Land surveying instrument

Abstract

The invention relates to the field of land exploration, and particularly discloses a land exploration instrument which comprises a measuring instrument and a support, the measuring instrument is detachably installed on the support, and the support comprises a fixed table, three supporting legs rotationally connected to the fixed table and a driving mechanism used for automatically unfolding the three supporting legs; according to the device, the lifting table moves upwards through the tensile force of the extension spring, so that the three supporting legs are automatically unfolded outwards at the same time, and in the rotating process of a hinge rod, due to the limiting effect of an adjusting screw rod, the hinge rod can stop rotating after abutting against the upper end of the adjusting screw rod; therefore, the three supporting legs can automatically stop after being unfolded by a certain angle, the surveying instrument can be erected conveniently, the three supporting legs are unfolded at the same time, it can be ensured that the surveying instrument is stable during erecting, the unfolding angle can be adjusted by rotating the adjusting screw, and the surveying instrument can be conveniently erected. The operator can balance the relationship between the unfolding time and the erection stability according to the condition of the working environment.

Description

Technical Field

[0001] The present invention relates to the field of land surveying, and specifically to a land surveying instrument. Background Art

[0002] Land boundary survey and demarcation, abbreviated as boundary survey and demarcation, is based on the needs of land expropriation, requisition, transfer, transfer, conversion of agricultural land, land use planning, and land development, consolidation, and reclamation. It is used to demarcate the land use scope on the spot, measure the boundary location, and map the current land use situation. The commonly used equipment mainly includes total stations, GPS positioning systems with limit slots, and measuring tools. These devices are mainly erected on the surveying position through tripods. Since the surveying position needs to be frequently changed during the boundary survey and demarcation process, it is necessary to frequently erect and move the surveying equipment. The tripod on the traditional surveying equipment needs to be manually unfolded by the operator one by one when it is unfolded. This not only makes the erection process relatively slow, but also because the three legs are not related to each other. If one of the legs is not unfolded in place, the entire tripod is in an inclined state, and the tripod needs to be adjusted during the surveying process, which affects the normal boundary survey and demarcation process. Summary of the Invention

[0003] The purpose of the present invention is to provide a land surveying instrument to overcome the above-mentioned defects in the prior art.

[0004] According to a land surveying instrument of the present invention, it includes a surveying instrument and a bracket. The surveying instrument is detachably installed on the bracket. The bracket includes a fixed platform, three support legs rotatably connected to the fixed platform, and a driving mechanism for automatically unfolding the three support legs. The support leg includes a rotating seat, a fixed seat, two connecting rods, and a secondary support leg. The rotating seat is rotatably connected to the outer periphery of the fixed platform. The two connecting rods are fixed between the rotating seat and the fixed seat. The secondary support leg passes through the fixed seat and is located between the two connecting rods. The secondary support leg is slidably connected to the fixed seat. A limiting mechanism is provided on the secondary support leg to fix the position of the secondary support leg between the two connecting rods. The driving mechanism includes a lifting platform and a damping cylinder. The upper end of the damping cylinder is fixed to the lower end surface of the fixed platform. A piston rod is slidably connected in the damping cylinder. The lower end of the piston rod extends out of the damping cylinder. The lifting platform is fixed to the lower end of the piston rod. A tension spring is fixed between the lower end of the damping cylinder and the upper end surface of the lifting platform. An articulated rod is rotatably connected between the outer periphery of the tension spring and the three rotating seats.

[0005] Further, a slider is fixed to the upper end of the secondary support leg. An inwardly concave arc groove is formed on the end surface of the slider close to the connecting rod. The connecting rod is inserted into the corresponding arc groove and is slidably connected to the corresponding arc groove. A support pad is fixed to the lower end of the secondary support leg. The support pad is located below the fixed seat.

[0006] Further, an installation groove recessed inward is formed on the outer end face of the auxiliary support leg. A circular groove recessed inward is formed on the bottom wall of the installation groove. Two through grooves which are symmetrically arranged and perpendicular to the connecting rod are formed on the side wall of the circular groove. A sliding rod is slidably connected in the circular groove. Arc-shaped elastic pieces are fixed to one ends of the two sliding rods close to each other. An elliptical rotating block is rotatably arranged between the two arc-shaped elastic pieces. A friction block is fixed to the end of the sliding rod away from the rotating block. A friction strip is fixed to the side face of the connecting rod close to the auxiliary support leg. When the arc-shaped elastic piece abuts against the minor axis of the rotating block, there is a gap between the friction block and the friction strip. When the arc-shaped elastic piece abuts against the major axis of the rotating block, the friction block and the friction strip are in close contact with each other.

[0007] Further, the arc-shaped elastic piece is arc-shaped. The upper and lower ends of the arc-shaped elastic piece are both in contact with the side wall of the circular groove. The curvature of the arc-shaped elastic piece is smaller than that of the side wall of the circular groove.

[0008] Further, a through hole is formed on the bottom wall of the circular groove. A rotating shaft is rotatably connected in the through hole. A cover body is fixed in the installation groove by bolts. The rotating shaft penetrates through the rotating block and the cover body. The rotating shaft is fixedly connected with the rotating block and rotatably connected with the cover body.

[0009] Further, a limiting end is fixedly arranged at the inner end of the rotating shaft. The limiting end abuts against the inner side face of the auxiliary support leg. A limiting groove is formed in the rotating shaft. A guiding hole is formed in the side wall of the limiting groove away from the limiting end. One end of the guiding hole close to the limiting end communicates with the limiting groove. The other end of the guiding hole away from the limiting end is open. The cross-section of the guiding hole along the sliding direction of the auxiliary support leg is smaller than the cross-section of the limiting groove in this direction. An extension rod is slidably connected in the guiding hole. A limiting part slidably connected with the limiting groove is fixedly arranged at one end of the extension rod close to the limiting end. A limiting spring is fixed between the limiting part and the bottom wall of the limiting groove. A knob located outside the cover body is fixed to the end of the extension rod away from the limiting end. Four limiting protrusions evenly distributed circumferentially with the rotating shaft as the center are fixedly arranged on the surface of the knob close to the cover body. Four limiting holes corresponding to the limiting protrusions are formed on the surface of the cover body close to the knob. The limiting protrusions can be inserted into the limiting holes.

[0010] Further, a damping cavity is formed in the damping cylinder. Hydraulic oil is stored in the damping cavity. A piston is slidably connected in the damping cavity. A vertically penetrating liquid through hole is formed in the piston. The upper end of the piston rod is fixed to the piston.

[0011] Further, a threaded block is fixed to the lower end face of the lifting platform. Three adjusting screws are threadedly connected to the threaded block. The three adjusting screws are respectively located below the three hinge rods. By rotating the threaded block, the distance between the upper end of the threaded block and the hinge rods can be adjusted.

[0012] The beneficial effects of the present invention are as follows: During the unfolding process of the present invention, due to the pulling force of the stretching spring, the lifting platform moves upward. By using the three hinge rods, the three rotating seats rotate outward simultaneously, thereby realizing the automatic outward unfolding of the three support feet at the same time. During the rotation of the hinge rods, due to the limiting effect of the adjusting screws, after the hinge rods abut against the upper ends of the adjusting screws, they can stop rotating, so that the three support feet can automatically stop after unfolding a certain angle, which is convenient for the erection of the theodolite. The three support feet are unfolded simultaneously, which can ensure the stability of the theodolite during erection, and the unfolding angle can be adjusted by rotating the adjusting screws. The operator can balance the relationship between the unfolding time and the erection stability according to the working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic structural diagram of the present invention; Figure 2 is a schematic structural diagram of the bracket in the present invention; Figure 3 is a schematic structural diagram of the support foot in the present invention; Figure 4 is an exploded view of the limiting mechanism in the present invention; Figure 5 is a sectional view of the limiting mechanism in the present invention; Figure 6 is the present invention Figure 5 magnified schematic diagram at A; Figure 7 is a schematic structural diagram of the driving mechanism in the present invention; Figure 8 is a sectional schematic view of the driving mechanism in the present invention.

[0014] In the figure: 10. Measuring instrument; 20. Fixed platform; 30. Rotating base; 31. Connecting rod; 32. Fixed seat; 33. Hinge rod; 34. Friction strip; 40. Auxiliary support leg; 401. Installation groove; 402. Circular groove; 403. Through groove; 41. Support pad; 42. Slide block; 43. Cover body; 431. Limit hole; 50. Lifting platform; 51. Damping cylinder; 52. Tensile spring; 53. Threaded block; 54. Adjusting screw; 55. Piston rod; 56. Damping cavity; 57. Piston; 58. Liquid through hole; 60. Rotating block; 61. Limit spring; 62. Knob; 621. Limit projection; 63. Extension rod; 64. Slide rod; 65. Friction block; 66. Rotating shaft; 661. Guide hole; 662. Limit groove; 67. Arc-shaped elastic piece; 68. Limit end; 69. Limit portion. Detailed implementation mode

[0015] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the attached Figure 1 The orientation or positional relationship is only for the convenience of simplifying the description of the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0016] In order to make the purpose and advantages of the present invention more clear, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific implementation modes of the present invention, and does not strictly limit the scope of protection specifically requested by the present invention. As used herein, the terms "up and down" and "left and right" do not limit their strict geometric definitions, but include tolerances for machining or human errors that are reasonable and inconsistent. The specific features of this land surveying instrument will be described in detail below: An embodiment of the present invention: Refer to Figures 1-8 , the present invention provides a land surveying instrument, including a measuring instrument 10 and a bracket. The measuring instrument 10 is detachably installed on the bracket. The bracket includes a fixed platform 20, three support feet rotatably connected to the fixed platform 20, and a driving mechanism for automatically unfolding the three support feet; The support feet include a rotating seat 30, a fixed seat 32, two connecting rods 31, and a secondary support foot 40. The secondary support foot 40 and the connecting rods 31 are both made of aluminum alloy. The rotating seat 30 is rotatably connected to the outer periphery of the fixed platform 20. The two connecting rods 31 are fixed between the rotating seat 30 and the fixed seat 32. The secondary support foot 40 passes through the fixed seat 32 and is located between the two connecting rods 31. The secondary support foot 40 is slidably connected to the fixed seat 32. A limiting mechanism is provided on the secondary support foot 40 to fix the position of the secondary support foot 40 between the two connecting rods 31. The part of the secondary support foot 40 where the limiting mechanism is provided is made of solid aluminum alloy material, and the rest of the secondary support foot 40 is hollow inside to reduce the weight of the secondary support foot 40; The driving mechanism includes a lifting platform 50 and a damping cylinder 51. The upper end of the damping cylinder 51 is fixed to the lower end surface of the fixed platform 20. A piston rod 55 is slidably connected inside the damping cylinder 51. The lower end of the piston rod 55 extends out of the damping cylinder 51. The lifting platform 50 is fixed to the lower end of the piston rod 55. A tension spring 52 is fixed between the lower end of the damping cylinder 51 and the upper end surface of the lifting platform 50. There are articulated rods 33 rotatably connected between the outer periphery of the tension spring 52 and the three rotating seats 30.

[0017] Refer to Figure 3 , a slider 42 is fixed to the upper end of the secondary support foot 40. The slider 42 is made of engineering plastic. An arc groove recessed inward is provided on the end face of the slider 42 close to the connecting rod 31. The connecting rod 31 is inserted into the corresponding arc groove and is slidably connected to the corresponding arc groove. A support pad 41 is fixed to the lower end of the secondary support foot 40. The support pad 41 is located below the fixed seat 32. The setting of the arc groove on the slider 42 ensures the sliding smoothness between the slider 42 and the connecting rod 31.

[0018] Refer to Figure 4 , an installation groove 401 recessed inward is provided on the outer end face of the secondary support foot 40. A circular groove 402 recessed inward is provided on the bottom wall of the installation groove 401. Two through grooves 403 that are symmetrically arranged and perpendicular to the connecting rod 31 are provided on the side wall of the circular groove 402. A sliding rod 64 is slidably connected inside the circular groove 402. Arc-shaped elastic pieces 67 are fixed to the ends of the two sliding rods 64 close to each other. An elliptical rotating block 60 is rotatably arranged between the two arc-shaped elastic pieces 67. A friction block 65 is fixed to the end of the sliding rod 64 away from the rotating block 60. A friction strip 34 is fixed to the side face of the connecting rod 31 close to the secondary support foot 40. When the arc-shaped elastic piece 67 abuts against the minor axis of the rotating block 60, there is a gap between the friction block 65 and the friction strip 34. When the arc-shaped elastic piece 67 abuts against the major axis of the rotating block 60, the friction block 65 and the friction strip 34 are in close contact. By rotating the rotating block 60, the two sliding rods 64 can be pushed away from the rotating block 60, so that the friction block 65 and the friction strip 34 are in close contact, thereby restricting the sliding of the secondary support foot 40 and ensuring that the secondary support foot 40 can maintain a supporting state after extending the length of the support foot.

[0019] Referring to Figure 4 , the arc-shaped elastic piece 67 is arc-shaped. Both the upper and lower ends of the arc-shaped elastic piece 67 are in contact with the side wall of the circular groove 402. The curvature of the arc-shaped elastic piece 67 is smaller than that of the side wall of the circular groove 402. When the rotating block 60 rotates until its short axis is parallel to the sliding rod 64, by using the elastic force of the arc-shaped elastic piece 67, the sliding rod 64 can be made to move in the direction close to the rotating block 60, so that the friction block 65 is disengaged from the friction strip 34, and then the auxiliary support foot 40 can slide freely between the connecting rod 31.

[0020] Referring to Figure 4 , a through hole is formed in the bottom wall of the circular groove 402. A rotating shaft 66 is rotatably connected in the through hole. A cover body 43 is fixed in the installation groove 401 by bolts. The rotating shaft 66 penetrates through the rotating block 60 and the cover body 43. The rotating shaft 66 is fixedly connected with the rotating block 60 and rotatably connected with the cover body 43. By rotating the rotating shaft 66, the rotating block 60 can be driven to rotate. The detachable connection between the cover body 43 and the installation groove 401 also facilitates the maintenance and replacement of the limiting mechanism.

[0021] Referring to Figures 4-6, a limiting end 68 is fixedly arranged at the inner end of the inner side of the rotating shaft 66. The limiting end 68 abuts against the inner side surface of the auxiliary support leg 40. A limiting groove 662 is formed in the rotating shaft 66. A guiding hole 661 is formed in the side wall of the limiting groove 662 far away from the limiting end 68. One end of the guiding hole 661 close to the limiting end 68 communicates with the limiting groove 662. The other end of the guiding hole 661 far away from the limiting end 68 is open. The cross-section of the guiding hole 661 along the sliding direction of the auxiliary support leg 40 is smaller than the cross-section of the limiting groove 662 in this direction. An extension rod 63 is slidably connected in the guiding hole 661. The cross-sections of the guiding hole 661 and the extension rod 63 are regular hexagons. A limiting part 69 slidably connected with the limiting groove 662 is fixedly arranged at one end of the extension rod 63 close to the limiting end 68. The cross-sections of the limiting part 69 and the limiting groove 662 are regular hexagons. A limiting spring 61 is fixed between the limiting part 69 and the bottom wall of the limiting groove 662. A knob 62 located outside the cover body 43 is fixed at the other end of the extension rod 63 far away from the limiting end 68. Four limiting protrusions 621 evenly distributed circumferentially with the rotating shaft 66 as the center are fixedly arranged on one surface of the knob 62 close to the cover body 43. Four limiting holes 431 corresponding to the limiting protrusions 621 are formed in one surface of the cover body 43 close to the knob 62. The limiting protrusions 621 can be embedded into the limiting holes 431. Under the pulling force of the limiting spring 61, the limiting protrusions 621 can be embedded into the limiting holes 431, so as to limit the rotation of the knob 62. When the knob 62 needs to be rotated, the knob 62 is pulled in the direction away from the auxiliary support leg 40, so that the limiting protrusions 621 are far away from the limiting holes 431, and then the knob 62 is rotated. Due to the sliding connection between the extension rod 63 and the guiding hole 661, the rotation of the extension rod 63 drives the rotation of the rotating shaft 66, and then the rotating block 60 rotates. The sliding connection between the limiting part 69 and the limiting groove 662 ensures that the extension rod 63 will not be separated from the rotating shaft 66.

[0022] Refer to Figure 7 , Figure 8 , a damping cavity 56 is formed in the damping cylinder 51. Hydraulic oil is stored in the damping cavity 56. A piston 57 is slidably connected in the damping cavity 56. A vertically penetrating liquid through hole 58 is formed in the piston 57. The upper end of the piston rod 55 is fixed on the piston 57. When the piston rod 55 moves up and down, the piston 57 moves accordingly. When the hydraulic oil in the damping cavity 56 passes through the liquid through hole 58, due to the viscous resistance of the hydraulic oil, the piston 57 moves slowly in the damping cavity 56, so as to prevent the three support legs from hitting the operators when they are unfolded too fast.

[0023] Refer to Figure 2 , Figure 8 , a threaded block 53 is fixed on the lower end surface of the lifting platform 50. Three adjusting screws 54 are threadedly connected to the threaded block 53. The three adjusting screws 54 are respectively located below the three hinge rods 33. By rotating the threaded block 53, the distance between the upper end of the threaded block 53 and the hinge rod 33 can be adjusted.

[0024] When the present invention is in use, when the present invention is moving, the three supporting legs are gathered together and tied with a cloth band. At this time, the lifting platform 50 is at the lowest position, the distance between the lifting platform 50 and the lower end of the damping cylinder 51 is the farthest, and the tension spring 52 is in a tensioned state.

[0025] When it moves to the survey position, the cloth tie is released. At this time, due to the tension of the tension spring 52, the lifting platform 50 moves upward, the piston rod 55 slides upward, and the piston 57 moves upward accordingly. Since the hydraulic oil in the damping chamber 56 encounters resistance when passing through the liquid hole 58, the piston 57 can only slide upward slowly, and the lifting platform 50 can only move upward slowly.

[0026] During the upward movement of the lifting platform 50, the three rotating seats 30 are pushed outward at the same time by the three hinged rods 33, so that the three supporting feet are simultaneously unfolded outward. Since the connection position between the upper end of the hinged rod 33 and the rotating seat 30 is close to the connection position between the rotating seat 30 and the fixed platform 20, when the lifting platform 50 moves upward a small distance and a slow speed, after being transmitted to the supporting feet, the unfolding angle and the unfolding speed of the supporting feet will be amplified to a certain extent, but the amplified unfolding speed will not be too fast, thereby avoiding hitting the operator.

[0027] When the three supporting legs are unfolded to a certain angle, the articulated rod 33 rotates to abut against the upper end of the adjusting screw 54, thereby limiting the rotation of the articulated rod 33, so that the supporting legs remain stationary after being unfolded. The angle of the articulated rod 33 after stopping can be adjusted by rotating the adjusting screw 54, thereby adjusting the unfolding angle of the three supporting legs. If the unfolding angle is larger, the unfolding process is longer, but the unfolded bracket is more stable, and vice versa. Therefore, the operator can choose an appropriate unfolding time according to the actual survey situation while ensuring the high stability of the bracket.

[0028] During the synchronous unfolding of the three supporting legs, the auxiliary supporting legs 40 slide downward along the corresponding connecting rods 31 under the action of their own gravity, thereby extending the length of the supporting legs.

[0029] When the supporting legs are fully unfolded, adjust the horizontal state of the fixed platform 20. At this time, pull the knob 62 in the direction away from the cover body 43, so that the limiting protrusion 621 is away from the limiting hole 431. After rotating ninety degrees, reinsert the limiting protrusion 621 into the limiting hole 431. At this time, since the knob 62 is rotated ninety degrees, the rotating shaft 66 rotates, thereby driving the rotating block 60 to rotate ninety degrees. The long axis of the rotating block 60 abuts against the arc-shaped elastic sheets 67 on both sides, thereby pushing the sliding rods 64 on both sides away from the rotating block 60, and the friction blocks 65 on both sides tightly abut against the friction strips 34, thereby limiting the sliding of the auxiliary support legs 40, thereby ensuring the supporting stability of the bracket.

[0030] After the survey is completed, turn the knob 62 ninety degrees to separate the two friction blocks 65 from the friction strips 34 on both sides. After the secondary support feet 40 are reset, then bundle the three support feet together with a cloth tie.

[0031] Those skilled in the art can clearly understand that various modifications to the above embodiments can be made without departing from the general spirit and concept of the present invention. All of them fall within the protection scope of the present invention. The protection scope of the present invention is subject to the claims attached to the present invention.

Claims

1. A land surveying instrument, comprising a measuring instrument (10) and a bracket, characterized in that: The measuring instrument (10) is detachably mounted on a bracket, wherein the bracket comprises a fixed platform (20), three supporting legs rotatably connected to the fixed platform (20), and a driving mechanism for automatically unfolding the three supporting legs; The supporting foot comprises a rotating seat (30), a fixed seat (32), two connecting rods (31) and a secondary supporting foot (40); the rotating seat (30) is rotatably connected to the outer periphery of the fixed platform (20); the two connecting rods (31) are fixed between the rotating seat (30) and the fixed seat (32); the secondary supporting foot (40) passes through the fixed seat (32) and is located between the two connecting rods (31); the secondary supporting foot (40) is slidably connected to the fixed seat (32); and a limiting mechanism is provided on the secondary supporting foot (40) for fixing the position of the secondary supporting foot (40) between the two connecting rods (31); The driving mechanism comprises a lifting platform (50) and a damping cylinder (51), the upper end of the damping cylinder (51) being fixed to the lower end surface of the fixed platform (20), a piston rod (55) being slidably connected inside the damping cylinder (51), the lower end of the piston rod (55) extending out of the damping cylinder (51), the lifting platform (50) being fixed to the lower end of the piston rod (55), a tension spring (52) being fixed between the lower end of the damping cylinder (51) and the upper end surface of the lifting platform (50), and a hinged rod (33) being rotationally connected between the outer periphery of the tension spring (52) and the three rotating seats (30).

2. A land surveying instrument according to claim 1, characterized in that: A slider (42) is fixed to the upper end of the auxiliary support leg (40); an inwardly recessed arc groove is formed on an end surface of the slider (42) close to the connecting rod (31); the connecting rod (31) is inserted into the corresponding arc groove and is slidably connected to the corresponding arc groove; a support pad (41) is fixed to the lower end of the auxiliary support leg (40); the support pad (41) is located on the lower side of the fixing seat (32).

3. A land surveying instrument according to claim 1, characterized in that: An inwardly recessed mounting groove (401) is provided on the outer end surface of the secondary support foot (40), an inwardly recessed circular groove (402) is provided on the bottom wall of the mounting groove (401), two symmetrically arranged through grooves (403) perpendicular to the connecting rod (31) are provided on the side wall of the circular groove (402), a sliding rod (64) is slidably connected in the circular groove (402), an arc-shaped elastic sheet (67) is fixed on the ends of the two sliding rods (64) close to each other, and a rotationally arranged between the two arc-shaped elastic sheets (67) The rotating block (60) is elliptical in shape, a friction block (65) is fixed to one end of the sliding rod (64) away from the rotating block (60), and a friction strip (34) is fixed to one side surface of the connecting rod (31) close to the auxiliary support leg (40); when the arc-shaped elastic sheet (67) abuts against the short axis of the rotating block (60), a gap exists between the friction block (65) and the friction strip (34); when the arc-shaped elastic sheet (67) abuts against the long axis of the rotating block (60), the friction block (65) and the friction strip (34) are tightly abutted.

4. A land surveying instrument according to claim 3, characterized in that: The arc-shaped elastic piece (67) is in an arc shape, and the upper and lower ends of the arc-shaped elastic piece (67) are in contact with the side wall of the circular groove (402), and the curvature of the arc-shaped elastic piece (67) is smaller than the curvature of the side wall of the circular groove (402).

5. A land surveying instrument according to claim 3, characterized in that: A through hole is provided on the bottom wall of the circular groove (402), a rotating shaft (66) is rotatably connected in the through hole, a cover body (43) is fixed in the mounting groove (401) by bolts, the rotating shaft (66) passes through the rotating block (60) and the cover body (43), the rotating shaft (66) is fixedly connected to the rotating block (60), and the rotating shaft (66) is rotatably connected to the cover body (43).

6. A land surveying instrument according to claim 5, characterized in that: A limiting end (68) is fixedly provided at one end of the inner side of the rotating shaft (66), and the limiting end (68) abuts against the inner side surface of the auxiliary support leg (40). A limiting groove (662) is provided in the rotating shaft (66), and a guide hole (661) is provided in a side wall of the limiting groove (662) away from the limiting end (68). An end of the guide hole (661) close to the limiting end (68) is communicated with the limiting groove (662), and an end of the guide hole (661) away from the limiting end (68) is open. The cross section of the guide hole (661) along the sliding direction parallel to the auxiliary support leg (40) is smaller than the cross section of the limiting groove (662) in the same direction. An extension rod (63) is slidably connected in the guide hole (661), and the extension rod (63) is slidably connected to the guide hole (661). A limiting portion (69) is fixedly provided at one end of the extension rod (63) close to the limiting end (68) and is slidably connected to the limiting groove (662); a limiting spring (61) is fixed between the limiting portion (69) and the bottom wall of the limiting groove (662); a knob (62) located outside the cover body (43) is fixedly provided at one end of the extension rod (63) away from the limiting end (68); four limiting protrusions (621) are fixedly provided on one side of the knob (62) close to the cover body (43) and are evenly distributed in the circumferential direction with the rotating shaft (66) as the center; and four limiting holes (431) corresponding to the limiting protrusions (621) are opened on one side of the cover body (43) close to the knob (62); and the limiting protrusions (621) can be embedded in the limiting holes (431).

7. A land surveying instrument according to claim 1, characterized in that: A damping chamber (56) is provided in the damping cylinder (51), hydraulic oil is stored in the damping chamber (56), a piston (57) is slidably connected in the damping chamber (56), a vertically penetrating liquid hole (58) is provided on the piston (57), and the upper end of the piston rod (55) is fixed on the piston (57).

8. A land surveying instrument according to claim 1, characterized in that: A threaded block (53) is fixed to the lower end surface of the lifting platform (50), and three adjusting screws (54) are threadedly connected to the threaded block (53). The three adjusting screws (54) are respectively located at the lower sides of the three hinged rods (33). The distance between the upper end of the threaded block (53) and the hinged rod (33) can be adjusted by rotating the threaded block (53).

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