Prestressed tendon tensioning and anchoring device

Abstract

The utility model discloses a prestressed tendon tensioning and anchoring device, which belongs to the technical field of building equipment and comprises a bottom plate, two first guide rods are arranged above the bottom plate in parallel, a moving seat is arranged on the first guide rods, a connecting mechanism is arranged on the moving seat, and a driving mechanism for driving the moving seat to move is arranged on the right side of the moving seat. A fixing plate is arranged on the right side of the concrete wall, an auxiliary clamping mechanism is arranged on the fixing plate, the finish-rolled twisted steel penetrates through the fixing plate and the auxiliary clamping mechanism and then is connected with the connecting mechanism, and a locking mechanism is arranged on the right side of the auxiliary clamping mechanism. The first driving piece, the worm, the worm gear, the first gear and the rack are matched to drive the moving seat to move rightwards, finish rolling twisted steel is tensioned, and operation is convenient; the auxiliary clamping mechanism and the locking mechanism are matched for anchoring, gradual loosening caused by vibration is avoided, and the requirements of modern constructional engineering for high-quality, high-efficiency and high-safety construction are met.

Description

Technical Field

[0001] The utility model relates to the technical field of construction equipment, in particular to a tensioning and anchoring device for prestressed tendons. Background Technique

[0002] In the field of construction engineering, especially in projects involving prestressed concrete structures, the precision rolled thread steel is widely used in constructing prestressed systems due to its unique advantages. The precision rolled thread steel is a straight bar of hot-rolled steel with continuous external threads, and at any cross-section, it can be connected or anchored with a connector or anchor with a matching internal thread shape. It has the advantages of simple connection and anchoring, strong adhesion, safe and reliable tensioning and anchoring, convenient construction, etc., and can save steel bars, reduce the area and weight of components.

[0003] The existing precision rolled thread steel tensioning and anchoring technology has exposed many problems in practical applications. The traditional tensioning method of precision rolled thread steel often uses a hydraulic jack to tension to the design stress. The jack is a precision instrument, and after long-term use, it is prone to problems such as oil leakage, seal ring aging, and pressure gauge failure. It needs to be regularly maintained and calibrated, and the maintenance cost is relatively high. Moreover, equipment failures may lead to construction interruptions; when the jack is used for tensioning operations in high-temperature and low-temperature environments, the performance of the equipment may be affected. For example, low temperature will increase the viscosity of the hydraulic oil, resulting in unstable tensioning pressure. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a tensioning and anchoring device for prestressed tendons, which solves the problem that the use of a jack for tensioning may affect the tensioning effect due to its own problems.

[0005] To solve the above technical problems, the utility model adopts the following technical solutions:

[0006] A tensioning and anchoring device for prestressed tendons of the utility model includes a bottom plate. Above the bottom plate, two first guide rods are arranged in parallel. A moving seat is arranged on the first guide rods. A connecting mechanism is arranged on the moving seat. A driving mechanism for driving the movement of the moving seat is arranged on the right side of the moving seat. A fixing plate is arranged on the right side of the concrete wall. An auxiliary clamping mechanism is arranged on the fixing plate. The precision rolled thread steel passes through the fixing plate and the auxiliary clamping mechanism and then is connected with the connecting mechanism. A locking mechanism is arranged on the right side of the auxiliary clamping mechanism.

[0007] Further, the driving mechanism includes a rotating shaft arranged in a protective box. A worm gear and a first gear are arranged on the rotating shaft. A worm is meshed and connected above the worm gear. A first driving part is arranged at the exposed end of the worm. A rack is meshed and connected to the bottom of the first gear. The left end of the rack is connected with the moving seat. A slide rail is arranged on the top surface of the bottom plate. A slide block matching the slide rail is arranged on the bottom surface of the rack.

[0008] Furthermore, the connecting mechanism includes two second guide rods arranged side by side in the front and rear. The second guide rods are arranged on the top surface of the moving seat. A moving frame is arranged between the two second guide rods. A connecting nut and a driving assembly for driving the connecting nut to rotate are arranged on the moving frame. Internal threads matching the external threads of the precision rolled ribbed steel bars are provided on the inner wall of the connecting nut.

[0009] Furthermore, the driving assembly includes a second driving member. The second driving member is arranged on the right side of the moving frame. A second gear connected to the output end of the second driving member is arranged on the left side of the moving frame. A third gear meshing with the second gear is arranged on the outside of the connecting nut.

[0010] Furthermore, the auxiliary clamping mechanism includes a fixing ring. The fixing ring is arranged on the right side of the fixing plate. A through hole for the precision rolled ribbed steel bars to pass through is arranged at the central position of the fixing ring. A plurality of clamping blocks capable of moving radially are arranged around the through hole.

[0011] Furthermore, each clamping block includes an integrally formed sliding portion and a clamping portion. A sliding groove matching the sliding portion is arranged on the fixing ring. The outer side surface of the clamping portion is set as an inclined surface.

[0012] Furthermore, the locking mechanism includes a locking sleeve. An inner hole is arranged inside the locking sleeve. The inner hole includes a connecting hole and a limiting hole. Internal threads matching the external threads of the precision rolled ribbed steel bars are arranged on the inner wall of the connecting hole. The limiting hole is arranged on the left side of the connecting hole. The limiting hole is set as a tapered hole; after a plurality of the clamping portions clamp the precision rolled ribbed steel bars, the outer side surface of the clamping portion contacts the inner wall of the limiting hole.

[0013] Furthermore, a loosening prevention assembly is arranged on the outside of the locking sleeve. The loosening prevention assembly includes a ratchet wheel arranged on the outside of the locking sleeve. Connecting frames are rotatably arranged on the outside of the locking sleeve and on the left and right sides of the ratchet wheel. A pawl matching the ratchet wheel is arranged between the two connecting frames. A limiting plate is arranged in front of the two connecting frames. A spring is arranged on the rear side of the limiting plate. The other end of the spring is connected to the pawl.

[0014] Furthermore, a limiting rod for limiting the connecting frame is also arranged on the right side of the fixing plate. A connecting pipe is arranged at a position close to the top between the two connecting frames. A through hole communicating with the connecting pipe is arranged on the connecting frame. The limiting rod penetrates through the through hole and the connecting pipe. The connecting frame moves left and right along the limiting rod.

[0015] Furthermore, the limiting rod is provided as a screw rod, the sizes of the through hole and the connecting pipe are both larger than the size of the limiting rod, and a nut for limiting the connecting frame is threadedly connected to the limiting rod.

[0016] Compared with the prior art, the beneficial technical effects of the present utility model are as follows:

[0017] The present utility model designs a new tensioning structure. Above the bottom plate, two first guide rods are arranged in parallel. A moving seat is arranged on the first guide rods. On the right side of the moving seat, a driving mechanism for driving the movement of the moving seat is provided. The driving mechanism includes a worm gear, a first gear, a worm, and a rack. A first driving member drives the worm to rotate. The rotation of the worm drives the worm gear to rotate. The rotation of the worm gear drives the rotating shaft to rotate. The rotation of the rotating shaft drives the first gear to rotate. The rotation of the first gear drives the rack to move to the right. The movement of the rack to the right drives the moving seat to move to the right, so as to tension the high-strength steel bar. The operation is convenient and is not easily affected by its own structure and environmental factors. The auxiliary clamping mechanism and the locking mechanism cooperate for anchoring, avoiding gradual loosening due to vibration, and meeting the requirements of modern construction projects for high-quality, high-efficiency, and high-safety construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The following further describes the present utility model with reference to the accompanying drawings.

[0019] Figure 1 It is the front view of the prestressed tendon tensioning and anchoring device of the present utility model in the unlocked state;

[0020] Figure 2 It is the front view of the prestressed tendon tensioning and anchoring device of the present utility model in the locked state;

[0021] Figure 3 It is the top view of the connecting mechanism, the moving seat, and the driving mechanism of the present utility model;

[0022] Figure 4 It is the three-dimensional structure schematic diagram of the driving mechanism of the present utility model;

[0023] Figure 5 It is the three-dimensional structure schematic diagram of the connecting mechanism of the present utility model;

[0024] Figure 6 It is the front view of the auxiliary clamping mechanism of the present utility model;

[0025] Figure 7 It is the side view of the auxiliary clamping mechanism of the present utility model;

[0026] Figure 8 It is the three-dimensional structure schematic diagram of the locking mechanism of the present utility model;

[0027] Figure 9It is a cross-sectional view of the locking mechanism of the present utility model;

[0028] Figure 10 It is a three-dimensional structural schematic diagram of another angle of the locking mechanism of the present utility model.

[0029] Explanation of reference numerals in the drawings: 1, bottom plate; 2, protective box; 3, worm; 4, rotating shaft; 5, worm wheel; 6, first driving member; 7, first gear; 8, rack; 9, slide rail; 10, slider; 11, first guide rod; 12, moving seat; 13, connecting mechanism; 13-1, second guide rod; 13-2, moving frame; 13-3, second driving member; 13-4, second gear; 13-5, connecting nut; 13-6, third gear; 14, fixing plate; 15, auxiliary clamping mechanism; 15-1, fixing ring; 15-1-1, through hole; 15-1-2, chute; 15-2, clamping block; 15-2-1, sliding part; 15-2-2, clamping part; 16, locking mechanism; 16-1, locking sleeve; 16-1-1, inner hole; 16-1-1-1, connecting hole; 16-1-1-2, limiting hole; 16-2, ratchet wheel; 16-3, connecting frame; 16-4, ratchet pawl; 16-5, connecting pipe; 16-6, limiting plate; 16-7, spring; 17, limiting rod; 18, precision rolled threaded steel bar; 19, concrete wall. Specific implementation manners

[0030] As Figure 1-10 shown, a prestressed tendon tensioning and anchoring device includes a bottom plate 1. Above the bottom plate 1, two first guide rods 11 are arranged in parallel. Both ends of the first guide rods 11 are connected above the bottom plate 1 through supports. A moving seat 12 is slidably connected to the first guide rods 11. A connecting mechanism 13 is installed on the moving seat 12. On the right side of the moving seat 12, a driving mechanism for driving the movement of the moving seat 12 is provided. On the right side of a concrete wall 19, a fixing plate 14 is provided. An auxiliary clamping mechanism 15 is connected to the fixing plate 14. A precision rolled threaded steel bar 18 passes through the fixing plate 14 and the auxiliary clamping mechanism 15 and is connected to the connecting mechanism 13. A locking mechanism 16 is provided on the right side of the auxiliary clamping mechanism 15; specifically, when in use, the bottom plate 1 is fixed on the ground or other support frames and remains stationary. The driving mechanism is used to drive the moving seat 12 to move to the right to tension the precision rolled threaded steel bar 18. After the tensioning is completed, the auxiliary clamping mechanism 15 and the locking mechanism 16 are used for anchoring.

[0031] As Figure 4As shown in the figure, the driving mechanism includes a rotating shaft 4 rotatably installed in the protective box 2 through a bearing. A worm wheel 5 and a first gear 7 are installed on the rotating shaft 4. Above the worm wheel 5, there is a meshed connection with a worm 3. The worm 3 is rotatably connected to the protective box 2 through a bearing. An exposed end of the worm 3 is installed with a first driving member 6. At the bottom of the first gear 7, there is a meshed connection with a rack 8. The left end of the rack 8 is connected to the moving seat 12. On the top surface of the bottom plate 1, a slide rail 9 is installed. On the bottom surface of the rack 8, there is a slider 10 that matches the slide rail 9. Specifically, the first driving member 6 can adopt a handwheel for manual tensioning, or the first driving member 6 can also adopt a motor to drive the worm 3 to rotate by the motor.

[0032] During use, the first driving member 6 drives the worm 3 to rotate. The rotation of the worm 3 drives the worm wheel 5 to rotate. The rotation of the worm wheel 5 drives the rotating shaft 4 to rotate. The rotation of the rotating shaft 4 drives the first gear 7 to rotate. The rotation of the first gear 7 drives the rack 8 to move to the right. The movement of the rack 8 to the right drives the moving seat 12 to move to the right to tension the precision rolled thread steel 18.

[0033] As Figure 5 shown in the figure, the connecting mechanism 13 includes two second guide rods 13-1 arranged side by side in the front and back. The two second guide rods 13-1 are connected to the top surface of the moving seat 12 through a support. Between the two second guide rods 13-1, a moving frame 13-2 is slidably installed. A connecting nut 13-5 and a driving component for driving the connecting nut 13-5 to rotate are installed on the moving frame 13-2. The connecting nut 13-5 is rotatably connected to the moving frame 13-2 through a bearing. The driving component includes a second driving member 13-3. The second driving member 13-3 is installed on the right side of the moving frame 13-2. On the left side of the moving frame 13-2, a second gear 13-4 connected to the output end of the second driving member 13-3 is installed. On the outer side of the connecting nut 13-5, a third gear 13-6 meshing with the second gear 13-4 is installed. Specifically, the second driving member 13-3 adopts a motor.

[0034] During use, the second driving member 13-3 drives the second gear 13-4 to rotate. The rotation of the second gear 13-4 drives the third gear 13-6 to rotate. The rotation of the third gear 13-6 drives the connecting nut 13-5 to rotate. Since internal threads matching the external threads of the precision rolled thread steel 18 are provided on the inner wall of the connecting nut 13-5, by rotating the connecting nut 13-5, the connecting nut 13-5 can be connected to the precision rolled thread steel 18. Since the precision rolled thread steel 18 does not move, when the connecting nut 13-5 rotates, it will also move in the left and right directions, thereby driving the moving frame 13-2 to move along the second guide rod 13-1.

[0035] As Figure 6-7As shown in the figure, the auxiliary clamping mechanism 15 includes a fixing ring 15-1 which is connected to the right side of the fixing plate 14. A through hole 15-1-1 for the high-strength threaded steel bar 18 to pass through is provided at the central position of the fixing ring 15-1. A hole is also provided at the corresponding position on the fixing plate 14. Four clamping blocks 15-2 that can move radially are installed around the through hole 15-1-1. The clamping block 15-2 includes an integrally formed sliding part 15-2-1 and a clamping part 15-2-2. An I-shaped sliding groove 15-1-2 matching the sliding part 15-2-1 is provided on the fixing ring 15-1. The outer side surface of the clamping part 15-2-2 is set as an inclined surface.

[0036] As Figure 8-10 shown in the figure, the locking mechanism 16 includes a locking sleeve 16-1. An inner hole 16-1-1 is provided inside the locking sleeve 16-1. The inner hole 16-1-1 includes a connecting hole 16-1-1-1 and a limiting hole 16-1-1-2. Internal threads matching the external threads of the high-strength threaded steel bar 18 are provided on the inner wall of the connecting hole 16-1-1-1. The limiting hole 16-1-1-2 is connected to the left side of the connecting hole 16-1-1-1. The limiting hole 16-1-1-2 is set as a tapered hole. After the four clamping parts 15-2-2 clamp the high-strength threaded steel bar 18, the outer side surface of the clamping part 15-2-2 contacts the inner wall of the limiting hole 16-1-1-2.

[0037] An anti-loosening component is installed on the outer side of the locking sleeve 16-1. The anti-loosening component includes a ratchet 16-2 fixedly installed on the outer side of the locking sleeve 16-1. Connecting frames 16-3 are rotatably installed on the outer side of the locking sleeve 16-1 and on the left and right sides of the ratchet 16-2 through bearings. A pawl 16-4 matching the ratchet 16-2 is connected between the two connecting frames 16-3 through a rotating shaft. The front sides of the two connecting frames 16-3 are detachably connected by bolts with a limiting plate 16-6. A hanging ring is connected to the rear side of the limiting plate 16-6. One end of a spring 16-7 is hooked on the hanging ring, and the other end of the spring 16-7 is connected to the pawl 16-4.

[0038] When the locking sleeve 16-1 rotates, it drives the ratchet wheel 16-2 on its outer side to rotate together. When the ratchet wheel 16-2 rotates, it pushes the pawl 16-4 upward. The pawl 16-4 compresses the spring 16-7. Due to the block of the limiting plate 16-6, the height of the pawl 16-4 being lifted can be limited. If the ratchet wheel 16-2 rotates in the reverse direction, the pawl 16-4 will block the ratchet wheel 16-2 to prevent the ratchet wheel 16-2 from reversing, thereby preventing the locking sleeve 16-1 from reversing and loosening. If it is necessary to loosen the locking sleeve 16-1, the limiting plate 16-6 needs to be removed, and the pawl 16-4 needs to be lifted completely so that it no longer restricts the movement of the ratchet wheel 16-2, and then the locking sleeve 16-1 can be unscrewed.

[0039] A limiting rod 17 for limiting the connecting frame 16-3 is also connected to the right side of the fixed plate 14. A connecting pipe 16-5 is connected between the two connecting frames 16-3 near the top position. A through hole communicating with the connecting pipe 16-5 is formed in the connecting frame 16-3. The limiting rod 17 passes through the through hole and the connecting pipe 16-5. During the process of screwing the locking sleeve 16-1 to the left, the connecting frame 16-3 moves leftward along the limiting rod 17.

[0040] In another embodiment, the limiting rod 17 is set as a screw rod. The sizes of the through hole and the connecting pipe 16-5 are both larger than the size of the limiting rod 17. A nut for limiting the connecting frame 16-3 is threadedly connected to the limiting rod 17. When the locking sleeve 16-1 is screwed to the anchoring position, the nut is installed on the limiting rod 17, and the nut is screwed tightly to the position close to the right connecting frame 16-3, so as to further lock the position of the connecting frame 16-3.

[0041] The using process of the present utility model is as follows:

[0042] Installation process: First, the fixed plate 14 is inserted into the free end of the precision rolled threaded steel bar 18 so that the fixed plate 14 contacts the concrete wall 19. Then, the locking sleeve 16-1 is screwed into the side close to the fixed plate 14 from the free end of the precision rolled threaded steel bar 18. After that, the free end of the precision rolled threaded steel bar 18 is close to the connecting nut 13-5. The second driving member 13-3 drives the second gear 13-4 to rotate. The second gear 13-4 rotates to drive the third gear 13-6 to rotate. The third gear 13-6 rotates to drive the connecting nut 13-5 to rotate, and the connecting nut 13-5 is connected to the precision rolled threaded steel bar 18.

[0043] Tensioning process: The first driving member 6 drives the worm 3 to rotate. The worm 3 rotates to drive the worm gear 5 to rotate. The worm gear 5 rotates to drive the rotating shaft 4 to rotate. The rotating shaft 4 rotates to drive the first gear 7 to rotate. The first gear 7 rotates to drive the rack 8 to move rightward. The rack 8 moves rightward to drive the moving seat 12 to move rightward to tension the precision rolled threaded steel bar 18.

[0044] Anchoring process: Tighten the locking sleeve 16-1 to the left. When the limiting hole 16-1-1-2 is close to the four clamping parts 15-2-2, the locking sleeve 16-1 moves to the left and pushes the four clamping blocks 15-2 to move toward the center until the fine-rolled threaded steel bar 18 is clamped.

[0045] After the anchoring is completed, the tensioning structure is dismantled, the connecting nut 13 - 5 is loosened, and the movable seat 12 is separated from the precision-rolled threaded steel bar 18 .

[0046] The embodiments described above are only descriptions of the preferred methods of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A prestressed tendon tensioning and anchoring device, characterized in that: It includes a bottom plate (1). Above the bottom plate (1), two first guide rods (11) are arranged in parallel. A moving seat (12) is arranged on the first guide rods (11). A connecting mechanism (13) is arranged on the moving seat (12). On the right side of the moving seat (12), there is a driving mechanism for driving the movement of the moving seat (12). On the right side of the concrete wall (19), there is a fixed plate (14). An auxiliary clamping mechanism (15) is arranged on the fixed plate (14). The fine rolled threaded steel bar (18) passes through the fixed plate (14) and the auxiliary clamping mechanism (15) and is connected to the connecting mechanism (13). On the right side of the auxiliary clamping mechanism (15), there is a locking mechanism (16).

2. The prestressed tendon tensioning and anchoring device according to claim 1, characterized in that: The driving mechanism includes a rotating shaft (4) arranged in a protective box (2). A worm gear (5) and a first gear (7) are arranged on the rotating shaft (4). Above the worm gear (5), there is a meshing connection with a worm (3). The exposed end of the worm (3) is provided with a first driving member (6). At the bottom of the first gear (7), there is a meshing connection with a rack (8). The left end of the rack (8) is connected to the moving seat (12). On the top surface of the bottom plate (1), there is a slide rail (9). On the bottom surface of the rack (8), there is a slider (10) matching the slide rail (9).

3. The prestressed tendon tensioning and anchoring device according to claim 1, characterized in that: The connecting mechanism (13) includes two second guide rods (13-1) arranged side by side in the front and back. The second guide rods (13-1) are arranged on the top surface of the moving seat (12). Between the two second guide rods (13-1), there is a moving frame (13-2). A connecting nut (13-5) and a driving component for driving the rotation of the connecting nut (13-5) are arranged on the moving frame (13-2). On the inner wall of the connecting nut (13-5), there is an internal thread matching the external thread of the fine rolled threaded steel bar (18).

4. The prestressed tendon tensioning and anchoring device according to claim 3, characterized in that: The driving component includes a second driving member (13-3). The second driving member (13-3) is arranged on the right side of the moving frame (13-2). On the left side of the moving frame (13-2), there is a second gear (13-4) connected to the output end of the second driving member (13-3). On the outside of the connecting nut (13-5), there is a third gear (13-6) meshing with the second gear (13-4).

5. The prestressed tendon tensioning and anchoring device according to claim 1, characterized in that: The auxiliary clamping mechanism (15) includes a fixed ring (15-1). The fixed ring (15-1) is arranged on the right side of the fixed plate (14). At the central position of the fixed ring (15-1), there is a through hole (15-1-1) through which the fine rolled threaded steel bar (18) can pass. Around the through hole (15-1-1), there are several clamping blocks (15-2) that can move radially.

6. The prestressed tendon tensioning and anchoring device according to claim 5, characterized in that: The clamping block (15-2) includes an integrally formed sliding part (15-2-1) and a clamping part (15-2-2). On the fixed ring (15-1), there is a sliding groove (15-1-2) matching the sliding part (15-2-1). The outer side surface of the clamping part (15-2-2) is set as an inclined surface.

7. The prestressed tendon tensioning and anchoring device according to claim 6, characterized in that: The locking mechanism (16) includes a locking sleeve (16-1). An inner hole (16-1-1) is provided inside the locking sleeve (16-1). The inner hole (16-1-1) includes a connecting hole (16-1-1-1) and a limiting hole (16-1-1-2). An internal thread matching the external thread of the precision rolled threaded steel bar (18) is provided on the inner wall of the connecting hole (16-1-1-1). The limiting hole (16-1-1-2) is arranged on the left side of the connecting hole (16-1-1-1), and the limiting hole (16-1-1-2) is arranged as a tapered hole. After a plurality of the clamping parts (15-2-2) clamp the precision rolled threaded steel bar (18), the outer side surface of the clamping part (15-2-2) contacts the inner wall of the limiting hole (16-1-1-2).

8. The prestressed tendon tensioning and anchoring device according to claim 7, characterized in that: A loosening prevention assembly is provided on the outer side of the locking sleeve (16-1). The loosening prevention assembly includes a ratchet wheel (16-2) provided on the outer side of the locking sleeve (16-1). Connecting frames (16-3) are rotatably arranged on the outer side of the locking sleeve (16-1) and on the left and right sides of the ratchet wheel (16-2). A ratchet pawl (16-4) matching the ratchet wheel (16-2) is arranged between the two connecting frames (16-3). A limiting plate (16-6) is arranged in front of the two connecting frames (16-3). A spring (16-7) is arranged on the rear side of the limiting plate (16-6), and the other end of the spring (16-7) is connected to the ratchet pawl (16-4).

9. The prestressed tendon tensioning and anchoring device according to claim 8, characterized in that: A limiting rod (17) for limiting the connecting frame (16-3) is further provided on the right side of the fixing plate (14). A connecting pipe (16-5) is arranged at a position close to the top between the two connecting frames (16-3). A through hole communicating with the connecting pipe (16-5) is provided on the connecting frame (16-3). The limiting rod (17) penetrates through the through hole and the connecting pipe (16-5), and the connecting frame (16-3) moves left and right along the limiting rod (17).

10. The prestressed tendon tensioning and anchoring device according to claim 9, characterized in that: The limiting rod (17) is provided as a screw rod. The sizes of the through hole and the connecting pipe (16-5) are both larger than the size of the limiting rod (17). A nut for limiting the connecting frame (16-3) is threadedly connected to the limiting rod (17).

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