Leveling rod perpendicularity automatic correction device

Abstract

The invention discloses an automatic leveling rod perpendicularity correcting device, which relates to the field of measuring equipment and comprises a correcting frame, a bracket, a correcting ball and the like. The correction frame is provided with a correction cavity for mounting the leveling rod and a slidable protective door, and automatic vertical correction of the leveling rod is realized through the correction ball and the correction rod. The device is simple in structure and convenient to use, and the measuring precision and efficiency of the leveling rod are effectively improved.

Description

Technical Field

[0001] This application relates to the technical field of leveling staff calibration, and particularly to an automatic leveling staff verticality correction device. Background Art

[0002] In leveling measurement, the leveling staff is a key measurement tool that needs to be kept vertical during the measurement process. Currently, it is mainly held by hand by workers, and whether it is upright is determined by observing the horizontal bubble on the leveling staff. However, this method is inconvenient to operate, and it often requires multiple adjustments to make the leveling staff upright. During the measurement process, its upright state also needs to be maintained, which affects the measurement efficiency and accuracy. Summary of the Invention

[0003] In order to improve the problem that it is rather troublesome to manually correct the verticality of the leveling staff, this application provides an automatic leveling staff verticality correction device.

[0004] This application provides an automatic leveling staff verticality correction device, adopting the following technical solutions: An automatic leveling staff verticality correction device includes A correction frame, in which the leveling staff is installed; A bracket for supporting the correction frame; A correction ball, on which a correction rod is fixedly connected. One end of the correction rod is fixedly connected to the leveling staff, and the axis of the correction rod passes through the center of the ball of the correction ball and the center of gravity of the leveling staff; Among them, the correction frame includes a backboard, a top board fixed to the upper end of the backboard, and two parallel side boards. The top board and the two side boards are fixed on the same side of the backboard and enclose a correction cavity, and the leveling staff is located in the correction cavity; on the side of the top board away from the correction cavity, there is a first ball groove for the correction ball to move, and a correction hole communicating with the correction cavity is opened at the bottom of the first ball groove. The correction rod passes through the correction hole and moves in the correction hole along with the correction ball; The correction frame is also slidably connected with two protection doors for covering the correction cavity, and the two protection doors are located on the side of the side board away from the backboard; the correction frame is provided with a fixing component for locking the correction ball; the fixing component is linked with the protection door; when the two protection doors are opened to measure the reading of the leveling staff, the fixing component is in a fixed state of fixing the correction ball; when the two protection doors are closed, the fixing component is in an unlocking state of releasing the fixation of the corrector.

[0005] By adopting the above technical solutions, the cooperation of the correction frame, the bracket, the correction ball and the correction rod can automatically keep the leveling staff in a vertical state, without the need for manual multiple adjustments, simplifies the operation process, and improves the measurement accuracy and efficiency.

[0006] Optionally, the correction frame is provided with a linkage component for synchronously moving the two protective doors in relative or opposite directions.

[0007] By adopting the above technical solution and setting the linkage component, the two protective doors can be opened and closed at the same time, which enhances the convenience of operation. The user only needs to operate one protective door, and the other can move synchronously, which improves work efficiency.

[0008] Optionally, the linkage assembly includes a gear and a rack, the rack is fixed on the protective door, a horizontally extending slide groove is provided on the side of the top plate away from the back plate, the gear is rotatably connected to the middle part of the slide groove, the racks on the two protective doors are slidably connected in the slide groove and are always engaged with the gear; the top plate is located on two opposite groove walls above and below the slide groove and a limiting groove is provided on the side of the rack away from the tooth surface, and a limiting block slidably connected in the limiting groove is provided.

[0009] By adopting the above technical solution, the structure of the linkage assembly is specifically described, including the coordination of the gear and the rack, and the setting of the limit groove and the limit block, which ensures the stability and accuracy of the protective door during movement and prevents the occurrence of offset or jamming.

[0010] Optionally, the fixing assembly includes a fixed pressure plate, a guide rod is vertically fixed to the side of the top plate facing away from the correction cavity, the fixed pressure plate is slidably connected to the guide rod, and moves along the guide rod toward or away from the guide rod. The fixing assembly also includes an elastic member arranged on the guide rod, which provides the fixed pressure plate with a direction toward the top plate and presses the correction ball to be fixed in the first ball groove.

[0011] By adopting the above technical solution and the design of the fixing assembly, the correction ball can be reliably fixed through the cooperation of the fixing pressure plate and the elastic member. When the protective door is opened, the fixing pressure plate automatically presses the correction ball to prevent it from moving during the measurement process, thus ensuring the accuracy of the measurement.

[0012] Optionally, the fixing assembly also includes an unlocking block fixedly connected to the protective door, and the unlocking block is provided with a first extrusion slope on the side facing the fixed pressure plate for squeezing and sliding the fixed pressure plate upward; when the protective door is fully closed, the first extrusion slope slides open the fixed pressure plate and separates it from the correction ball.

[0013] By adopting the above technical solution and the unlocking block design, the fixed pressure plate can be automatically unlocked when the protective door is closed, which simplifies the operation process and improves the use efficiency.

[0014] Optionally, the correction frame further includes a reinforcement component linked to the protective door and used for reinforcing the bottom of the leveling staff; when the two protective doors are opened to measure the reading of the leveling staff, the reinforcement component supports the leveling staff; when the two protective doors are closed, the reinforcement component releases the support for the leveling staff.

[0015] By adopting the above technical solution, the reinforcement component can support the bottom of the leveling staff during measurement, improving the stability of the leveling staff and preventing shaking during the measurement process.

[0016] Optionally, the reinforcement component includes a needle-piercing frame arranged in the correction frame and sliding up and down along the correction cavity. A number of needles are fixed on the needle-piercing frame, and needle-piercing blocks for the needles to pierce are arranged on the peripheral side of the bottom of the leveling staff; a push block is fixed at the bottom of the protective door, and a second pressing inclined surface for squeezing and sliding the needle-piercing frame upward is arranged on the side of the push block facing the needle-piercing frame.

[0017] By adopting the above technical solution, the design of the needle-piercing frame further improves the stability of the leveling staff during measurement.

[0018] Optionally, a second ball groove for increasing the contact area with the correction ball is provided on the side of the fixed pressing plate facing the top plate.

[0019] By adopting the above technical solution, the design of the second ball groove increases the contact area between the fixed pressing plate and the correction ball, improving the fixing effect and stability.

[0020] Optionally, a rubber pad for increasing the friction force on the surface of the correction ball is installed in the second ball groove.

[0021] By adopting the above technical solution, the rubber pad increases the friction force between the fixed pressing plate and the correction ball, further improving the fixing effect of the correction ball.

[0022] In summary, the present application includes at least one of the following beneficial effects: 1. Due to the structural design of the correction ball and the correction rod in the present invention, the leveling staff can always maintain a vertical state under the action of gravity and the correction ball, thus realizing the automatic correction of the verticality of the leveling staff and improving the measurement accuracy.

[0023] 2. In the present invention, by setting a fixing component linked to the protective door, the correction ball is fixed during measurement to prevent it from moving during the measurement process, further ensuring the accuracy of measurement. When measurement is not required, the fixing of the correction ball can be released to facilitate other operations.

[0024] 3. The setting of the reinforcement component can provide stable support for the leveling staff during measurement, preventing it from shifting due to external forces, thus ensuring the accuracy of measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the overall structural schematic diagram of this embodiment; Figure 2 is the sectional schematic diagram of this embodiment; Figure 3 is the structural schematic diagram of the connection between the correction ball and the measuring ruler in this embodiment; Figure 4 is the partial sectional view of this embodiment; Figure 5 is the structural schematic diagram of the protective door in this embodiment; Figure 6 is the partial schematic diagram showing the fixing component in this embodiment; Figure 7 is the partial schematic diagram showing the reinforcement component in this embodiment; Figure 8 is the schematic diagram of the state when the protective door is closed in this embodiment; Figure 9 is the schematic diagram of the state when the protective door is opened in this embodiment.

[0026] Explanation of reference numerals: 1. Correction frame; 11. Back plate; 12. Top plate; 121. First ball groove; 1211. Drag reduction ball; 122. Correction hole; 123. Slide groove; 124. Limit groove; 13. Side plate; 131. Anti - detachment groove; 14. Correction cavity; 15. Fixed pressing plate; 151. Second ball groove; 1511. Rubber pad; 16. Guide rod; 17. Elastic member; 18. Stopper; 2. Bracket; 21. Bottom frame; 22. Support feet; 3. Correction ball; 31. Correction rod; 4. Protective door; 41. Unlock block; 411. First extrusion inclined surface; 42. Push block; 421. Second extrusion inclined surface; 5. Linkage component; 51. Gear; 52. Rack; 521. Limit block; 6. Needle - punching frame; 61. Needle head; 62. Anti - detachment block; 63. Needle - punching block; 7. Level ruler. Detailed implementation manners

[0027] The following further elaborates on this application in conjunction with the accompanying drawings.

[0028] The embodiment of this application discloses an automatic correction device for the verticality of a level ruler.

[0029] Refer to Figure 1 、 2, The automatic verticality correction device for a leveling staff includes a correction frame 1 and a support 2. The correction frame 1 includes a back plate 11, a top plate 12, and two parallel side plates 13. The top plate 12 and the two side plates 13 are both fixed on the same side of the back plate 11. The two side plates 13 are vertically arranged, and the top plate 12 is horizontally connected to the upper ends of the two side plates 13 and is perpendicular to the two side plates 13. The top plate 12 and the two side plates 13 enclose a correction cavity 14 on the back plate 11. The leveling staff 7 is installed in the correction cavity 14, and there is a certain distance between the leveling staff 7 and the inner wall of the correction cavity 14, so that during the automatic correction of the leveling staff 7, it will not contact the inner wall of the correction cavity 14.

[0030] The support 2 is used to support and fix the correction frame 1. Specifically, referring to Figure 1 , 2 , the support 2 includes a bottom frame 21 and two support feet 22 vertically welded to the bottom frame 21. The two support feet 22 are respectively fixedly connected to the two side plates 13, so that the correction frame 1 can be supported on the ground through the support 2. The bottom frame 21 is a rectangular frame structure formed by enclosing multiple support bottom rods, which can effectively reduce the contact area with the ground and is not prone to tilting when supporting the correction frame 1.

[0031] Referring to Figure 3 , 4 , the device further includes a correction ball 3. A correction rod 31 is fixed on the outer peripheral side of the correction ball 3. The other end of the correction rod 31 is fixedly connected to one end of the leveling staff 7, and the axis of the correction rod 31 passes through the center of the ball and the center of gravity of the leveling staff 7. A first ball groove 121 adapted to the correction ball 3 is opened on the top plate 12. A correction hole 122 communicating with the correction cavity 14 is opened at the bottom of the first ball groove 121 on the top plate 12. The aperture of the correction hole 122 is larger than the rod diameter of the correction rod 31. A part of the correction ball 3 is located in the first ball groove 121, and the correction rod 31 passes through the correction hole 122 and can move and correct in the correction hole 122.

[0032] When the support 2 and the correction frame 1 are placed at the position to be measured, the correction ball 3 will automatically adjust its position under the action of its own gravity and the correction rod 31, driving the leveling staff 7 to return to the vertical state, thus achieving the purpose of automatic correction. Since the leveling staff 7 is suspended in the correction frame 1, a rangefinder, such as a laser rangefinder, an infrared rangefinder, an ultrasonic rangefinder, etc., is installed at the bottom of the leveling staff 7 to measure the suspended height. Of course, the suspended height can also be measured by a manual tool such as a tape measure.

[0033] Referring to Figure 1The front end of the correction frame 1 is slidably connected to two protective doors 4, which are located on the side of the side plate 13 away from the back plate 11. When the two protective doors 4 are closed, the correction cavity 14 can be shielded inside, so that the level ruler 7 is not easily disturbed by the environment during the automatic leveling process. The protective door 4 is made of transparent glass or other materials, so that the observer can observe whether the level ruler 7 is leveled from the outside.

[0034] Reference Figure 1 A linkage assembly 5 is provided on the correction frame 1, and the linkage assembly 5 is used to allow the two protective doors 4 to move synchronously in relative or opposite directions.

[0035] Specifically, refer to Figure 4 , 5 The linkage assembly 5 includes a gear 51 and two racks 52. The two racks 52 are fixedly connected to the two protective doors 4 respectively. The tooth surfaces of the racks 52 of the two protective doors 4 are arranged opposite to each other and are staggered and parallel to each other. A horizontally extending slide 123 is provided on the side of the top plate 12 away from the back plate 11. The gear 51 is rotatably connected to the middle of the slide 123 through a rotating shaft. The racks 52 on the two protective doors 4 are slidably connected in the slide 123 and are always meshed with the gear 51.

[0036] When it is necessary to open or close the protection door 4 , only one protection door 4 needs to be driven to move, and the other protection door 4 will move synchronously under the action of the gear 51 and the rack 52 .

[0037] In order to prevent the rack 52 from being separated from the slide slot 123, a limit slot 124 is provided on the upper and lower opposite slot walls of the top plate 12 located at the slide slot 123, and a limit block 521 is provided on the side of the rack 52 away from the tooth surface, and the limit blocks 521 of the two racks 52 are respectively slidably connected in the two limit slots 124. When the limit block 521 abuts against the end of the limit slot 124 away from the gear 51, the protective door 4 is in a fully open state; when the limit block 521 abuts against the end of the limit slot 124 close to the gear 51, the protective door 4 is in a fully closed state.

[0038] Reference Figure 6 The correction frame 1 is provided with a fixing assembly for locking the correction ball 3, and the fixing assembly is linked with the protection door 4. When the two protection doors 4 are opened to measure the level rod 7 reading, the fixing assembly is in a fixed state of fixing the correction ball 3; when the two protection doors 4 are closed, the fixing assembly is in an unlocked state of releasing the fixation of the corrector.

[0039] Specifically, refer to Figure 4 , 6The fixing assembly includes a fixed pressure plate 15, and a guide rod 16 extending upward is vertically fixed to the side of the top plate 12 away from the correction cavity 14. The fixed pressure plate 15 is slidably connected to the guide rod 16, and moves along the guide rod 16 in a direction close to or away from the guide rod 16. During the movement, the fixed pressure plate 15 and the top plate 12 remain parallel. The fixing assembly also includes an elastic member 17, which is arranged on the guide rod 16 and provides an elastic force for the fixed pressure plate 15 to move toward the top plate 12. Under the action of its own gravity and the elastic force of the elastic member 17, the fixed pressure plate 15 presses and fixes the correction ball 3 in the first ball groove 121.

[0040] Specifically, the elastic member 17 includes a spring, a stopper 18 is fixed to one end of the guide rod 16 away from the top plate 12, the spring is sleeved on the guide rod 16, one end of the spring abuts against the stopper 18, and the other end abuts against the fixed pressing plate 15. In other embodiments, the elastic member 17 can also be replaced by a sponge pad, a spring sheet or other elastic workpiece.

[0041] Reference Figure 5 , 6 The fixing assembly also includes an unlocking block 41 fixedly connected to the protective door 4. The unlocking block 41 is provided with a first extrusion slope 411 on the side facing the fixed pressure plate 15. The first extrusion slope 411 is used to squeeze and slide the fixed pressure plate 15 upward.

[0042] When the protective door 4 is opened and located at the measuring position, the first extrusion slope 411 of the unlocking block 41 points to the position of the gap between the fixed pressure plate 15 and the top plate 12, and does not generate an upward thrust on the fixed pressure plate 15; when the protective door 4 is in the process of closing, the first extrusion slope 411 of the unlocking block 41 will contact the fixed pressure plate 15, and slide the fixed pressure plate 15 upward by squeezing the fixed pressure plate 15, so that the fixed pressure plate 15 releases the lock on the correction ball 3.

[0043] Reference Figure 7 The correction frame 1 also includes a reinforcement component that acts on the bottom of the level rod 7 to reinforce the level rod 7. The reinforcement component is linked with the protection door 4. When the two protection doors 4 are opened to measure the reading of the level rod 7, the reinforcement component supports the level rod 7; when the two protection doors 4 are closed, the reinforcement component releases the support for the level rod 7.

[0044] Reference Figure 7 , 8, the reinforcement component includes a needle punching frame 6. The needle punching frame 6 is located in the correction cavity 14 and can slide up and down along the correction cavity 14. A retaining groove 131 is provided at the bottom of the side plate 13 in the correction cavity 14. The retaining groove 131 extends vertically along the height direction of the correction cavity 14. A retaining block 62 is fixed to the outside of the needle punching frame 6. The retaining block 62 is slidably connected to the retaining groove 131 to prevent the needle punching frame 6 from detaching from the correction cavity 14. A number of needles 61 are fixed to the needle punching frame 6. A needle punching block 63 is fixed to the peripheral side of the bottom of the leveling staff 7. The needle punching block 63 is kept at a certain distance from the inner wall of the correction cavity 14 to allow the leveling staff 7 to move together with the needle punching block 63. The needle punching block 63 is on the movement path of the needles 61 and can be penetrated by the needles 61. The needle punching block 63 can be made of soft and easily punctured materials such as sponge, foam, silica gel, etc.

[0045] A push block 42 extending towards the back plate 11 is fixed to the bottom of the protective door 4. A second pressing slope 421 for squeezing and sliding the needle punching frame 6 upwards is provided on the side of the push block 42 facing the needle punching frame 6. When the protective door 4 is opened for measurement, the second pressing slope 421 of the push block 42 will push the needle punching frame 6 upwards, causing the needles 61 to penetrate into the needle punching block 63 of the leveling staff 7 to reinforce the bottom of the leveling staff 7, making it not easy for the leveling staff 7 to shake. When the protective door 4 is closed, the needle punching frame 6 will slide down under the action of gravity and separate from the needle punching block 63, automatically releasing the reinforcement of the leveling staff 7.

[0046] It should be noted here that the piercing action of the needles 61 is after the fixing step of the correction ball 3. That is, during the opening process of the protective door 4, the first pressing slope 411 will separate from the fixing pressing plate 15 first, causing the fixing pressing plate 15 to fix the correction ball 3. Then, during the continued opening process of the protective door 4, the second pressing slope 421 will penetrate into the needle punching block 63.

[0047] Of course, in other embodiments, the pressing of the first pressing slope 411 and the second pressing slope 421 can be carried out synchronously, or even the piercing of the needles 61 is carried out first, and then the correction ball 3 is fixed.

[0048] Refer to Figure 4 , in order to reduce the resistance during the automatic correction of the correction ball 3, a number of resistance reducing balls 1211 for supporting the correction ball 3 are evenly fixed on the inner wall of the first ball groove 121. That is, the resistance reducing balls 1211 lift the correction ball 3 in the first ball groove 121, and the resistance during the automatic correction of the correction ball 3 is reduced by reducing the contact area between the correction ball 3 and the first ball groove 121.

[0049] Refer to Figure 4 , in order to increase the fixing effect of the fixing pressing plate 15, a second ball groove 151 for increasing the contact area with the correction ball 3 is provided on the side of the fixing pressing plate 15 facing the top plate 12. A rubber pad 1511 for increasing the friction force with the surface of the correction ball 3 is installed in the second ball groove 151.

[0050] The implementation principle of the automatic verticality correction device for a leveling staff in the embodiments of this application is as follows: During actual use, the user only needs to install the leveling staff 7 in the correction frame 1 and close the protective door 4. As the protective door 4 is closed, the unlocking block 41 slides open the fixed pressing plate 15 through the first pressing slope 411, enabling the correction ball 3 to move freely in the correction hole 122; after the correction is completed, the protective door 4 is opened for measurement. At this time, the fixed pressing plate 15 automatically presses and fixes the correction ball 3 under the action of the elastic member 17, and the acupuncture frame 6 of the reinforcement assembly rises under the action of the push block 42, and the needle head 61 penetrates into the acupuncture block 63 of the leveling staff 7 to reinforce the bottom of the leveling staff 7; subsequently, the user can perform leveling measurement.

[0051] The above are all the preferred embodiments of this application. Without limiting the protection scope of this application accordingly, therefore: All equivalent changes made according to the structure, shape, and principle of this application shall be covered within the protection scope of this application.

Claims

1. An automatic verticality correction device for a leveling staff, characterized in that: including a correction frame (1) in which the leveling staff (7) is installed; a bracket (2) for supporting the correction frame (1); a correction ball (3) fixedly connected with a correction rod (31) thereon. One end of the correction rod (31) is fixedly connected with the leveling staff (7), and the axis of the correction rod (31) passes through the center of the correction ball (3) and the center of gravity of the leveling staff (7); Among them, the correction frame (1) includes a back plate (11), a top plate (12) fixed to the upper end of the back plate (11), and two parallel side plates (13). The top plate (12) and the two side plates (13) are fixed on the same side of the back plate (11) and enclose a correction cavity (14). The leveling staff (7) is located in the correction cavity (14); on the side of the top plate (12) away from the correction cavity (14), a first ball groove (121) for the correction ball (3) to move is provided, and a correction hole (122) communicating with the correction cavity (14) is provided at the bottom of the first ball groove (121). The correction rod (31) passes through the correction hole (122) and moves in the correction hole (122) along with the correction ball (3); Two protective doors (4) for shielding the correction cavity (14) are also slidably connected to the correction frame (1). The two protective doors (4) are located on the side of the side plate (13) away from the back plate (11); a fixing component for locking the correction ball (3) is provided on the correction frame (1); the fixing component is linked with the protective door (4); when the two protective doors (4) are opened to measure the reading of the leveling staff (7), the fixing component is in a fixed state of fixing the correction ball (3); when the two protective doors (4) are closed, the fixing component is in an unlocking state of releasing the fixation of the corrector.

2. The automatic verticality correction device for a leveling staff according to claim 1, wherein: A linkage component (5) for synchronously moving the two protective doors (4) towards opposite or relative directions is provided on the correction frame (1).

3. The automatic verticality correction device for a leveling staff according to claim 2, characterized in that: The linkage component (5) includes a gear (51) and a rack (52). The rack (52) is fixed on the protective door (4). A horizontally extending chute (123) is provided on the side of the top plate (12) away from the back plate (11). The gear (51) is rotatably connected to the middle of the chute (123). The racks (52) on the two protective doors (4) are both slidably connected in the chute (123) and always mesh with the gear (51); limiting grooves (124) are provided on the two opposite chute walls of the top plate (12) located above and below the chute (123), and limiting blocks (521) slidably connected in the limiting grooves (124) are provided on the side of the rack (52) away from the tooth surface.

4. An automatic verticality correction device for a leveling staff according to claim 3, characterized in that: The fixing component includes a fixing pressing plate (15). On the side of the top plate (12) facing away from the correction cavity (14), a guiding rod (16) is vertically fixed. The fixing pressing plate (15) is slidably connected to the guiding rod (16) and moves along the guiding rod (16) in a direction approaching or departing from the guiding rod (16). The fixing component further includes an elastic member (17) disposed on the guiding rod (16) to provide a direction towards the top plate (12) for the fixing pressing plate (15) and press and fix the correction ball (3) in the first ball groove (121).

5. An automatic verticality correction device for a leveling staff according to claim 4, characterized in that: The fixing component further includes an unlocking block (41) fixedly connected to the protective door (4). On the side of the unlocking block (41) facing the fixing pressing plate (15), there is a first pressing inclined surface (411) for squeezing and sliding the fixing pressing plate (15) upwards; when the protective door (4) is fully closed, the first pressing inclined surface (411) slides the fixing pressing plate (15) to separate from the correction ball (3).

6. The automatic verticality correction device for a leveling staff according to claim 1, characterized in that: The correction frame (1) further includes a reinforcement component linked with the protective door (4) for reinforcing the bottom of the leveling staff (7); when the two protective doors (4) are opened to measure the reading of the leveling staff (7), the reinforcement component supports the leveling staff (7); when the two protective doors (4) are closed, the reinforcement component releases the support for the leveling staff (7).

7. An automatic verticality correction device for a leveling staff according to claim 6, characterized in that: The reinforcement component includes a needle punching frame (6) disposed in the correction frame (1) and slidably moving up and down along the correction cavity (14). A plurality of needles (61) are fixed on the needle punching frame (6). Needle punching blocks (63) for the needles (61) to puncture are arranged on the circumferential side of the bottom of the leveling staff (7); a pushing block (42) is fixed to the bottom of the protective door (4). On the side of the pushing block (42) facing the needle punching frame (6), there is a second pressing inclined surface (421) for squeezing and sliding the needle punching frame (6) upwards.

8. An automatic verticality correction device for a leveling staff according to claim 4, characterized in that: On the side of the fixing pressing plate (15) facing the top plate (12), a second ball groove (151) is formed to increase the contact area with the correction ball (3).

9. The automatic verticality correction device for a leveling staff according to claim 8, characterized in that: A rubber pad (1511) for increasing the surface friction with the correction ball (3) is installed in the second ball groove (151).

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