A blocking device for mud and water inrush in tunnels

Abstract

The present invention relates to the technical field of tunnel construction, and discloses a blocking device for sudden mud and water gushing in tunnels, comprising a double blocking mechanism, wherein the double blocking mechanism comprises a base, a freely rotatable blocking plate is provided on the base, vertical frames are provided on both sides of the top of the base, the vertical frames are fitted with the side walls of the tunnel, and blocking doors are hingedly provided on the inner sides of the vertical frames, and the blocking plate and the blocking door constitute a double blocking defense line, and a float and a hood are further provided in the base, the float is connected to the blocking plate by a steel rope, and the float pulls the blocking plate to rotate by buoyancy, and the hood is connected to the blocking door by a steel rope, and the hood pulls the blocking door to automatically close under the impact of water flow, and a drainage system is provided in the base, so that the device realizes the function of blocking and buffering sudden mud and water gushing, and compared with a retaining wall with a fixed structure, the device does not affect normal construction operations, can automatically open two blocking mechanisms, thereby buying time for personnel evacuation and improving the probability of survival.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, in particular to a device for blocking sudden mud and water gushing in tunnels. Background Art

[0002] Existing methods and measures for preventing and controlling mud and water inrush include draining aquifers, reducing pressure, draining old holes, diverting rivers, and preventing seepage. Water inrush channel management involves constructing anti-seepage curtains and walls, retaining water-blocking pillars, using local grouting to address water inrush points, and filling and plugging subsidence. Advanced water exploration guides construction, and measures such as waterproof gates and retaining walls are employed.

[0003] During the tunnel excavation construction process, sudden mud and water bursts cause a higher casualty rate than preventive construction water bursts. The main reason is that the water flow speed and flow rate are relatively large when mud and water bursts occur, and the damage caused to the evacuated personnel by the impact of the water flow, as well as the collision damage caused by being swept by the water flow. Due to the suddenness of mud and water bursts, the time given to construction personnel to evacuate and build waterproof doors and retaining walls is short, and effective protection cannot be formed. It is also impossible to erect waterproof doors and retaining walls directly on the construction channel during normal construction. Therefore, in the face of sudden mud and water bursts, how to build preventive automatic water retaining equipment without affecting normal construction operations is an effective guarantee to extend the evacuation time and increase the success rate of evacuation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above difficulties and provide a blocking device for sudden mud and water gushing in tunnels.

[0005] To solve the above technical problems, the present invention provides a technical solution: a device for blocking mud and water inrush in a tunnel, comprising a double blocking mechanism, which is arranged between the excavation section and the construction section. The double blocking mechanism comprises a base, on which is provided a freely rotatable blocking plate, and vertical frames provided on both sides of the top of the base, which are in contact with the tunnel sidewalls. The vertical frames are hingedly provided with blocking doors on the inner sides thereof, and the blocking plates and the blocking doors form a double blocking defense line.

[0006] The base is also equipped with a float and a hood. The float is connected to the blocking plate by a steel rope. The float relies on buoyancy to pull the blocking plate to rotate. The hood is connected to the blocking door by a steel rope. Driven by the impact of water flow, the hood pulls the blocking door to close automatically. A drainage system is provided in the base.

[0007] As an improvement: the blocking plate includes a sleeve, a flat plate and multiple counterweights are provided on both sides of the sleeve, a rotating shaft is provided inside the base and the shaft rotates with the sleeve, multiple straight rods are provided on the front side of the flat plate, and gaps are left between adjacent straight rods. The center of gravity of the blocking plate is close to the rotating shaft and biased toward the flat plate.

[0008] As an improvement: the drainage system includes a drainage chamber inside the base, the drainage chamber is located below the straight rod, drainage channels are provided on both sides of the drainage chamber, the drainage channels are connected to the drainage trough at the construction section, the float is placed in the drainage chamber, and the hood is stored in the groove at the bottom of the drainage chamber.

[0009] As an improvement: the front side of the drainage chamber is provided with a supporting platform that cooperates with the straight rod, the rear side of the drainage chamber is provided with an inclined platform, the inclined platform is provided with a supporting platform that cooperates with the flat plate, and multiple vertical plates are provided behind the inclined platform. The counterweight block is located in the gap between the vertical plates, and a protective plate is provided on the top of the vertical plate. The protective plate is located above the counterweight block. The counterweight block cooperates with the rear side of the inclined platform. A floater is provided in the internal groove of the support platform. The floater includes a buoyancy plate. A top plate is provided on the top of the buoyancy plate. The top plate passes through the through hole on the top of the support platform and cooperates with the flat plate, and the top plate cooperates with the blocking door limit.

[0010] As an improvement: the drainage system also includes a drainage trough on the inclined platform, the drainage trough is connected to the drainage cavity and the cavity at the bottom of the protective plate, and when the blocking plate is erected, there is a gap between the blocking plate and the protective plate.

[0011] As an improvement: air bags are provided in the grooves on both sides of the plurality of straight rods. When the air bags are inflated, adjacent air bags are squeezed and the air bags on the sides are in contact with the stand.

[0012] As an improvement: a water pressure detector is provided on the flat plate, and one of the counterweights is replaced by a start switch, which provides a start signal for airbag inflation. The start switch includes a transparent cover, a closed cavity inside the transparent cover, and a sliding rod is obliquely provided in the closed cavity. When the blocking plate is in a horizontal state, the end of the sliding rod close to the shaft sleeve is lower than the end away from the shaft sleeve. A slip ring is provided for sliding on the end of the sliding rod close to the shaft sleeve, and a fixed platform is provided on the end of the sliding rod away from the shaft sleeve. Both the slip ring and the fixed platform are provided with matching contacts.

[0013] As an improvement: a placement groove is provided on the rear side of the blocking door, an impact plate is hingedly provided in the placement groove, a storage groove is provided on the inner side of the impact plate, the boss inside the storage groove is connected to the placement groove by a steel rope, the top and bottom of the inner side of the impact plate are provided with connecting covers, the connecting covers are connected to the placement groove, and a rib plate connected to the base is provided on the rear side of the stand.

[0014] As an improvement: hollow rods are provided at the upper and lower ends of the hood, the two hollow rods are connected to the outer sides of the two impact plates through steel ropes, and the lower hollow rod is connected to the base through an elastic rope.

[0015] Compared with the prior art, the present invention has the following advantages: the present device can block and buffer sudden mud and water surges. Compared with fixed retaining walls, the present device does not affect normal construction operations and can automatically open two blocking mechanisms, thereby buying time for personnel evacuation and increasing the probability of survival. Specifically:

[0016] This device does not use electric equipment, but relies on buoyancy and water flow impact to drive the opening of the blocking mechanism, avoiding the problem of the electric blocking device going out of service when the water inrush tunnel is powered off, thereby improving reliability;

[0017] The first line of defense is constructed by the blocking plate. The blocking plate is placed flat on the base without affecting the normal passage of construction vehicles. The blocking plate is automatically erected by the buoy and floater to block the impact of the sudden water.

[0018] The blocking door is used to build a second line of defense to deal with explosive mud and water surges. The hood and impact plate will automatically close the blocking door under the impact of the water flow, blocking the huge impact of the sudden water surge and thus buying time for evacuation.

[0019] The drainage system has multiple drainage channels, which can drain accumulated water, reduce water pressure, and change flow direction to meet daily drainage needs. In the event of a sudden water burst, it can protect the blocking plate and blocking door by draining water and relieving pressure. By changing the direction of water flow, it can reduce the impact of water flow and ensure the safety of personnel evacuation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of a tunnel mud and water gushing blocking device of the present invention. Figure 1 .

[0021] Figure 2 This is a schematic diagram of the structure of a tunnel mud and water gushing blocking device of the present invention. Figure 2 .

[0022] Figure 3 It is a structural schematic diagram of the installation state of a blocking device for sudden mud and water gushing in a tunnel according to the present invention.

[0023] Figure 4 It is a structural schematic diagram of the blocking state of a blocking device for sudden mud and water gushing in a tunnel according to the present invention.

[0024] Figure 5 It is a structural schematic diagram of the base of a blocking device for mud and water inrush in a tunnel according to the present invention.

[0025] Figure 6 This is a cross-sectional view of the base of a device for blocking mud and water inrush in a tunnel according to the present invention. Figure 1 .

[0026] Figure 7 This is a cross-sectional view of the base of a device for blocking mud and water inrush in a tunnel according to the present invention. Figure 2 .

[0027] Figure 8 The present invention is a schematic structural diagram of a blocking plate of a blocking device for preventing sudden mud and water gushing in tunnels.

[0028] Figure 9The present invention is a cross-sectional view of a start switch of a blocking device for preventing sudden mud and water inrush in a tunnel.

[0029] Figure 10 It is a schematic diagram of the internal structure of a base of a blocking device for sudden mud and water gushing in a tunnel according to the present invention.

[0030] Figure 11 The present invention is a schematic structural diagram of a stand and a blocking door of a blocking device for preventing sudden mud and water gushing in a tunnel.

[0031] Figure 12 It is a schematic diagram of the water flow direction in a blocking state of a blocking device for sudden mud and water gushing in a tunnel according to the present invention.

[0032] As shown in the figure: 01, excavation section; 02, construction section; 03, drainage trough; 1, double blocking mechanism; 2, base; 3, blocking plate; 4, buoy; 5, hood; 6, floater; 7, stand; 8, blocking door; 21, drainage chamber; 22, inclined platform; 221, drainage trough; 23, support platform; 24, bearing platform; 25, rotating shaft; 26, stand; 27, protective plate; 28, drainage channel; 31, Bushing; 32. Flat plate; 33. Counterweight; 34. Straight rod; 35. Water pressure detector; 36. Start switch; 361. Transparent cover; 362. Enclosed cavity; 363. Sliding rod; 364. Fixed platform; 365. Slip ring; 37. Airbag; 51. Hollow rod; 61. Top plate; 62. Buoyancy plate; 71. Rib plate; 81. Placement groove; 82. Impact plate; 83. Storage groove; 84. Connecting cover. DETAILED DESCRIPTION

[0033] The present invention will be described in further detail below with reference to the accompanying drawings.

[0034] Combined with attachment Figure 1 , Attachment Figure 2 and attached Figure 3 As shown, a blocking device for sudden mud and water gushing in a tunnel comprises a double blocking mechanism 1, which is arranged between the excavation section 01 and the construction section 02. The double blocking mechanism 1 comprises a base 2, on which a freely rotating blocking plate 3 is provided. Vertical frames 7 are provided on both sides of the top of the base 2, and the vertical frames 7 are in contact with the side walls of the tunnel. A blocking door 8 is hingedly provided on the inner side of the vertical frames 7. The blocking plate 3 and the blocking door 8 constitute a double blocking defense line. A float 4 and a hood 5 are also provided in the base 2. The float 4 is connected to the blocking plate 3 by a steel rope, and the float 4 relies on buoyancy to pull the blocking plate 3 to rotate. The hood 5 is connected to the blocking door 8 by a steel rope. Driven by the impact of the water flow, the hood 5 pulls the blocking door 8 to close automatically. A drainage system is provided in the base 2.

[0035] Combined with attachment Figure 5 , Attachment Figure 7 and attached Figure 8As shown, the blocking plate 3 includes a sleeve 31, a flat plate 32 and a plurality of counterweights 33 are respectively provided on both sides of the sleeve 31, a rotating shaft 25 is provided inside the base 2 for rotating with the sleeve 31, a plurality of straight rods 34 are provided on the front side of the flat plate 32, and gaps are left between adjacent straight rods 34. The center of gravity of the blocking plate 3 is close to the rotating shaft 25 and biased toward the flat plate 32.

[0036] Working principle of the blocking plate 3: The blocking plate 3 is freely rotated by the rotational cooperation of the shaft sleeve 31 and the rotating shaft 25. The center of gravity of the blocking plate 3 is adjusted to a position close to the rotating shaft 25 and biased towards the flat plate 32 through multiple counterweights 33, so that the blocking plate 3 is placed horizontally in the base 2 in the normal state. When the working vehicle passes through the blocking plate 3, the protective plate 27 prevents the wheel from hitting the counterweight 33, so that the blocking plate 3 stands up. The gap between the straight rods 34 facilitates the accumulation of water on the road to flow into the drainage chamber 21.

[0037] Combined with attachment Figure 1 , Attachment Figure 5 , Attachment Figure 7 , Attachment Figure 10 and attached Figure 12 As shown, the drainage system includes a drainage chamber 21 inside the base 2, the drainage chamber 21 is located below the straight rod 34, and drainage channels 28 are provided on both sides of the drainage chamber 21. The drainage channel 28 is connected to the drainage trough 03 at the construction section 02, and the float 4 is placed in the drainage chamber 21. The hood 5 is received in the groove at the bottom of the drainage chamber 21. The drainage system also includes a drainage trough 221 on the inclined platform 22, and the drainage trough 221 connects the drainage chamber 21 and the bottom cavity of the protective plate 27. When the blocking plate 3 is erected, there is a gap between the blocking plate 3 and the protective plate 27.

[0038] Working principle of the drainage system: In the initial stage of water gushing, water flows into the drainage cavity 21 through the gap of the straight rod 34, and then flows into the drainage groove 03 through the drainage channel 28 for discharge. After the water flow accelerates, when the water cannot be completely discharged through the drainage groove 03, the base 2 is already filled with water, and the float 4 and the floater 6 float up due to the buoyancy, and lifts the blocking plate 3. The float 4 is subjected to the impact of the water and pulls the blocking plate 3 to a vertical state to block the water flow. After part of the water flows through the drainage groove 221, it is discharged through the gap between the blocking plate 3 and the protective plate 27. At this time, the impact force of the discharged water flow is reduced. After the water flow bursts out, the blocking door 8 is closed, and the water flows through the drainage cavity 21 and flows through the space between the blocking door 8 and the blocking plate 3 to be discharged, reducing the impact force of the water.

[0039] Combined with attachment Figure 4 , Attachment Figure 6 , Attachment Figure 7 and attached Figure 8As shown, the front side of the drainage chamber 21 is provided with a supporting platform 24 that cooperates with the straight rod 34, the rear side of the drainage chamber 21 is provided with an inclined platform 22, and the inclined platform 22 is provided with a support platform 23 that cooperates with the flat plate 32. A plurality of vertical plates 26 are provided behind the inclined platform 22, and the counterweight block 33 is located in the gap between the vertical plates 26. A protective plate 27 is provided on the top of the vertical plate 26, and the protective plate 27 is located above the counterweight block 33. The counterweight block 33 is limited and cooperates with the rear side of the inclined platform 22. A floater 6 is provided in the internal groove of the support platform 23. The floater 6 includes a buoyancy plate 62, and a top plate 61 is provided on the top of the buoyancy plate 62. The top plate 61 passes through the through hole at the top of the support platform 23 and cooperates with the flat plate 32, and the top plate 61 is limited and cooperates with the blocking door 8.

[0040] Working principle of the base 2 and the blocking plate 3: the supporting platform 24 and the supporting platform 23 both support the blocking plate 3, and the vertical plate 26 supports the protective plate 27, so that the vehicle can pass over the blocking plate 3 and the protective plate 27. When water gushes, the buoyancy is used to make the floater 6 and the pontoon 4 float up, and the top plate 61 of the floater 6 and the pontoon 4 apply an upward thrust to the blocking plate 3, so that the blocking plate 3 stands up. After the top plate 61 extends out of the through hole at the top of the support platform 23, the buoyancy plate 62 is limited by the support platform 23, so that the top plate 61 maintains its position. When the blocking door 8 is closed, the blocking door 8 is limited by the vertical frame 7 on the one hand and by the top plate 61 on the other hand, which jointly provide support force for the blocking door 8 to prevent the blocking door 8 from opening due to water pressure.

[0041] Combined with attachment Figure 4 , Attachment Figure 7 and attached Figure 9 As shown, airbags 37 are provided in the grooves on both sides of the plurality of straight rods 34. When the airbags 37 are inflated, adjacent airbags 37 are squeezed, and the airbags 37 on the side are in contact with the stand 7. A water pressure detector 35 is provided on the flat plate 32, and one of the counterweights 33 is replaced by a start switch 36. The start switch 36 provides a start signal for the inflation of the airbags 37. The start switch 36 includes a transparent cover 361. The interior of the transparent cover 361 is a closed cavity 362. A slide rod 363 is obliquely provided in the closed cavity 362. When the blocking plate 3 is in a horizontal state, the end of the slide rod 363 close to the sleeve 31 is lower than the end away from the sleeve 31. A slip ring 365 is provided for sliding on the end of the slide rod 363 close to the sleeve 31. A fixed platform 364 is provided on the end of the slide rod 363 away from the sleeve 31. Both the slip ring 365 and the fixed platform 364 are provided with matching contacts.

[0042] The working principle of the starting switch 36 and the airbag 37 is as follows: when the blocking plate 3 is placed horizontally, due to the inclined setting of the slide rod 363, the slip ring 365 cannot automatically slide to the fixed platform 364 due to its own gravity, and the two contacts cannot contact each other. After the blocking plate 3 is erected, the angle of the slide rod 363 changes, and the slip ring 365 automatically slides to the fixed platform 364. The two contacts contact, which triggers the internal circuit of the blocking plate 3, and then the airbag 37 starts to inflate, blocking the gaps between the straight rods 34, and at the same time blocking the gaps between the edge straight rods 34 and the rib plates 71, thereby increasing the blocking space of the blocking plate 3. The water pressure detector 35 detects the water pressure in real time to provide data reference for the alarm in the tunnel. The inflation of the airbag 37 can be done by using a gas cylinder hidden at the bottom or inside of the blocking plate 3, or by using chemical reaction gas. The inflation device needs to add a delay device to allow the blocking plate 3 to be inflated after it is fully erected.

[0043] Combined with attachment Figure 2 and attached Figure 11 As shown, the blocking door 8 is provided with a placement groove 81 on the rear side, and an impact plate 82 is hingedly provided in the placement groove 81. A storage groove 83 is provided on the inner side of the impact plate 82. The inner boss of the storage groove 83 is connected to the placement groove 81 by a steel rope. The top and bottom of the inner side of the impact plate 82 are provided with a connecting cover 84, and the connecting cover 84 is connected to the placement groove 81. The rear side of the stand 7 is provided with a rib plate 71 connected to the base 2. The upper and lower ends of the hood 5 are provided with hollow rods 51. The two hollow rods 51 are connected to the outer sides of the two impact plates 82 by steel ropes, and the lower hollow rod 51 is connected to the base 2 by an elastic rope.

[0044] The working principle of the hood 5 and the blocking door 8: when water gushes, the blocking plate 3 stands up, and the hood 5 floats due to the buoyancy of the hollow rod 51. When the water level is higher than the top of the blocking plate 3, the hood 5 rushes to the top of the blocking plate 3. After the water flow bursts out, the water flow hits the hood 5. Since the hollow rod 51 below is pulled by the elastic rope, the hollow rod 51 above is away from the hollow rod 51 below due to buoyancy, thereby causing the hood 5 to open, increasing the force-bearing surface of the hood 5. The huge impact force causes the hood 5 to open the impact plate 82 from the placement groove 81 through the steel rope. After the impact plate 82 is opened, the impact plate 82 is impacted by the water flow, causing the impact plate 82 to pull the blocking door 8 through the steel rope. After the blocking door 8 rotates to a certain angle, the blocking door 8 is affected by the impact force of the water and then automatically closes.

[0045] In the specific implementation of the present invention, the double blocking mechanism 1 is installed between the excavation section 01 and the construction section 02. It is moved along with the progress of the tunnel construction, or the position of the water accumulation section is determined by measuring, and the double blocking mechanism 1 is placed at a suitable position in the excavation section 01. In the normal state, the blocking door 8 is opened and the blocking plate 3 is placed flat, as shown in the attached figure. Figure 3In the state shown, vehicles are allowed to pass without affecting normal construction operations. The seepage water in the excavation section 01 can be discharged through the drainage chamber 21. When a sudden mud and water gushing occurs, when the water flow in the initial stage is not large, workers can evacuate urgently. The gushing water is discharged through the drainage chamber 21 and discharged through the drainage trough 03. When the water flow intensifies, the buoyancy of the buoy 4 and the float 6 will lift the blocking plate 3, so that the blocking plate 3 stands up. The blocking plate 3 blocks the impact of water, thereby buying time for evacuation. After the water flow bursts out, the blocking door 8 is closed through the hood 5 and the impact plate 82, as shown in the attached figure. Figure 2 and attached Figure 4 In the state shown, strive for evacuation opportunity, reduce the water pressure on the blocking plate 3 and the blocking door 8 through the drainage system to prevent them from being damaged. The drainage system reduces the impact force of the water flow by changing the drainage direction to prevent harm to the evacuated personnel.

[0046] The above description of the present invention and its embodiments is non-limiting. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if a person skilled in the art is inspired by the above and, without departing from the purpose of the present invention, designs structures and embodiments similar to the technical solution without creatively designing, they shall fall within the scope of protection of the present invention.

Claims

1. A device for preventing mud and water inrush in a tunnel, comprising a double blocking mechanism, the double blocking mechanism being arranged between the excavation section and the construction section, characterized in that: The double blocking mechanism includes a base, on which a freely rotating blocking plate is provided, and vertical frames are provided on both sides of the top of the base. The vertical frames are attached to the side walls of the tunnel, and blocking doors are hingedly provided on the inner sides of the vertical frames. The blocking plate and the blocking door form a double blocking defense line; The base is also equipped with a float and a hood. The float is connected to the blocking plate by a steel rope. The float relies on buoyancy to pull the blocking plate to rotate. The hood is connected to the blocking door by a steel rope. Driven by the impact of water flow, the hood pulls the blocking door to automatically close. A drainage system is provided in the base. The blocking plate includes a shaft sleeve, a flat plate and a plurality of counterweights are provided on both sides of the shaft sleeve, a rotating shaft is provided inside the base for rotating with the shaft sleeve, and a plurality of straight rods are provided on the front side of the flat plate, with gaps left between adjacent straight rods; The drainage system includes a drainage cavity inside the base, the drainage cavity is located below the straight rod, and drainage channels are provided on both sides of the drainage cavity. The drainage channels are connected to the drainage trough at the construction section. The float is placed in the drainage cavity, and the hood is stored in the groove at the bottom of the drainage cavity. The front side of the drainage chamber is provided with a supporting platform that cooperates with the straight rod, the rear side of the drainage chamber is provided with an inclined platform, the inclined platform is provided with a supporting platform that cooperates with the flat plate, and a plurality of vertical plates are provided behind the inclined platform. The counterweight block is located in the gap between the vertical plates, and a protective plate is provided on the top of the vertical plate. The protective plate is located above the counterweight block. The counterweight block is limited and cooperates with the rear side of the inclined platform. A floater is provided in the internal groove of the support platform. The floater includes a buoyancy plate. A top plate is provided on the top of the buoyancy plate. The top plate passes through the through hole on the top of the support platform and cooperates with the flat plate. When the blocking door is closed, the top plate limits the blocking door. The drainage system also includes a drainage trough on the inclined platform, the drainage trough communicating with the drainage cavity and the cavity at the bottom of the protective plate, and when the blocking plate is erected, a gap exists between the blocking plate and the protective plate; The rear side of the blocking door is provided with a placement slot, an impact plate is hingedly provided in the placement slot, a storage slot is provided inside the impact plate, a boss inside the storage slot is connected to the placement slot by a steel rope, a connection cover is provided at the top and bottom of the inner side of the impact plate, the connection cover is connected to the placement slot, and a rib plate connected to the base is provided on the rear side of the stand; The upper and lower ends of the hood are both provided with hollow rods, the two hollow rods are connected to the outer sides of the two impact plates through steel ropes, and the lower hollow rod is connected to the base through an elastic rope.

2. The device for preventing sudden mud and water inrush in a tunnel according to claim 1, characterized in that: Air bags are provided in the grooves on both sides of the plurality of straight rods. When the air bags are inflated, the adjacent air bags are squeezed and the air bags on the sides are in contact with the stand.

3. The device for preventing sudden mud and water inrush in a tunnel according to claim 2, characterized in that: The flat plate is provided with a water pressure detector, in which one of the counterweights is replaced by a start switch, which provides a start signal for airbag inflation. The start switch includes a transparent cover, a closed cavity inside the transparent cover, and a sliding rod obliquely provided in the closed cavity. When the blocking plate is in a horizontal state, the end of the sliding rod close to the shaft sleeve is lower than the end away from the shaft sleeve. A slip ring is provided for sliding on the end of the sliding rod close to the shaft sleeve, and a fixed platform is provided on the end of the sliding rod away from the shaft sleeve. Both the slip ring and the fixed platform are provided with matching contacts.

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