Bridge anti-seepage detection device in bridge engineering

Abstract

The invention discloses a bridge water seepage prevention detection device in bridge engineering, and relates to the technical field of bridge engineering, the bridge water seepage prevention detection device comprises a main body, the top of the main body is provided with an arch-shaped frame, the arch-shaped frame is rotatably provided with a main shaft, the outer wall of the main shaft is correspondingly provided with an expansion part, one side of the expansion part is fixedly provided with a fixed rod through welding, and the fixed rod is fixedly provided with a through hole. A plurality of attaching pieces are movably arranged on the outer wall of the fixing rod, water-absorbent resin is installed at the tops of the attaching pieces, a plurality of liquid sensors are installed at the top of the main body in a linear arrangement mode, the surface contours of the liquid sensors are matched with the outer contours of the attaching pieces, and a drying machine is installed on one side of the top of the main body. An impurity removing seat is installed on the other side of the top of the main body, bearing sleeves are installed on the outer wall of a fixing rod in a linear arrangement mode, a plurality of elastic pieces are installed on the inner wall of an attaching piece in a circumferential mode, and the device has the advantage of being accurate in detection.

Description

Technical Field

[0001] The invention relates to the technical field of bridge engineering, and in particular to a bridge anti-seepage detection device in bridge engineering. Background Art

[0002] The expansion joints of bridges are often subjected to the violent impact of wheel loads and are exposed to the natural environment for a long time without protection, which may cause cracks and damage to waterstops. Rain, snow and surface water will penetrate into the bridge structure through the damaged expansion joints, corrode the reinforced concrete and affect the quality, safety and service life of the bridge.

[0003] Bridges may settle or deform during use, especially when the foundation is uneven or the soil conditions are poor. This settlement and deformation will affect the geometry of the expansion joint, causing an uneven bottom surface. Existing instruments for detecting water seepage can only detect in a plane, lacking the ability to accurately detect the leakage location. Therefore, it is necessary to design a bridge anti-seepage detection device for bridge engineering with accurate detection. Summary of the invention

[0004] The purpose of the present invention is to provide a bridge anti-seepage detection device in bridge engineering to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a bridge anti-seepage detection device in a bridge project, comprising a main body, an arch frame is installed on the top of the main body, a main shaft is rotatably installed on the arch frame, an expansion part is correspondingly installed on the outer wall of the main shaft, a fixing rod is fixedly installed on one side of the expansion part by welding, a plurality of bonding sheets are movably provided on the outer wall of the fixing rod, a water-absorbing resin is installed on the top of the bonding sheet, a plurality of liquid sensors are installed in a straight line on the top of the main body, the surface contour of the liquid sensor is adapted to the outer contour of the bonding sheet, a motor is installed on one side of the arch frame, and the output end of the motor is connected to the main shaft. When it is necessary to judge the water seepage at the bottom of the expansion joint of the bridge, the main body is placed in the middle position of the bottom of the expansion joint of the bridge, so that the motor drives the main shaft to rotate, and drives the fitting sheet to move to the bottom of the expansion joint of the bridge, and the water-absorbing resin on the top fits with the bottom contour. Since the bottom contour is uneven, multiple movable fitting sheets can fit more closely to the bottom of the expansion joint of the bridge, so that the water-absorbing resin can contact the water-seeping gap. The water-absorbing resin will absorb water when encountering the water-seeping crack. When it rotates to the liquid sensor directly below, it can detect the liquid content, thereby judging whether there is water seepage at the current position.

[0006] According to the above technical solution, a dryer is installed on one side of the top of the main body, and a dust removal seat is installed on the other side of the top of the main body. When the main shaft drives the bonding sheet to rotate to a position flush with the dryer, the water-absorbing resin on the bonding sheet is dried by the dryer to facilitate the detection of water seepage at the next position, and when the main shaft drives the bonding sheet to rotate to a position flush with the dust removal seat, the dust removal seat removes stones and gravels adhered to the water-absorbing resin on the surface of the bonding sheet, and only retains the water absorbed by the water-absorbing resin.

[0007] According to the above technical solution, the outer wall of the fixing rod is linearly arranged with a bearing sleeve, and the inner wall of the bonding sheet is circumferentially arranged with a plurality of elastic members, and one end of the elastic member is in contact with the outer wall of the bearing sleeve. When the bonding sheet is pressed against the bottom surface of the expansion joint, the bonding sheet will be pressed downward, and the elastic member above will be contracted, and the elastic member below will be stretched, while the bonding sheet that is not subjected to the squeezing force will still maintain the previous height. When removed, due to the elastic recovery effect of the elastic member, each bonding sheet can be neatly returned to its original position.

[0008] According to the above technical solution, the side wall of the bonding sheet is evenly installed with a plurality of connection blocks, one end of the connection block is connected with an elastic wire, and one end of the elastic wire is fixedly connected to the outer wall of the fixing rod. When the bonding sheet contacts the bottom surface of the expansion joint, due to the existence of friction, when the bonding sheet moves to the topmost interval, it will stick to the bottom surface and roll at a certain angle, at which time the elastic wire will be pulled to stretch it. When the elastic wire is stretched, it will store energy, and when the bonding sheet moves to a point where it is no longer in contact with the bottom surface of the expansion joint, it will return to the original angle, so that the water-absorbing resin can always return to the middle angle, which is convenient for detecting the liquid content.

[0009] According to the above technical solution, one side of the impurity removal seat is arc-shaped and matches the outer contour of the bonding sheet. One side of the impurity removal seat is evenly provided with a plurality of installation grooves. The inner wall of the installation groove is slidably plugged with a cleaning brush. One end of each installation groove extends inward to provide an inner flow channel. The plurality of inner flow channels are interconnected and connected. When the bonding sheet rotates to the middle position, since there are a lot of dirt such as sand and gravel on the bottom surface of the expansion joint, it will affect the accuracy of the liquid content detection. Therefore, when it rotates to the cleaning brush, the surface of the absorbent resin is scrubbed with the cleaning brush to remove the dirt on the surface. The cleaning brush can slide in the installation groove. When the liquid pressure in the installation groove increases, the cleaning brush will extend outward. When the liquid pressure decreases, the cleaning brush will retract inward, so as to facilitate the adjustment of the cleaning force on the surface of the bonding sheet.

[0010] According to the above technical solution, a square shell is fixedly installed on one side of the top of the main body, a ratchet is rotatably installed on the inner wall of the square shell, and inclined support arms are rotatably installed at the centers of both sides of the ratchet, a spring is fixedly installed on one end of the inclined support arm, a clamping block is rotatably provided on the inclined support arm, one end of the spring is in contact with the clamping block, and the clamping block is meshed with the ratchet, piston plates are slidably installed on the inner walls of both sides of the square shell, and liquid pipes are through-connected at both ends of the square shell, and one end of the liquid pipe is through-connected with the inner flow channel. When the angle of the inclined support arm changes in the parallel direction, the piston plates will be squeezed to both sides. When the main shaft rotates normally in the forward direction, the water seepage detection work is carried out normally, which will drive the ratchet to rotate counterclockwise. At this time, the angle of the inclined support arm remains unchanged, the position of the piston plate remains unchanged, and the cleaning brush still maintains its original position. When the cleaning brush has not completely removed the gravel on the water-absorbing resin, the bonding sheet will encounter resistance when moving to the liquid sensor at the bottom. Due to the reaction force, the main shaft will be squeezed in the opposite direction by a certain angle. At this time, the main shaft will drive the ratchet to reverse, and the angle of the inclined support arm is driven by the card block to change. The angle of the inclined support arm moves to a parallel position, squeezing the two piston plates outward, squeezing the liquid in the square shell into the liquid pipe and into the inner flow channel, so that the liquid pressure in the mounting groove is increased, and the cleaning brush is squeezed outward. The cleaning brush can fit the water-absorbing resin more closely for cleaning, which is convenient for automatically adjusting the cleaning force when encountering resistance; at this time, the driving motor rotates in the opposite direction, so that the cleaning brush cleans the bonding sheet again.

[0011] According to the above technical solution, one end of the spindle extends into the inner wall of the square housing, one end of the spindle movably penetrates the oblique support arm, and is connected to the rotation center of the ratchet wheel through a sliding key, and the main body is composed of two left and right parts, and an electric telescopic rod is connected between the left and right parts. When the piston plate needs to be restored to its original position, the electric telescopic rod is started to stretch it, which will separate the left and right parts of the main body. At this time, the end of the spindle will be separated from the ratchet, and the ratchet wheel can rotate freely without hindrance. At this time, the cleaning brush is manually squeezed to the appropriate position of the installation groove, and then the left and right parts of the main body are combined. At this time, the spindle is reconnected to the ratchet wheel, which is convenient for manual adjustment of the position of the cleaning brush.

[0012] According to the above technical solution, multiple arms are installed around the main body through hinges, one end of the arm is installed with an electric propeller, and negative pressure pipes are installed on both sides of the main body. A vacuum suction cup is installed at one end of the negative pressure pipe, and a vacuum pump is connected to the other end of the negative pressure pipe. The connection part between the vacuum pump and the negative pressure pipe is a sliding plug-in fit. Negative pressure is introduced into the vacuum suction cup through the vacuum pump, and the vacuum suction cup is attached to the bottom surface of the bridge next to the expansion joint, which is convenient for fixed position water seepage detection. The entire main body is controlled to fly through the electric propeller, which is convenient for flying to the expansion joint position for detection, and vacuum adsorption is started when flying to the position.

[0013] Compared with the prior art, the beneficial effect achieved by the present invention is that: by providing a plurality of bonding sheets, when the bonding sheets are used to detect whether there is water seepage at the bottom of the bridge expansion joint, since the positions of each bonding sheet are independent, each bonding sheet can be made to fit the bottom of the bridge expansion joint as much as possible after extrusion, thereby facilitating the detection of the specific location of water seepage. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a schematic diagram of the installation of the vacuum pump of the present invention; Figure 3 It is a schematic diagram of the installation of the square housing of the present invention; Figure 4 is a schematic diagram of the cross-sectional structure of the bonding sheet of the present invention; Figure 5 is a schematic diagram of the front view structure of the bonding sheet of the present invention; Figure 6 It is a schematic diagram of the internal structure of the square housing of the present invention; Figure 7 It is a working principle diagram of the present invention; 1. Main body; 11. Support arm; 12. Electric propeller; 13. Vacuum suction cup; 14. Negative pressure pipe; 15. Vacuum pump; 16. Electric telescopic rod; 2. Dryer; 3. De-impurity seat; 31. Liquid pipe; 32. Square shell; 321. Piston plate; 322. Ratchet; 323. Oblique support arm; 324. Block; 325. Spring; 33. Cleaning brush; 34. Mounting groove; 35. Inner flow channel; 4. Arch frame; 41. Main shaft; 42. Laminating sheet; 43. Expansion part; 421. Fixed rod; 422. Elastic wire; 423. Elastic part; 424. Bearing sleeve; 425. Connecting block; 426. Water-absorbing resin; 5. Liquid sensor; 88. Motor. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] See also Figure 1-Figure 7The present invention provides a technical solution: a bridge anti-seepage detection device in a bridge project, comprising a main body 1, an arch frame 4 is installed on the top of the main body 1, a main shaft 41 is rotatably installed on the arch frame 4, an expansion part 43 is correspondingly installed on the outer wall of the main shaft 41, a fixing rod 421 is fixedly installed on one side of the expansion part 43 by welding, a plurality of bonding sheets 42 are movably arranged on the outer wall of the fixing rod 421, a water-absorbing resin 426 is installed on the top of the bonding sheet 42, a plurality of liquid sensors 5 are installed in a straight line on the top of the main body 1, the surface contour of the liquid sensor 5 is adapted to the outer contour of the bonding sheet 42, a motor 88 is installed on one side of the arch frame 4, and the output end of the motor 88 is connected to the main shaft 41. When it is necessary to determine whether there is water seepage at the bottom of a bridge expansion joint, the main body 1 is placed in the middle of the bottom of the bridge expansion joint, so that the motor 88 drives the main shaft 41 to rotate, driving the bonding sheet 42 to move to the bottom of the bridge expansion joint, and the water-absorbing resin 426 on the top is fitted with the bottom contour. Since the bottom contour is uneven, multiple movably arranged bonding sheets 42 can be more closely fitted to the bottom of the bridge expansion joint, so that the water-absorbing resin 426 can contact the water-seeping gaps. The water-absorbing resin 426 will absorb water when encountering water-seeping cracks. When it rotates to the liquid sensor 5 directly below, it can detect the liquid content, thereby determining whether there is water seepage at the current position.

[0017] A dryer 2 is installed on one side of the top of the main body 1, and a dust removal seat 3 is installed on the other side of the top of the main body 1. When the main shaft 41 drives the bonding sheet 42 to rotate to a position flush with the dryer 2, the water-absorbing resin 426 on the bonding sheet 42 is dried by the dryer 2 to facilitate the detection of water seepage at the next position. When the main shaft 41 drives the bonding sheet 42 to rotate to a position flush with the dust removal seat 3, the dust removal seat 3 removes stones and gravels adhered to the water-absorbing resin 426 on the surface of the bonding sheet 42, and only retains the water absorbed by the water-absorbing resin 426.

[0018] The outer wall of the fixing rod 421 is linearly arranged with bearing sleeves 424, and the inner wall of the bonding sheet 42 is circumferentially arranged with multiple elastic members 423, and one end of the elastic member 423 is in contact with the outer wall of the bearing sleeve 424. When the bonding sheet 42 is pressed to the bottom surface of the expansion joint, the bonding sheet 42 will be pressed downward, and the elastic member 423 above will be contracted, and the elastic member 423 below will be stretched, while the bonding sheet 42 that is not subjected to the squeezing force will still maintain the previous height. When removed, due to the elastic recovery effect of the elastic member 423, each bonding sheet 42 can be neatly returned to its original position.

[0019] The side wall of the bonding sheet 42 is evenly installed with a plurality of connection blocks 425, one end of the connection block 425 is connected to an elastic wire 422, and one end of the elastic wire 422 is fixedly connected to the outer wall of the fixing rod 421. When the bonding sheet 42 contacts the bottom surface of the expansion joint, due to the existence of friction, when the bonding sheet 42 moves to the topmost interval, it will stick to the bottom surface and roll at a certain angle, at which time the elastic wire 422 will be pulled to stretch it, and the elastic wire 422 will store energy when being stretched, and will return to the original angle when the bonding sheet 42 moves to a point where it is not in contact with the bottom surface of the expansion joint, so that the water-absorbing resin 426 can always return to the most middle angle, which is convenient for detecting the liquid content.

[0020] One side of the impurity removal seat 3 is arc-shaped and matches the outer contour of the bonding sheet 42. One side of the impurity removal seat 3 is evenly provided with multiple installation grooves 34. The inner wall of the installation groove 34 is slidably plugged with a cleaning brush 33. One end of each installation groove 34 extends inward to provide an inner flow channel 35. Multiple inner flow channels 35 are mutually connected and converged. When the bonding sheet 42 rotates to the middle position, since there are a lot of dirt such as sand and gravel on the bottom surface of the expansion joint, it will affect the accuracy of liquid content detection. Therefore, when it rotates to the cleaning brush 33, the surface of the water-absorbing resin 426 is scrubbed with the cleaning brush 33 to remove the dirt on the surface. The cleaning brush 33 can slide in the installation groove 34. When the liquid pressure in the installation groove 34 increases, the cleaning brush 33 will extend outward. When the liquid pressure decreases, the cleaning brush 33 will be retracted inward, which is convenient for adjusting the cleaning force on the surface of the bonding sheet 42.

[0021] A square shell 32 is fixedly installed on one side of the top of the main body 1, and a ratchet 322 is rotatably installed on the inner wall of the square shell 32, and oblique support arms 323 are rotatably installed at the centers of both sides of the ratchet 322, and a spring 325 is fixedly installed on one end of the oblique support arm 323, and a clamping block 324 is rotatably provided on the oblique support arm 323, one end of the spring 325 contacts the clamping block 324, and the clamping block 324 and the ratchet 322 are meshed with each other, and piston plates 321 are slidably installed on the inner walls of both sides of the square shell 32, and both ends of the square shell 32 are through-connected with liquid pipes 31, and one end of the liquid pipe 31 is through-connected with the inner flow channel 35. When the angle of the inclined arm 323 changes in the parallel direction, the piston plate 321 will be squeezed to both sides. When the main shaft 41 rotates normally in the forward direction, the water seepage detection work is carried out normally, which will drive the ratchet 322 to rotate counterclockwise. At this time, the angle of the inclined arm 323 remains unchanged, the position of the piston plate 321 remains unchanged, and the cleaning brush 33 still maintains its original position. When the cleaning brush 33 does not completely remove the gravel on the water-absorbing resin 426, the bonding sheet 42 will encounter resistance when it moves to the liquid sensor 5 at the bottom. Due to the reaction force, the main shaft 41 will be squeezed in the opposite direction by a certain angle. At this time, the main shaft 4 1 will drive the ratchet wheel 322 to reverse, and use the block 324 to drive the angle of the inclined support arm 323 to change. The angle of the inclined support arm 323 moves to a parallel position, pressing the two piston plates 321 outward, squeezing the liquid in the square shell 32 into the liquid pipe 31 and into the inner flow channel 35, so that the liquid pressure in the installation groove 34 is increased, and the cleaning brush 33 is pressed outward, so that the cleaning brush 33 can fit the water-absorbing resin 426 more closely for cleaning, and it is convenient to automatically adjust the cleaning force when encountering resistance; at this time, the driving motor 88 rotates in the opposite direction, so that the cleaning brush 33 cleans the bonding sheet 42 again.

[0022] One end of the main shaft 41 extends into the inner wall of the square housing 32, and one end of the main shaft 41 movably passes through the oblique support arm 323, and is connected to the rotation center of the ratchet 322 through a sliding key. The main body 1 is composed of two left and right parts, and the electric telescopic rod 16 is connected between the left and right parts. When the piston plate 321 needs to be restored to its original position, the electric telescopic rod 16 is started to stretch it, which will separate the left and right parts of the main body 1. At this time, the end of the main shaft 41 will be separated from the ratchet 322, and the ratchet 322 can rotate freely without hindrance. At this time, the cleaning brush 33 is manually squeezed to the appropriate position of the installation groove 34, and then the left and right parts of the main body 1 are combined. At this time, the main shaft 41 is reconnected with the ratchet 322, which is convenient for manual adjustment of the position of the cleaning brush 33.

[0023] A plurality of arms 11 are movably mounted around the main body 1 through hinges, and an electric propeller 12 is mounted at one end of the arm 11. Negative pressure pipes 14 are mounted on both sides of the main body 1, and a vacuum suction cup 13 is mounted at one end of the negative pressure pipe 14. A vacuum pump 15 is connected to the other end of the negative pressure pipe 14, and the connection between the vacuum pump 15 and the negative pressure pipe 14 is a sliding plug-in fit. Negative pressure is introduced into the vacuum suction cup 13 through the vacuum pump 15, and the vacuum suction cup 13 is attached to the bottom surface of the bridge next to the expansion joint, which is convenient for fixed position water seepage detection. The entire main body 1 is controlled to fly through the electric propeller 12, which is convenient for flying to the expansion joint position for detection, and vacuum adsorption is started when flying to the position.

[0024] By providing a plurality of bonding sheets 42, when the bonding sheets 42 detect whether there is water seepage at the bottom of the bridge expansion joint, since the positions of each bonding sheet 42 are independent, each bonding sheet 42 can be made to fit the bottom of the bridge expansion joint as much as possible after extrusion, thereby facilitating the detection of the specific location of the water seepage.

[0025] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0026] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A bridge anti-seepage detection device in a bridge project, comprising a main body (1), characterized in that: An arch frame (4) is installed on the top of the main body (1), a main shaft (41) is rotatably installed on the arch frame (4), an expansion portion (43) is correspondingly installed on the outer wall of the main shaft (41), a fixing rod (421) is fixedly installed on one side of the expansion portion (43) by welding, a plurality of bonding sheets (42) are movably provided on the outer wall of the fixing rod (421), a water-absorbing resin (426) is installed on the top of the bonding sheet (42), a plurality of liquid sensors (5) are installed in a straight line on the top of the main body (1), the surface contour of the liquid sensor (5) is adapted to the outer contour of the bonding sheet (42), a motor (88) is installed on one side of the arch frame (4), and an output end of the motor (88) is connected to the main shaft (41).

2. The anti-water seepage detection device for bridge engineering according to claim 1, characterized in that: A dryer (2) is installed on one side of the top of the main body (1), and a debris removal seat (3) is installed on the other side of the top of the main body (1).

3. The anti-water seepage detection device for bridge engineering according to claim 2, characterized in that: The outer wall of the fixing rod (421) is provided with bearing sleeves (424) arranged in a straight line, and the inner wall of the bonding sheet (42) is provided with a plurality of elastic members (423) arranged in a circle, and one end of the elastic member (423) is in contact with the outer wall of the bearing sleeve (424).

4. The anti-water seepage detection device for bridge engineering according to claim 3, characterized in that: A plurality of connection blocks (425) are evenly mounted on the side wall of the bonding sheet (42), one end of the connection block (425) is connected to an elastic thread (422), and one end of the elastic thread (422) is fixedly connected to the outer wall of the fixing rod (421).

5. The anti-water seepage detection device for bridge engineering according to claim 4, characterized in that: One side of the impurity removal seat (3) is arc-shaped and matches the outer contour of the bonding sheet (42); a plurality of mounting grooves (34) are evenly formed on one side of the impurity removal seat (3); a cleaning brush (33) is slidably inserted into the inner wall of the mounting groove (34); one end of each mounting groove (34) extends inwardly to form an inner flow channel (35); and the plurality of inner flow channels (35) are interconnected and convergently connected.

6. The anti-water seepage detection device for bridge engineering according to claim 5, characterized in that: A square housing (32) is fixedly mounted on one side of the top of the main body (1); a ratchet (322) is rotatably mounted on the inner wall of the square housing (32); oblique support arms (323) are rotatably mounted at the centers of both sides of the ratchet (322); a spring (325) is fixedly mounted on one end of the oblique support arm (323); a clamping block (324) is rotatably mounted on the oblique support arm (323); one end of the spring (325) is in contact with the clamping block (324); the clamping block (324) and the ratchet (322) are meshed with each other; piston plates (321) are slidably mounted on the inner walls of both sides of the square housing (32); both ends of the square housing (32) are connected through a liquid pipeline (31); one end of the liquid pipeline (31) is connected through an inner flow channel (35).

7. The anti-water seepage detection device for bridge engineering according to claim 6, characterized in that: One end of the main shaft (41) extends into the inner wall of the square housing (32), one end of the main shaft (41) movably passes through the oblique support arm (323), and is connected to the rotation center of the ratchet wheel (322) via a sliding key. The main body (1) is composed of two left and right parts, and an electric telescopic rod (16) is connected between the left and right parts.

8. The anti-water seepage detection device for bridge engineering according to claim 7, characterized in that: A plurality of arms (11) are movably mounted on the periphery of the main body (1) via hinges, one end of each arm (11) being mounted with an electric propeller (12), negative pressure pipes (14) being mounted on corresponding sides of the main body (1), one end of each negative pressure pipe (14) being mounted with a vacuum suction cup (13), and the other end of each negative pressure pipe (14) being connected to a vacuum pump (15), the connection between the vacuum pump (15) and the negative pressure pipe (14) being a sliding plug-in fit.

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