A dual-output shaft underwater motor with a single cable for well use

Abstract

The present application relates to a double-outlet shaft underwater motor with a single cable lead-out for a well, and relates to the technical field of submersible motors, which includes a housing, a stator is fixedly connected in the housing, a rotor is rotatably connected in the stator, the stator and the rotor are coaxially arranged, a transmission shaft is passed through and fixedly connected in the rotor, both ends of the transmission shaft pass through the housing and are placed outside the housing, an upper guide bearing seat and a lower guide bearing seat are respectively fixedly connected at both ends of the housing, a rolling bearing is installed between the upper guide bearing seat and the transmission shaft, an axial bearing bearing is installed between the lower guide bearing seat and the transmission shaft, a lead-out cable is passed through and fixedly connected on the upper guide bearing seat, and the lead-out cable is connected to the stator. The present application has the effect of satisfying the requirement that a single motor can complete two drives at the same time.

Description

Technical Field

[0001] The present application relates to the technical field of submersible motors, and in particular to a double-axle underwater motor led out by a single cable for use in wells. Background Art

[0002] Submersible motors are motors designed for underwater environments. They are waterproof and pressure-resistant and can run stably underwater for a long time. Submersible motors are widely used in submersible pumps, underwater thrusters, underwater robots, underwater photography equipment and other fields.

[0003] Submersible motors are usually used with submersible pumps to lift groundwater and other liquids. This type of product is usually a single-shaft type with only one external drive end, and can only complete a single load drive. However, in many real-world application scenarios, there is a widespread need to complete two drive functions simultaneously in a single well.

[0004] The related technology usually requires placing two motors in the well and leading out at least two power cables. This not only increases the cost but also faces cumbersome installation and maintenance problems such as multiple cable entanglements, large space occupation, and multiple control devices when arranged underwater. Summary of the invention

[0005] In order to meet the actual demand of a single motor completing two drives at the same time, the present application provides a double-output shaft underwater motor led out by a single cable for wells.

[0006] The present application provides a single-cable dual-shaft underwater motor for wells using the following technical solution:

[0007] A double-output shaft underwater motor with single-cable lead-out for wells comprises a shell, a stator is fixedly connected in the shell, a rotor is rotatably connected in the stator, the stator and the rotor are coaxially arranged, a transmission shaft is passed through and fixedly connected in the rotor, both ends of the transmission shaft pass through the shell and are placed outside the shell, an upper guide bearing seat and a lower guide bearing seat are respectively fixedly connected at both ends of the shell, a rolling bearing is installed between the upper guide bearing seat and the transmission shaft, an axial load-bearing bearing is installed between the lower guide bearing seat and the transmission shaft, a lead-out cable is passed through and fixedly connected to the upper guide bearing seat, and the lead-out cable is connected to the stator.

[0008] By adopting the above technical solution, electricity can be supplied to the stator through a lead cable to rotate the rotor, thereby driving the transmission shaft to rotate, thereby driving two different loads at the same time through the two ends of the transmission shaft.

[0009] Specifically, if submersible pumps are equipped at both ends, submersible pumps with the same or different directions can generate water flows in the same or different directions, thereby achieving liquid lifting effects in a variety of directional combinations; one end can also be equipped with a pump and the other end with a reamer, gearbox or other loads, so that different drive functions can be realized at both ends to meet the requirements of multiple working scenarios.

[0010] Therefore, a dual-shaft motor is used to replace the original two submersible motors, which not only meets the actual needs of a single motor to complete two driving energies at the same time, but also only requires one cable as a lead-out line. Compared with two motors with dual cables, it brings great convenience in installation, reduces the problems of multiple cable entanglement, large space occupation, and multiple control devices, and obtains the advantages of simple structure, small size, and easy installation.

[0011] Optionally, both ends of the transmission shaft are provided with dynamic seals for sealing the connection between the transmission shaft and the housing.

[0012] By adopting the above technical solution, the connection between the transmission shaft and the housing can be sealed by a dynamic seal, thereby reducing the occurrence of water flowing directly into the lower guide bearing seat and the upper guide bearing seat through the connection between the two.

[0013] Optionally, both the upper guide bearing seat and the lower guide bearing seat are provided with oil filling holes, the oil filling hole on the upper guide bearing seat is connected to the rolling bearing, and the oil filling hole on the lower guide bearing seat is connected to the axial load-bearing bearing, and the oil filling hole is threadedly sealed with a sealing bolt for sealing the oil filling hole.

[0014] By adopting the above technical solution, lubricating oil can be injected into the upper guide bearing seat and the lower guide bearing through the oil filling hole, thereby reducing the friction between the rolling bearing and the axial load-bearing bearing and the transmission shaft.

[0015] Optionally, an air pressure balance hole is provided on the upper guide bearing seat and the lower guide bearing seat, one end of the air pressure balance hole is connected to the interior of the upper guide bearing seat or the lower guide bearing seat, and a pressure balance valve is installed at the air pressure balance hole.

[0016] By adopting the above technical solution, the air pressure in the upper guide bearing seat and the lower guide bearing can be balanced through the air pressure balance hole and the pressure balance valve, so that they can maintain a better working state.

[0017] Optionally, the transmission shaft includes a coaxially arranged upper shaft, a lower shaft and a sliding bearing, the sliding bearing is placed between the upper shaft and the lower shaft, the outer ring of the sliding bearing is fixedly connected to the stator, and the inner ring of the sliding bearing is fixedly connected to the upper shaft and the lower shaft.

[0018] By adopting the above technical solution, the upper shaft and the lower shaft can be straightened through the sliding bearing between the upper shaft and the lower shaft, thereby improving the stability of the rotor and the transmission shaft.

[0019] Optionally, an upper coupling and a lower coupling are respectively fixedly connected to both ends of the transmission shaft.

[0020] By adopting the above technical solution, the two ends of the transmission shaft can be connected to different loads through the upper coupling and the lower coupling, thereby driving the load to rotate.

[0021] Optionally, a connecting shaft is provided at the lower end of the transmission shaft, the connecting shaft is coaxially arranged with the transmission shaft, and a plurality of limit blocks are fixedly connected to the outer arc surface of the connecting shaft, and the plurality of limit blocks are equidistantly arranged around the axis of the connecting shaft, a slot is provided at the lower end of the transmission shaft, the connecting shaft is inserted into the slot, a plurality of limit grooves are provided on the inner wall of the slot, the limit grooves correspond to the slots one by one and the limit blocks are clamped in the limit grooves, a bearing plate for reducing the axial force of the transmission shaft is fixedly connected to the connecting shaft, an abutment block is slidably connected to the bearing plate, and through holes are provided on the connecting shaft and the transmission shaft opposite to the abutment block, the through hole is connected to the lower guide bearing seat, the sliding path of the abutment block on the bearing plate coincides with the diameter of the bearing plate, and a control component for controlling the abutment block to slide on the bearing plate is provided between the connecting shaft and the slot.

[0022] By adopting the above technical solution, a slot can be opened on the transmission shaft, so that the connecting shaft can be restricted on the transmission shaft by sliding and plugging, and then when the transmission shaft rotates, the connecting shaft can rotate with the transmission shaft, and then the power of this motor is output outward through the connecting shaft. At the same time, when the connecting shaft enters the slot, the abutment block on the bearing plate can be slid to the side away from the axis of the bearing plate through the control component, and abut with the lower end of the axial bearing bearing, thereby not only supporting the lower end of the axial bearing bearing but also limiting the axial sliding of the connecting shaft in the slot of the transmission shaft, so that the connecting shaft is fixed in the slot, and the pressure of the axial bearing bearing on the lower guide bearing seat can be reduced, and then the connecting shaft can share part of the pressure for the lower guide bearing seat, thereby increasing the service life of the axial bearing bearing.

[0023] Optionally, the control component includes a toggle rod fixedly connected to the bottom of the slot, and one end of the toggle rod away from the bottom of the slot extends toward the axis of the connecting shaft. A sliding hole is provided on the supporting plate, and the sliding hole corresponds to the abutment block one-to-one, and the direction in which the sliding hole is opened coincides with the diameter of the supporting plate. The toggle rod corresponds to the abutment block one-to-one, and when the connecting shaft enters the slot, a section of the toggle rod away from the bottom of the slot abuts against the abutment block, and drives the abutment block to move to the side away from the axis of the supporting plate, and finally makes the abutment block abut against the lower end of the axial load-bearing bearing.

[0024] By adopting the above-mentioned technical solution, when the connecting shaft enters the slot, a section of the multiple toggle rods away from the bottom of the slot will remain in contact with the side wall of the abutment block, and drive the abutment block to move to the side away from the axis of the supporting plate, thereby causing the abutment block to enter the lower end of the axial load-bearing bearing and abut against the lower end of the axial load-bearing bearing, thereby causing the abutment block to be automatically placed at the lower end of the axial load-bearing bearing during the process of the connecting shaft entering the slot.

[0025] In summary, the present application includes at least one of the following beneficial technical effects:

[0026] 1. Both ends of the submersible pump can be equipped with the same or different directions of the submersible pumps, which can generate water flow in the same or different directions, and achieve liquid lifting effects in various directions. One end can also be equipped with a pump and the other end with a reamer, gearbox and other loads, and the two ends can achieve different drive functions to meet the needs of multiple working conditions.

[0027] 2. Use a double-shaft motor to replace the original two submersible motors, which not only meets the actual needs of a single motor to complete two driving energies at the same time, but also only requires one cable as a lead-out line. Compared with two motors with double cables, it brings great convenience in installation, reduces the problems of multiple cable entanglement, large space occupation, and multiple control devices, and obtains the advantages of simple structure, small size, and easy installation;

[0028] 3. The upper shaft and the lower shaft can be straightened through the sliding bearing between the upper shaft and the lower shaft to improve the stability of the rotor and the transmission shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of Example 1 of the present application;

[0030] Figure 2 yes Figure 1 A schematic diagram of the enlarged structure of part A;

[0031] Figure 3 yes Figure 1 A schematic diagram of the enlarged structure of part B;

[0032] Figure 4 is a schematic diagram of the structure of the cable of Example 1 of the present application;

[0033] Figure 5 is a schematic structural diagram of a toggle lever according to Embodiment 2 of the present application;

[0034] Figure 6 It is a schematic diagram of the structure of the sliding hole of Example 2 of the present application.

[0035] In the figure, 1, housing; 2, rotor; 3, stator; 4, transmission shaft; 41, upper shaft; 42, lower shaft; 43, sliding bearing; 44, slot; 441, limit groove; 45, through hole; 5, upper guide bearing seat; 6, lower guide bearing seat; 7, rolling bearing; 8, axial load-bearing bearing; 9, lead-out cable; 10, dynamic seal; 11, oil filling hole; 12, sealing bolt; 13, air pressure balance hole; 14, pressure balance valve; 15, upper coupling; 16, lower coupling; 17, connecting shaft; 171, limit block; 18, bearing plate; 181, sliding hole; 19, abutment block; 20, water-swelling block; 21, control component; 211, toggle lever. DETAILED DESCRIPTION

[0036] The following is combined with Figure 1 -Attached Figure 6 , further details of this application are given.

[0037] Example 1, a double-axle underwater motor led out of a single cable for a well, referring to Figure 1 , comprising a shell 1, the shell 1 is arranged in a tubular shape, a stator 3 with a winding coil is fixedly connected in the shell 1, a rotor 2 with a permanent magnet is rotatably connected in the stator 3, and the stator 3 is coaxially arranged with the rotor 2. A transmission shaft 4 is passed through and fixedly connected in the rotor 2, and both ends of the transmission shaft 4 pass through the shell 1 and are placed outside the shell 1.

[0038] The transmission shaft 4 includes an upper shaft 41, a lower shaft 42 and a sliding bearing 43. The sliding bearing 43 is placed between the upper shaft 41 and the lower shaft 42. The outer ring of the sliding bearing 43 is fixedly connected to the stator 3, and the inner ring of the sliding bearing 43 is fixedly connected to the upper shaft 41 and the lower shaft 42. The sliding bearing 43 can straighten the upper shaft 41 and the lower shaft 42, so that the upper shaft 41 and the lower shaft 42 remain stable during rotation, thereby keeping the transmission shaft 4 stable as a whole.

[0039] Reference Figure 1 , Figure 2 and Figure 3 An upper coupling 15 for connecting a load is fixedly connected to one end of the upper shaft 41 away from the sliding bearing 43 , and a lower coupling 16 for connecting a load is fixedly connected to one end of the lower shaft 42 away from the sliding bearing 43 .

[0040] An upper guide bearing seat 5 and a lower guide bearing seat 6 are fixedly connected to both ends of the housing 1, and a rolling bearing 7 is installed between the upper guide bearing seat 5 and the transmission shaft 4. The rolling bearing 7 can be set as a deep groove bearing or an angular contact bearing, and two of them can be stacked in the axial direction of the transmission shaft 4. An axial load-bearing bearing 8 is installed between the lower guide bearing seat 6 and the transmission shaft 4. The axial load-bearing bearing 8 can be set as two angular contact ball bearings, which are installed back to back or face to face, and can bear both axial force and radial force.

[0041] Reference Figure 1 , Figure 2 and Figure 4 , a lead cable 9 is passed through and fixedly connected to the upper guide bearing seat 5, and the lead cable 9 is connected to the stator 3. Thus, the stator 3 can be energized through a lead cable 9 to rotate the rotor 2, thereby driving the transmission shaft 4 to rotate, thereby driving two different loads at the same time through the two ends of the transmission shaft 4.

[0042] Reference Figure 1 , Figure 3 and Figure 4 At the same time, in order to reduce the occurrence of water flowing directly into the lower guide bearing seat 6 and the upper guide bearing seat 5 through the connection between the two, both ends of the transmission shaft 4 are provided with dynamic seals 10 for sealing the connection between the transmission shaft 4 and the housing 1. The dynamic seal 10 in this embodiment is set as a double-end mechanical seal or a multi-pass oil seal.

[0043] Both the upper guide bearing seat 5 and the lower guide bearing seat 6 are provided with oil filling holes 11. The oil filling hole 11 on the upper guide bearing seat 5 is connected to the rolling bearing 7, and the oil filling hole 11 on the lower guide bearing seat 6 is connected to the axial load-bearing bearing 8. The oil filling hole 11 is threadedly sealed with a sealing bolt 12 for sealing the oil filling hole 11.

[0044] Before placing the motor underwater, the sealing bolt 10 can be rotated, and then the sealing bolt 12 can be taken out from the oil filling hole 11, and then lubricating oil can be injected into the rolling bearing 7 or the axial load bearing bearing 8 through the oil filling hole 11. The friction between the rolling bearing 7 and the axial load bearing bearing 8 and the transmission shaft 4 can be reduced.

[0045] In order to timely balance the air pressure in the upper guide bearing seat 5 and the lower guide bearing seat 6, an air pressure balance hole 13 is opened on the upper guide bearing seat 5 and the lower guide bearing seat 6, one end of the air pressure balance hole 13 is connected to the interior of the upper guide bearing seat 5 or the lower guide bearing seat 6, and a pressure balance valve 14 is installed at the air pressure balance hole 13.

[0046] Embodiment 2 is different from Embodiment 1 in that: Figure 5 and Figure 6The lower end of the transmission shaft 4 is provided with a connecting shaft 17, which is located at the lower end of the lower shaft 42, and the connecting shaft 17 is coaxially arranged with the transmission shaft 4. A plurality of limit blocks 171 are fixedly connected to the outer arc surface of the connecting shaft 17, and the limit blocks 171 are arranged along the length direction of the connecting shaft 17 and the plurality of limit blocks 171 are arranged equidistantly around the axis of the connecting shaft 17. A slot 44 is provided at the lower end of the transmission shaft 4, and the slot 44 is arranged as a circular groove and the length direction of the slot 44 is parallel to the length direction of the transmission shaft 4. The connecting shaft 17 is slidably inserted into the slot 44.

[0047] A plurality of limiting grooves 441 are provided on the inner wall of the slot 44, and the limiting grooves 441 are arranged along the length direction of the slot 44 and the limiting grooves 441 correspond to the slots 44 one by one. The limiting blocks 171 are engaged in the limiting grooves 441. Therefore, when the transmission shaft 4 rotates, due to the engaging effect of the limiting grooves 441 and the limiting blocks 171, the connecting shaft 17 can rotate together with the transmission shaft 4.

[0048] A hole is provided at one end of the connecting shaft 17 near the bottom of the slot 44. A bearing plate 18 for reducing the axial force of the transmission shaft 4 is fixedly connected in the hole of the connecting shaft 17. Four abutment blocks 19 are slidably connected to the bearing plate 18. The four abutment blocks 19 are all placed on the side of the bearing plate 18 close to the axial bearing bearing 8 and the four abutment blocks 19 are equidistantly arranged around the axis of the bearing plate 18. Through holes 45 are provided on the side walls of the connecting shaft 17 and the side walls of the transmission shaft 4 facing the abutment blocks 19. The through holes 45 are connected to the lower guide bearing seat 6. The sliding path of the abutment blocks 19 on the bearing plate 18 coincides with the diameter of the bearing plate 18.

[0049] A control assembly 21 for controlling the sliding of the abutment block 19 on the carrier plate 18 is provided between the connecting shaft 17 and the slot 44. The control assembly 21 includes four toggle rods 211, one end of which is fixedly connected to the bottom of the slot 44, and one end of the toggle rod 211 away from the bottom of the slot 44 extends toward one side of the axis of the connecting shaft 17, and the plurality of toggle rods 211 are staggered, and the toggle rods 211 correspond to the abutment blocks 19 one by one.

[0050] The carrier plate 18 is provided with sliding holes 181 , which correspond to the abutment blocks 19 one by one. The directions of the sliding holes 181 coincide with the diameter of the carrier plate 18 , and the four sliding holes 181 are interconnected.

[0051] Then, when the connecting shaft 17 enters the slot 44, the section of the toggle rod 211 away from the bottom of the slot 44 will abut against the abutment block 19, and drive the abutment block 19 to move to the side away from the axis of the bearing plate 18, and finally make the abutment block 19 abut against the lower end of the axial bearing bearing 8. At the same time, in order to improve the airtightness between the abutment block 19 and the axial bearing bearing 8, a water-expandable block 20 is fixedly connected to the side of the abutment block 19 close to the axial bearing bearing 8, and the water-expandable block 20 is embedded in the abutment block 19, so that when the liquid contacts the water-expandable block 20, the water-expandable block 20 will expand to a certain extent. Then, the gap between the abutment block 19 and the axial bearing bearing 8 is reduced.

[0052] The implementation principle of Example 2 is: the connecting shaft 17 is restricted on the transmission shaft 4 by sliding and plugging, and then when the transmission shaft 4 rotates, the connecting shaft 17 can rotate together with the transmission shaft 4 under the restriction of the limit groove 441 and the limit block 171, and then the power of this motor is output to the outside through the connecting shaft 17.

[0053] At the same time, when the connecting shaft 17 enters the slot 44, a section of the multiple toggle rods 211 away from the bottom of the slot 44 will remain in contact with the side wall of the abutment block 19, and drive the abutment block 19 to move to the side away from the axis of the carrier plate 18, and finally abut the lower end of the inner ring of the axial bearing 8, and then the abutment block 19 is automatically placed at the lower end of the axial bearing bearing 8 during the process of the connecting shaft 17 entering the slot 44. In this way, the lower end of the axial bearing bearing 8 is supported and the axial sliding of the connecting shaft 17 in the slot 44 of the transmission shaft 4 can be restricted, so that the connecting shaft 17 is fixed in the slot 44, and the connecting shaft 17 shares part of the pressure for the lower guide bearing seat 6, which can reduce the pressure of the axial bearing bearing 8 on the lower guide bearing seat 6.

[0054] The embodiments of this specific implementation are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. The same components are represented by the same figure marks. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A double-axle underwater motor for a well with a single cable lead-out, comprising a housing (1), a stator (3) fixedly connected to the housing (1), a rotor (2) rotatably connected to the stator (3), the rotor (2) and the stator (3) being coaxially arranged, characterized in that: A transmission shaft (4) is passed through and fixedly connected to the rotor (2); both ends of the transmission shaft (4) pass through the housing (1) and are placed outside the housing (1); an upper guide bearing seat (5) and a lower guide bearing seat (6) are respectively fixedly connected to the two ends of the housing (1); a rolling bearing (7) is installed between the upper guide bearing seat (5) and the transmission shaft (4); an axial bearing bearing (8) is installed between the lower guide bearing seat (6) and the transmission shaft (4); a lead-out cable (9) is passed through and fixedly connected to the upper guide bearing seat (5); the lead-out cable (9) is connected to the stator (3); both the upper guide bearing seat (5) and the lower guide bearing seat (6) are provided with oil filling holes (11); The oil filling hole (11) is connected to the rolling bearing (7), the oil filling hole (11) on the lower guide bearing seat (6) is connected to the axial load-bearing bearing (8), a sealing bolt (12) for sealing the oil filling hole (11) is threadedly sealed and connected to the oil filling hole (11), a connecting shaft (17) is provided at the lower end of the transmission shaft (4), the connecting shaft (17) is coaxially arranged with the transmission shaft (4), a plurality of limit blocks (171) are fixedly connected to the outer arc surface of the connecting shaft (17), the plurality of limit blocks (171) are equidistantly arranged around the axis of the connecting shaft (17), a slot (44) is provided at the lower end of the transmission shaft (4), the connecting shaft (17) is inserted into the slot (44), A plurality of limiting grooves (441) are provided on the inner wall of the slot (44), the limiting grooves (441) correspond to the slot (44) one by one and the limiting blocks (171) are snapped into the limiting grooves (441), a bearing plate (18) for reducing the axial force of the transmission shaft is fixedly connected in the connecting shaft (17), an abutment block (19) is slidably connected to the bearing plate (18), through holes (45) are provided on the connecting shaft (17) and the transmission shaft (4) facing the abutment block (19), the through holes (45) are connected to the lower guide bearing seat (6), a sliding path of the abutment block (19) on the bearing plate (18) coincides with the diameter of the bearing plate (18), the connecting shaft (17) and the transmission shaft (4) are slidably connected to the bearing plate (18), a through hole (45) is provided on the connecting shaft (17) and the transmission shaft (4) facing the abutment block (19), the through hole (45) is connected to the lower guide bearing seat (6), a sliding path of the abutment block (19) on the bearing plate (18) coincides with the diameter of the bearing plate (18), and the connecting shaft (17) and the transmission shaft (4) are slidably connected to the bearing plate (18). A control assembly (21) for controlling the abutment block (19) to slide on the carrier plate (18) is provided between the slots (44), the control assembly (21) comprising a toggle rod (211) fixedly connected to the bottom of the slot (44), one end of the toggle rod (211) away from the bottom of the slot (44) extending toward one side of the axis of the connecting shaft (17), a sliding hole (181) is provided on the carrier plate (18), the sliding hole (181) corresponds one-to-one with the abutment block (19), and the direction in which the sliding hole (181) is provided coincides with the diameter of the carrier plate (18), the toggle rod (211) corresponds one-to-one with the abutment block (19), and when the connecting shaft (17) enters the slot (44),A section of the toggle rod (211) away from the bottom of the slot (44) abuts against the abutment block (19), drives the abutment block (19) to move to a side away from the axis of the bearing plate (18), and finally causes the abutment block (19) to abut against the lower end of the axial load-bearing bearing (8).

2. A double-axle underwater motor with single cable lead-out for wells according to claim 1, characterized in that: Both ends of the transmission shaft (4) are provided with dynamic seals (10) for sealing the connection between the transmission shaft (4) and the housing (1).

3. A double-axle underwater motor with single cable lead-out for wells according to claim 1, characterized in that: The upper guide bearing seat (5) and the lower guide bearing seat (6) are both provided with an air pressure balance hole (13), one end of the air pressure balance hole (13) is connected to the interior of the upper guide bearing seat (5) or the lower guide bearing seat (6), and a pressure balance valve (14) is installed at the air pressure balance hole (13).

4. A double-axle underwater motor with single cable lead-out for wells according to claim 1, characterized in that: The transmission shaft (4) comprises an upper shaft (41), a lower shaft (42) and a sliding bearing (43) which are coaxially arranged; the sliding bearing (43) is disposed between the upper shaft (41) and the lower shaft (42); an outer ring of the sliding bearing (43) is fixedly connected to the stator (3); and an inner ring of the sliding bearing (43) is fixedly connected to the upper shaft (41) and the lower shaft (42).

5. The double-axle underwater motor with single cable lead-out for wells according to claim 1 is characterized in that: An upper coupling (15) and a lower coupling (16) are respectively fixedly connected to both ends of the transmission shaft (4).

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