tube 13. A through hole 16, corresponding to the through groove 12 on the blade plate 9, is provided in the middle of the sleeve 14's peripheral wall. The through hole 16 is a strip-shaped hole along the length of the sleeve 14 and communicates with the interior of the sleeve 14. Sliding rods 15, sliding in contact with the inner peripheral wall of the sleeve 14, are provided at both the front and rear parts of the sleeve 14. The diameter of the sliding rods 15 matches the diameter of the positioning hole 7. A lever 17, a cylindrical rod, extends out of the through hole 16 from the outer peripheral wall of the opposite ends of the two sliding rods 15. The other end of each slide rod extends out of the sleeve 14. The end of the slide rod 15 extending out of the sleeve 14 is the free end of the telescopic rod 10. A compression spring 18 is provided in the sleeve 14 between the opposite ends of the two slide rods 15 through the corresponding hole 16. By moving the lever 17 of the two slide rods 15 to bring them closer together, the connection between the telescopic rod 10 and the positioning hole 7 or the adjustment hole 22 can be canceled, causing the movable plate 5 to move. When the telescopic rod 10 is coaxial with other positioning holes 7 or adjustment holes 22, the lever 17 can be released to allow the free end of the telescopic rod 10 to extend into the positioning hole 7 or the adjustment hole 22, thus connecting the telescopic rod 10 with the positioning hole 7 or the adjustment hole 22. The telescopic rod 10 can not only act as a hinge but also as a switch.

[0044] The uppermost set of ladder tubes 1 of the telescopic ladder body has hooks 23 connected to the upper ends of both ladder tubes 1, with the free ends away from the protective cover. Each hook 23 is an n-shaped rod consisting of two straight rods and an arc-shaped rod connected in sequence. The lower end of one straight rod is fixedly connected to the upper end of the ladder tube 1, and the lower end of the other straight rod is the free end of the hook 23. The two straight rods of the hook 23 have corresponding through holes 24. Each through hole 24 is a rectangular through hole, with the straight rods of the hook 23 passing through both ends. A clamping plate 25 is hinged inside the through hole 24 of one of the straight rods. The clamping plate 25 is a fan-shaped plate with a radius greater than the distance between the two straight rods and less than the distance between the upper and lower ends of the through hole 24. The center of the clamping plate 25 is aligned with the through hole 24. The upper end of the through hole 24 is hinged, and the curved surface where the arc edge of the clamping plate 25 is located is the outer peripheral wall of the clamping plate 25. The free end of the hook 23 is provided with a threaded hole that passes through the free end of the hook 23 and connects to the through hole 24. A bolt 26 is connected in the threaded hole. The bolt 26 passes through the threaded hole and tightens against the outer peripheral wall of the clamping plate 25. The hook 23 and the clamping plate 25 clamp the steel strand of the suspended optical cable inside, and exclude the optical cable from the hook 23 for easy maintenance or repair. Since the hook 23 and the clamping plate 25 clamp the steel strand of the suspended optical cable inside, the upper end of the telescopic ladder body is connected to the steel strand. Even if the various actions of the maintenance personnel make the telescopic ladder unstable, the telescopic ladder body and the steel strand can be kept relatively fixed, and there will be no slippage or overturning.

[0045] The outer peripheral wall of the clamping plate 25 is provided with serrations 27 that are inclined toward the free end of the hook 23. The end face where the upper end of the outer peripheral wall of the clamping plate 25 is connected to the center of the circle is the working surface of the clamping plate 25. The working surface of the clamping plate 25 is provided with a downwardly recessed semi-circular notch with an upward opening. The semi-circular notch can accommodate the optical cable, that is, when the hook 23 and the clamping plate 25 clamp the steel strand of the suspended optical cable inside, the optical cable is no longer excluded from the hook 23, but can be accommodated in the semi-circular notch, preventing the working surface of the clamping plate 25 from crushing the optical cable.

[0046] The two lower ends of the two ladder tubes 1 at the bottom of the telescopic ladder body are connected to a cone 28 with its tip pointing downwards, which is used to insert into the ground to prevent the lower end of the telescopic ladder body from moving. Each of the two ladder tubes 1 at the bottom of the telescopic ladder body is connected to a support rod 29 on the same side as the free end of the hook 23. The right end of the support rod 29 is connected to the ladder tube 1, and the left end is rotatably connected to a roller 30. This invention can be used as a transport trolley to transport maintenance equipment and reduce the burden on maintenance personnel on the way to maintenance or repair.

[0047] The side plate 4 of the present invention is made of fiberglass or carbon fiber, and the radius of the side plate 4 is 1 meter, which ensures the protective capability while reducing the weight of the protective cover and does not affect normal use.

[0048] The telescopic ladder body of the present invention uses an anti-pinch telescopic ladder with application number 201820421159.4.

[0049] like Figure 9 As shown, when the telescopic ladder body is not extended, the two ends of the upper telescopic rod 10 in each frame 3 are movably connected to the two side plates 4 through the second positioning hole 20. In the other frames except the bottom frame, the two ends of the lower telescopic rod 10 are movably connected to the two adjacent side plates 4 through the first positioning hole 19 of the lower adjacent frame. The two ends of the lower telescopic rod 10 in the bottom frame are movably connected to the two side plates 4 through the third positioning hole 21, so that the three frames 3 of the protective cover are connected as one unit. This invention can be used as a transport trolley. The movable plates 5 of the three frames 3 cover the equipment and materials. The telescopic ladder body, support rod 29 and roller 30 form the trolley body. Maintenance personnel do not need to carry maintenance equipment and materials, which can reduce the burden on maintenance personnel and ensure the integrity of equipment and materials in case of emergencies.

[0050] like Figure 8 As shown, first open the clamping plate 25 of the hook 23 and use the bolt 26 to limit it. Then, disassemble the uppermost frame 3 and the middle frame 3 of the three frames 3, and flip the uppermost frame 3 to the left side of the telescopic ladder body. Then, adjust the movable plate 5 of each frame 3 as follows: Figure 8The state shown (i.e., before disassembly, the two telescopic rods 10 of the movable plate 5 of the uppermost frame 3 are connected to the second positioning hole 20 and the third positioning hole 21 respectively; before disassembly, the two telescopic rods 10 of the middle frame 3 are connected to the second positioning hole 20 and the first positioning hole 19 of the adjacent frame 3 below respectively; before disassembly, the telescopic rods 10 in the hinge shaft tube 13 at the hinge ends of the two blades 9 of the lowermost frame 3 are connected to a set of adjustment holes 22, so that the blades 9 connected to the fixed shaft 8 are close to the horizontal state, and the two ends of the telescopic rods 10 connected to the lower end of the lower blade 9 are connected to the second positioning hole 20 or not connected to any positioning hole, only in contact with the side plate 4), then the telescopic ladder is extended, and hooked onto the steel strand of the optical cable via the hook 23. The maintenance personnel climb onto the telescopic ladder body and rotate Loosen bolt 26, then fasten clamping plate 25, and finally use bolt 26 to limit the position. At this time, after flipping, the movable plate 5 of the frame 3 on the left side of the telescopic ladder body forms a support platform for placing maintenance equipment and materials. The movable plate 5 of the lower frame 3 of the two frames 3 on the right side of the telescopic ladder body forms a step for sitting. The movable plate 5 of the upper frame 3 of the two frames 3 on the right side of the telescopic ladder body forms a backrest to protect maintenance personnel and prevent them from falling. In addition, the cone 28 at the bottom of the telescopic ladder body penetrates into the soil, ensuring the stability of the telescopic ladder body even if the maintenance personnel move a lot. This invention is convenient for maintenance operations and has a protective function. Since the adjustment hole 22 can make the movable plate 5 on the lowermost frame 3 of the three frames 3 form a step for sitting, it is convenient for maintenance personnel to work and rest.

[0051] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various modifications can be made to the technical solutions of the present invention without departing from the spirit of the present invention or the scope of disclosure.

Claims

1. A telescopic ladder, comprising a telescopic ladder body, the telescopic ladder body comprising multiple sets of ladder tubes (1), wherein in two adjacent sets of ladder tubes (1), the upper ladder tube (1) retracts into the lower ladder tube (1), and a crossbar (2) is provided between each set of ladder tubes (1), characterized in that, The front and rear ends of the top horizontal bar (2) of the telescopic ladder body are both through the front and rear ladder tubes (1), and a protective cover is hinged between the two ends. The protective cover is composed of three frames (3). Each frame (3) includes two side plates (4) and a movable plate (5) movably connected between the two side plates (4). There is a fixed shaft (8) between the upper ends of the two side plates (4) and a movable plate (5) near the outer edge of the two side plates (4). The movable plate (5) includes a telescopic rod (10) and two blades (9) hinged together. The upper end of the upper blade (9) is rotatably connected to the fixed shaft (8). The telescopic rod (10) is hinged at the hinge point of the two blades (9) and at the lower end of the lower blade (9). The two ends of the telescopic rod (10) are movably connected to the two side plates (4). The side plates (4) on the same side of the three frames (3) are on the same vertical plane. The lowest frame (3) is provided with a roller (11) near the outer edge of the frame (3) and the lower end of the frame (3). The outer peripheral wall of the roller (11) is in rolling contact with the ladder tube (1). Each of the frame (3) has two side plates (4) that are symmetrical front and back. Both side plates (4) are fan-shaped plates. Both side plates (4) are rotatably connected to the two ends of the uppermost crossbar (2) through the connecting ring (6) at the center. Each of the two side plates (4) of the frame (3) is provided with corresponding positioning holes (7). The positioning holes (7) include a first positioning hole (19), a second positioning hole (20) and a third positioning hole (21). The first positioning hole (19) is located between the fixed shaft (8) and the outer edge of the side plate (4). The second positioning hole (20) is close to the middle of the outer edge of the side plate (4). The third positioning hole (21) is close to the middle of the lower edge of the side plate (4). In each of the two telescopic rods (10) within each frame (3), the two ends of the upper telescopic rod (10) are movably connected to the two side plates (4) via the second positioning hole (20), and the two ends of the lower telescopic rod (10) are movably connected to the two side plates (4) via the third positioning hole (21); or in each of the two telescopic rods (10) within each frame (3), the two ends of the upper telescopic rod (10) are movably connected to the two side plates (4) via the second positioning hole (20), and in the two telescopic rods (10) within the remaining frames except the bottom frame, the two ends of the lower telescopic rod (10) are movably connected to the two adjacent side plates (4) below via the first positioning hole (19) of the adjacent frame below, and the two ends of the lower telescopic rod (10) in the bottom frame are movably connected to the two side plates (4) below via the third positioning hole (21).

2. The telescopic ladder according to claim 1, characterized in that, The blade (9) is a rectangular plate. There are grooves (12) in the middle of the two long sides of the blade (9) that are recessed into the blade (9) and open outward. There are hinge tubes (13) on the blades (9) on the front and back sides of the grooves (12). A telescopic rod (10) is installed in the hinge tube (13) at the hinge joint of the two blades (9) and in the hinge tube (13) at the lower end of the lower blade (9) of the two blades (9). The hinge tube (13) at the upper end of the upper blade (9) of the two blades (9) is sleeved on the fixed shaft (8).

3. A telescopic ladder according to claim 1, characterized in that, The two side plates (4) of the lowest frame (3) of the three frames (3) are provided with multiple sets of adjustment holes (22) corresponding to each other. Each of the multiple sets of adjustment holes (22) is arranged on a circle with the fixed shaft (8) of the side plate (4) as the center and the center distance between the second positioning hole (20) of the side plate (4) and the fixed shaft (8) as the radius. The two ends of the telescopic rod (10) located at the top of the lowest frame (3) are movably connected to the two side plates (4) through any set of adjustment holes (22). When the two ends of the telescopic rod (10) located at the top of the lowest frame (3) are movably connected to the two side plates (4) through any set of adjustment holes (22), the two ends of the telescopic rod (10) located at the bottom of the lowest frame (3) are in contact with the side plate (4).

4. A telescopic ladder according to claim 3, characterized in that, The two ends of the telescopic rod (10) located at the top in the bottommost frame (3) are movably connected to the two side plates (4) through one of the adjustment holes (22). When the center distance between this set of adjustment holes (22) and the second positioning hole (20) on the side plate (4) is equal to the center distance between the two telescopic rods (10) on the movable plate (5), the two ends of the telescopic rod (10) located at the bottom in the bottommost frame (3) are movably connected to the two side plates (4) through the second positioning hole (20).

5. A telescopic ladder according to claim 1, characterized in that, The telescopic rod (10) includes a sleeve (14), two sliding rods (15) and a compression spring (18). The sleeve (14) is installed inside the hinge tube (13) and slides in contact with the hinge tube (13). The middle part of the peripheral wall of the sleeve (14) is provided with a through hole (16) corresponding to the through groove (12) on the blade (9). The front and rear parts of the sleeve (14) are provided with sliding rods (15) that slide in contact with the inner peripheral wall of the sleeve (14). The outer peripheral walls of the opposite ends of the two sliding rods (15) are provided with levers (17) that extend out of the through hole (16). The other ends of the two sliding rods (15) extend out of the sleeve (14). The corresponding through hole (16) between the opposite ends of the two sliding rods (15) is provided with a compression spring (18) located inside the sleeve (14).

6. A telescopic ladder according to claim 1, characterized in that, The upper ends of the two ladder tubes (1) at the top of the telescopic ladder body are connected to hooks (23) with their free ends away from the protective cover. The hooks (23) are n-shaped rods formed by connecting two straight rods and an arc rod in sequence. The two straight rods of the hooks (23) are provided with corresponding through holes (24). A clamping plate (25) is hinged in the through hole (24) of one of the straight rods. The clamping plate (25) is a fan-shaped plate. The center of the clamping plate (25) is hinged to the upper end of the through hole (24). The free end of the hook (23) is provided with a threaded hole that passes through the free end of the hook (23) and connects to the through hole (24). A bolt (26) is connected in the threaded hole. The bolt (26) passes through the threaded hole and presses against the outer peripheral wall of the clamping plate (25).

7. A telescopic ladder according to claim 6, characterized in that, The outer peripheral wall of the clamping plate (25) is provided with serrations (27) that are inclined toward the free end of the hook (23). The end face where the upper end of the outer peripheral wall of the clamping plate (25) is connected to the center of the circle is the working surface of the clamping plate (25). The working surface of the clamping plate (25) is provided with a downward recessed semi-circular notch with an upward opening.

8. A telescopic ladder according to claim 1, characterized in that, The lower ends of the two ladder tubes (1) at the bottom of the telescopic ladder body are connected to a cone (28) with the tip pointing downwards. The two ladder tubes (1) at the bottom of the telescopic ladder body are each connected to a support rod (29) on the same side as the free end of the hook (23). The right end of the support rod (29) is connected to the ladder tube (1), and the left end is rotatably connected to a roller (30).

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