Torsion-resistant floating bridge structure for concrete wetting trolley

Abstract

An anti-torsion floating bridge structure for a concrete wet spraying trolley belongs to the technical field of tunnel construction mechanical equipment and comprises a trolley body longitudinal beam assembly, a rotary table is fixedly connected to the trolley body longitudinal beam assembly, a rotating shaft is fixedly connected to the side wall of the rotary table, and a floating bridge body is rotatably connected to the suspended end of the rotating shaft. Four lead screws distributed in a cross shape are arranged on the floating bridge body, one ends of the four lead screws are detachably connected with the floating bridge body, the other ends of the four lead screws are adjustably connected with a vehicle body longitudinal beam through connecting assemblies, and a limiting assembly used for limiting deflection of the floating bridge body is arranged between the rotary table and the floating bridge body. Through the arrangement of the floating bridge body and the cross-shaped lead screw, the stress of the vehicle frame can be uniformly distributed, and the torsion resistance of the vehicle body is improved; meanwhile, the vibration amplitude of the vehicle body can be reduced through double guarantee of the limiting block and the sensor, and the effect of preventing the vehicle body from overturning is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tunnel construction machinery and equipment, and relates to a torsion-resistant floating bridge structure, in particular to a torsion-resistant floating bridge structure for a concrete wet spraying trolley. BACKGROUND

[0002] The concrete wet spraying trolley (also known as a wet spraying manipulator) is a large intelligent concrete wet spraying device integrating walking, pumping and spraying functions, and is mainly used for supporting operations in tunnel, culvert and slope engineering. It has the following advantages:

[0003] 1. Wireless remote control operation: the operator is away from the spraying surface, and the labor intensity is low;

[0004] 2. Wet spraying process: low rebound rate, material saving, low dust concentration and operation safety guarantee;

[0005] 3. High work efficiency, suitable for large-scale operation.

[0006] The concrete wet spraying trolley, as the core equipment for tunnel supporting construction, its chassis stability directly determines the spraying efficiency and construction safety. Especially under complex geological conditions, the trolley needs to frequently adjust the posture of the jib to cover large sections. In the adjustment process, the eccentric load and torsional load borne by the turntable are significantly improved, and when working in a large section of the tunnel, the telescopic arm telescopes and rotates 360°, and the jib-spraying head system will generate a large overturning moment. However, the traditional turntable is rigidly connected with the chassis, lacks a torsional load buffering mechanism, and is prone to trolley tilting or even overturning accidents, which seriously affects the spraying efficiency and operation safety.

[0007] Therefore, it is urgent to design a torsion-resistant floating bridge structure with simple structure and stable work, to improve the operation stability and safety of the concrete wet spraying trolley. SUMMARY

[0008] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a torsion-resistant floating bridge structure for a concrete wet spraying trolley, to solve the technical problem that the concrete wet spraying trolley in the prior art is prone to trolley tilting or even overturning accidents during work, which seriously affects the spraying efficiency and operation safety.

[0009] To achieve the above object and other related objects, the present application provides a kind of anti-torsion floating bridge structure for concrete wetting platform truck, including vehicle body longitudinal beam group, the vehicle body longitudinal beam group is fixedly connected with rotary table, rotary table side wall is fixedly connected with rotating shaft, the free end of the rotating shaft is rotatably connected with floating bridge body, four cross-distributed lead screws are provided on the floating bridge body, one end of the four lead screws is detachably connected with the floating bridge body, the other end is adjustably connected with the vehicle body longitudinal beam through connecting assembly, limiting assembly for limiting the deflection of floating bridge body is provided between the rotary table and the floating bridge body.

[0010] Preferably in any of the above solutions, the floating bridge body includes two first sealing plates arranged in parallel, the two first sealing plates are welded into a rectangular cavity by a second sealing plate, through holes are symmetrically formed in the two first sealing plates, and shaft sleeves are press-fitted in the through holes.

[0011] Preferably in any of the above solutions, mounting holes are formed around the floating bridge body, and the centers of the four mounting holes are on the same horizontal plane.

[0012] Preferably in any of the above solutions, a clamping ring groove is formed in the free end of the rotating shaft, and an axial limiting clamping ring is installed in the clamping ring groove, the rotating shaft is inserted into the shaft sleeve, and the axial displacement of the floating bridge body is limited by the limiting clamping ring.

[0013] Preferably in any of the above solutions, the connecting assembly includes two X-axis lead screw fixing plates and two Y-axis lead screw fixing plates, the two X-axis lead screw fixing plates are symmetrically fixed between the vehicle body longitudinal beam groups, and the two Y-axis lead screw fixing plates are fixed to the upper surfaces of the vehicle body longitudinal beam groups.

[0014] Preferably in any of the above solutions, the lead screws include two X-axis lead screws and two Y-axis lead screws, one end of each of the X-axis lead screws and the Y-axis lead screws is inserted into the mounting hole and fastened by a nut, and the other end of each of the X-axis lead screws and the Y-axis lead screws is fixed to the X-axis lead screw fixing plate and the two Y-axis lead screw fixing plates respectively and fastened by a hydraulic lock nut.

[0015] Preferably in any of the above solutions, the limiting assembly includes two limiting blocks and two limiting plates symmetrically arranged on both sides of the rotating shaft, the two limiting blocks are respectively arranged on the inner sides of the two limiting plates, the two limiting blocks are fixed to the side wall of the rotary table by a limiting block support, one end of each of the two limiting plates is connected to the side wall of the first sealing plate, and the other end of each of the two limiting plates is free.

[0016] Preferably in any of the above solutions, a sensor for detecting the deflection angle of the limiting plate is further installed on the limiting block support.

[0017] Preferably in any of the above solutions, the limiting block is detachably connected to the lower surface of the limiting block support, and the horizontal included angle between the outer wall of the limiting block and the inner wall of the limiting plate is 4°.

[0018] Preferably in any of the above solutions, the horizontal angle between the center of the sensor emitting end and the inner wall of the limiting plate is 3°.

[0019] As described above, the anti-torsion floating bridge structure of the concrete wet spraying trolley has the following beneficial effects:

[0020] 1. In the present application, the floating bridge body is connected between the turntable and the vehicle body longitudinal beam assembly, changing the rigid connection between the turntable and the chassis in the prior art. The floating bridge body can realize the function of torsional load buffering, thereby effectively avoiding vehicle body tilting, ensuring work efficiency and improving work safety.

[0021] 2. In the present application, the cross-shaped screw is arranged to uniformly decompose the torsional load into four-directional component forces and transmit them to the vehicle body longitudinal beam assembly, so as to uniformly distribute the stress of the vehicle frame and improve the torsional resistance of the vehicle body.

[0022] 3. In the present application, the limiting block and the sensor are arranged to constrain the deflection angle of the rotating shaft, thereby avoiding safety accidents caused by over-limit deflection. At the same time, the limiting block and the sensor can also double-protectively reduce the vibration amplitude of the vehicle body, thereby achieving the effect of preventing the vehicle body from overturning.

[0023] 4. In the present application, the entire device has strong working condition adaptability, and the hydraulic wrench can adjust the pre-tightening force and the torque according to soft rock strata and hard rock strata.

[0024] 5. In the present application, the limiting snap ring is designed to facilitate replacement of the rotating shaft, thereby improving the convenience of maintaining the floating bridge structure. DETAILED DESCRIPTION

[0025] Figure 1 The figure shows the structural schematic diagram of the present application.

[0026] Figure 2 The figure shows the connection structure schematic diagram of the turntable and the rotating shaft.

[0027] Figure 3 The figure shows the structural schematic diagram of the floating bridge body.

[0028] Figure 4 The figure shows the top view of the connection between the cross-shaped screw and the vehicle body longitudinal beam assembly.

[0029] Figure 5 The figure shows the front view of the connection between the cross-shaped screw and the vehicle body longitudinal beam assembly.

[0030] Figure 6 The figure shows the connection structure schematic diagram of the limiting assembly.

[0031] Element number explanation

[0032] 1-turret; 11-support body; 12-support cylinder; 13-slewing bearing; 14-slewing support; 2-floating bridge body; 21-first sealing plate; 22-second sealing plate; 23-bush; 24-mounting hole; 3-rotary shaft; 31-limiting snap ring; 4-screw rod; 41-X-axis screw rod; 42-Y-axis screw rod; 43-X-axis screw rod fixing plate; 44-Y-axis screw rod fixing plate; 45-hydraulic locking nut; 46-nut; 5-limiting assembly; 51-limiting block; 52-limiting block support; 53-sensor; 54-limiting plate; 55-rib plate; 6-car body longitudinal beam assembly; 61-upper wing plate; 62-web; 63-lower wing plate. DETAILED DESCRIPTION

[0033] The implementation of the present application is illustrated by specific embodiments below, and other advantages and effects of the present application can be easily understood by those skilled in the art from the content disclosed in the specification.

[0034] Please refer to Figures 1 to 6 It should be understood that the structures, proportions, sizes, etc. shown in the drawings attached to the specification are only used to illustrate the content disclosed in the specification for the understanding and reading of those skilled in the art, and are not used to limit the defined conditions under which the present application can be implemented, and therefore do not have technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that can be produced by the present application and the purposes that can be achieved, should still fall within the scope of the technical content disclosed by the present application. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" used in the specification are only for the purpose of clear understanding of the description, and are not used to limit the scope in which the present application can be implemented, and the change or adjustment of the relative relationship, without substantially changing the technical content, is also considered as the scope in which the present application can be implemented.

[0035] Please refer to Figures 1-6 The present application provides a torsion-resistant floating bridge structure for a concrete wet spraying trolley, which comprises a car body longitudinal beam assembly 6, a turret 1 fixedly connected to the car body longitudinal beam assembly 6, a rotary shaft 3 connected to the side wall of the turret 1, and a floating bridge body 2 rotatably connected to the free end of the rotary shaft 3. The flexible connection between the turret 1 and the car body longitudinal beam assembly 6 is achieved through the connection of the rotary shaft 3 and the floating bridge body 2, which changes the connection mode of the rigid connection between the turret 1 and the chassis in the prior art, forms a torsional load cushioning mechanism between the turret 1 and the car body longitudinal beam assembly 6, reduces the inclination of the car body, and ensures the spraying efficiency and operation safety.

[0036] At the same time, the four cross-distributed screw rods 4 arranged between the floating bridge body 2 and the car body longitudinal beam assembly 6 can uniformly decompose the torsional load into four-directional component forces and transmit them to the car body longitudinal beam assembly 6, so as to uniformly distribute the stress of the car frame and improve the torsional resistance of the car body.

[0037] Specifically,

[0038] The vehicle body longitudinal beam assembly 6 comprises two parallel webs 62, each of which is integrally connected with an upper flange 61 and a lower flange 63 at the upper and lower ends thereof, so as to form a H-shaped structure.

[0039] The rotary table 1 comprises a support body 11, a support cylinder 12, a rotary bearing 13 and a rotary support 14. The support body 11 is fixed to the upper surface of the upper flange 61, the support cylinder 12 is fixedly connected above the support body 11, the rotary bearing 13 is rotatable by 360° and is connected above the support cylinder 12, and the rotary support 14 is connected above the rotary bearing 13.

[0040] The floating bridge body 2 comprises two parallel first sealing plates 21, which are welded into a rectangular cavity through a second sealing plate 22, and symmetrical through holes are symmetrically formed in the two first sealing plates 21, and self-lubricating copper-based shaft sleeves 23 are press-fitted in the through holes.

[0041] Meanwhile, mounting holes 24 for mounting the lead screws 4 are formed at the centers of the four faces of the floating bridge body 2, and the centers of the four mounting holes 24 are on the same horizontal plane, so as to ensure that the four lead screws 4 are distributed in a cross shape.

[0042] The rotating shaft 3 is fixedly connected to the side surface of the support body 11, and a quick release structure is formed between the rotating shaft 3 and the floating bridge body 2, specifically,

[0043] A snap ring groove is formed at the free end of the rotating shaft 3, and an axial limiting snap ring 31 is mounted in the snap ring groove, and the floating bridge body 2 is limited in axial displacement after the rotating shaft 3 is inserted into the shaft sleeve 23 through the limiting snap ring 31. Meanwhile, the setting of the limiting snap ring 31 also facilitates the replacement of the rotating shaft 3, thereby improving the maintenance efficiency and further improving the use efficiency of the wet spraying platform vehicle.

[0044] Of course, the quick release structure between the rotating shaft 3 and the floating bridge body 2 is not limited to this, and other connection modes that can facilitate the installation and disassembly of the two can also be used. For example, two symmetrical through holes are formed at the free end of the rotating shaft 3 (not shown in the figure), and the floating bridge body 2 is fixed by a limiting screw after the rotating shaft 3 is inserted into the shaft sleeve 23 and the limiting screw passes through the through hole and is fixed by a nut matched therewith. Or, internal threads (not shown in the figure) or external threads (not shown in the figure) are formed at the free end of the rotating shaft 3, and the floating bridge body 2 is connected and fixed by a screw or a nut matched therewith after the rotating shaft 3 is inserted into the shaft sleeve 23.

[0045] As a further description of the above embodiment, the specific connection mode between the four cross-distributed lead screws 4 and the vehicle body longitudinal beam assembly 6 is as follows:

[0046] Two symmetrically arranged X-axis lead screw fixing plates 43 are fixed to the opposite surfaces of the two webs 62 of the vehicle body longitudinal beam assembly 6, and two symmetrically arranged Y-axis lead screw fixing plates 44 are fixed above the two upper flanges 61 of the vehicle body longitudinal beam assembly 6.

[0047] The four cross-distributed lead screws 4 include two X-axis lead screws 41 and two Y-axis lead screws 42, which are cross-distributed with an adjacent angle of 90°. One end of the four lead screws 4 is inserted into the mounting hole 24 of the floating bridge body 2 and fastened by a nut 46, and the other end is anchored on the X-axis lead screw fixing plate 43 and the Y-axis lead screw fixing plate 44 respectively and fastened by a hydraulic locking nut 45.

[0048] During installation, the four lead screws 4 are respectively inserted into the mounting hole 24 and fastened with nuts, and then the hydraulic locking nut 45 is initially screwed to the set torque using a hydraulic torque wrench. In this process, the hydraulic torque wrench is selected according to different working conditions and screwed to the corresponding target value.

[0049] In this process, the initial tightening value is determined as follows:

[0050] Pre-tightening force = 180KN × geological coefficient × tunnel structure coefficient × construction stage coefficient

[0051] Geological coefficient:

[0052] Surrounding rock grade I, geological coefficient is 1

[0053] Surrounding rock grade II, geological coefficient is 0.95

[0054] Surrounding rock grade III, geological coefficient is 0.9

[0055] Surrounding rock grade IV, geological coefficient is 0.85

[0056] Surrounding rock grade V, geological coefficient is 0.8

[0057] Tunnel structure coefficient:

[0058] Three lanes, tunnel structure coefficient is 1

[0059] Double lane, tunnel structure coefficient is 0.95

[0060] Single lane, tunnel structure coefficient is 0.9

[0061] Construction stage coefficient:

[0062] Initial support, construction stage coefficient is 1

[0063] Two lining repair, construction stage coefficient is 0.95

[0064] Initial tightening value = pre-tightening force × 70%.

[0065] In this embodiment, the cross lead screw 4 is fastened by a double-nut adjustable pre-tightening method, and a hydraulic torque wrench is matched. The pre-tightening force can be adjusted according to the working condition of the wet spraying platform car, and the adjustable range is 123-180KN.

[0066] In this embodiment, the screw rod 4 adopts a proportionally optimized fatigue-resistant design, and the ratio of the diameter to the length of the screw rod 4 is 1:8-1:10, which can improve the service life of the screw rod 4.

[0067] As a further description of the above embodiment, in order to ensure that the deflection angle of the rotating shaft 3 is ≤±4° and avoid the oversize deflection of the wet spraying trolley arm frame, thereby improving the stability and safety of the wet spraying trolley during operation, in this embodiment, a limiting assembly 5 for limiting the deflection of the rotating shaft 3 is arranged on both sides of the rotating shaft 3, which specifically comprises:

[0068] The limiting assembly 5 comprises two limiting blocks 51 and two limiting plates 54 symmetrically arranged on both sides of the rotating shaft 3, and the two limiting blocks 51 are respectively arranged on the inner sides of the two limiting plates 54.

[0069] The limiting plate 54 is an L-shaped plate, the vertical end of which is welded on the first sealing plate 21 of the floating bridge body 2, and the other end extends to both sides of the rotating shaft 3. At the same time, in order to ensure the strength of the limiting plate 54, a rib plate 55 is welded on the L-shaped inner side of the limiting plate 54.

[0070] The side wall of the support body 11 is fixedly connected with two L-shaped limiting block supports 52, and the horizontal end of the limiting block support 52 is located above the limiting plate 54. The limiting block 51 is symmetrically connected to the two limiting block supports 52 by bolts. The limiting block 51 has a hard constraint effect on the limiting plate 54, which ensures that the deflection angle of the rotating shaft 3 is ≤4° by blocking the deflection of the limiting plate 54, thereby avoiding oversize deflection and causing safety accidents.

[0071] An emergency stop button (not shown in the figure) is arranged on the side wall opposite to the limiting plate 54 of the limiting block 51, and the emergency stop button is electrically connected with the working arm rotation control system. When the rotating shaft 3 drives the limiting plate 54 to contact the limiting block 51, the emergency stop button is pressed, and the system automatically stops the rotation of the working arm.

[0072] At the same time, two symmetrically arranged distance sensors 53 are also connected to the two limiting block supports 52, which are used to detect the distance between the limiting plate 54 and the limiting block 51, and have a soft limiting effect. When the limiting plate 54 deflects to the right with the floating bridge body 2, the distance between the left limiting plate 54 and the left sensor 53 will be shortened; when the limiting plate 54 deflects to the left with the floating bridge body 2, the distance between the right limiting plate 54 and the right sensor 53 will be shortened.

[0073] The sensor 53 is electrically connected with an alarm (not shown in the figure), and the sensor 53 is electrically connected with the working arm rotation control system. When the sensor 53 detects that the deflection angle of the rotating shaft 3 is ±3°, the sensor 53 detects the limiting plate 54, the alarm gives an alarm, and at the same time, the working arm rotation control system automatically reduces the rotation speed of the working arm.

[0074] The installation position of the limiting block 51 and the sensor 53 is determined according to the deflection displacement generated when the floating bridge body 2 is rotated by the rotating shaft 3, specifically,

[0075] The horizontal included angle between the outer wall of the limiting block 51 and the inner wall of the limiting plate 54 is 4°, and the horizontal included angle between the center of the emitting end of the sensor 53 and the inner wall of the limiting plate 54 is 3°. When the limiting plate 54 deflects by 3°, the sensor 53 just detects the limiting plate 54; when the limiting plate 54 deflects by 4°, the limiting plate 54 just contacts the limiting block 51.

[0076] Therefore, the limiting principle of the limiting plate 54 and the limiting block 51 is as follows:

[0077] When the concrete wet spraying trolley tunnel large section is operated, the telescopic arm is elongated, the arm frame-nozzle system generates an overturning moment, the rotating table 1 is subjected to a torsion, the torsion is transferred to the floating bridge body 2 through the rotating shaft 3, the floating bridge body is slightly rotated under the constraint of the cross-shaped lead screw 4, at this time, the limiting block 51 on the side surface of the supporting body 11 is fixed, and the limiting plate 54 rotates with the floating bridge body 2. When the limiting plate 54 rotates, a deflection angle is generated, and the distance to the limiting block 51 is shortened. When the limiting plate 54 deflects ±3° with the floating bridge body 2, the sensor 53 detects the limiting plate 54, the system starts to alarm, and the rotating speed of the working arm is automatically reduced; when the limiting plate 54 deflects ±4° with the floating bridge body 2, the limiting plate 54 contacts the limiting block 51, at this time, the system automatically stops the rotation of the working arm.

[0078] Wherein, ± respectively represent that the limiting plate 54 deflects right and left with the floating bridge body 2.

[0079] In the embodiment, the limiting block 51 is a detachable quenched steel block, and the curvature radius of the working surface matches the contact surface of the rotating shaft 3.

[0080] In summary, the floating bridge body and the cross-shaped lead screw in the application can make the stress of the vehicle frame uniformly distributed, and improve the torsional resistance of the vehicle body; at the same time, the double protection of the limiting block and the sensor can reduce the vibration amplitude of the vehicle body, and achieve the effect of preventing the vehicle body from overturning. Therefore, the application effectively overcomes the shortcomings in the prior art and has high industrial utilization value.

[0081] The above embodiments only exemplarily illustrate the principle and effect of the application, and are not used to limit the application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the application should be covered by the claims of the application.

Claims

1. A torsion-resistant floating bridge structure for a concrete spraying trolley, comprising a vehicle body longitudinal beam component (6), a turntable (1) being fixedly connected to the vehicle body longitudinal beam component (6), and characterized in that: The side wall of the turntable (1) is fixedly connected to a rotating shaft (3), and the suspended end of the rotating shaft (3) is rotatably connected to the floating bridge body (2). The floating bridge body (2) is provided with four cross-distributed screws (4), one end of the four screws (4) is detachably connected to the floating bridge body (2), and the other end is adjustably connected to the vehicle body longitudinal beam assembly (6) through a connecting assembly. A limiting assembly (5) for limiting the deflection angle of the rotating shaft (3) is provided between the turntable (1) and the floating bridge body (2).

2. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 1 is characterized in that: The floating bridge body (2) comprises two first sealing plates (21) arranged in parallel, the two first sealing plates (21) are welded to form a rectangular cavity via a second sealing plate (22), and through holes are symmetrically opened on the two first sealing plates (21), and shaft sleeves (23) are press-fitted into the through holes.

3. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 1, characterized in that: The floating bridge body (2) is provided with mounting holes (24) on all four sides, and the centers of the four mounting holes (24) are on the same horizontal plane.

4. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 2, characterized in that: A snap ring groove is provided at the suspended end of the rotating shaft (3) and an axial limiting snap ring (31) is installed. After the rotating shaft (3) is inserted into the shaft sleeve (23), the axial displacement of the floating bridge body (2) is limited by the limiting snap ring (31).

5. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 3, characterized in that: The connecting assembly comprises two X-axis screw fixing plates (43) and two Y-axis screw fixing plates (44), wherein the two X-axis screw fixing plates (43) are symmetrically fixed between the vehicle body longitudinal beam components (6), and the two Y-axis screw fixing plates (44) are fixed to the upper surface of the vehicle body longitudinal beam components (6).

6. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 5, characterized in that: The lead screw (4) comprises two X-axis lead screws (41) and two Y-axis lead screws (42), one end of each of the X-axis lead screw (41) and the Y-axis lead screw (42) is inserted into the mounting hole (24) and tightened by a nut (46), and the other end is respectively fixed on the X-axis lead screw fixing plate (43) and the Y-axis lead screw fixing plate (44) and tightened by a hydraulic locking nut (45).

7. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 2, characterized in that: The limiting assembly (5) comprises two limiting blocks (51) and two limiting plates (54) symmetrically arranged on both sides of the rotating shaft (3); the two limiting blocks (51) are respectively arranged on the inner sides of the two limiting plates (54); the two limiting blocks (51) are fixed to the side walls of the turntable (1) through limiting block brackets (52); one end of the two limiting plates (54) is connected to the side wall of the first sealing plate (21), and the other end is suspended in the air.

8. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 7, characterized in that: A sensor (53) for detecting the deflection angle of the limiting plate (54) is also installed on the limiting block bracket (52).

9. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 7, characterized in that: The limiting block (51) is detachably connected to the lower surface of the limiting block bracket (52), and the horizontal angle between the outer wall of the limiting block (51) and the inner wall of the limiting plate (54) is 4°.

10. The torsion-resistant floating bridge structure for a concrete spraying trolley according to claim 8, characterized in that: The horizontal angle between the center of the transmitting end of the sensor (53) and the inner wall of the limiting plate (54) is 3°.

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