Static balance method of turbine runner balance equipment

Abstract

The invention discloses a static balance method for water turbine runner balance equipment, belongs to the technical field of static balance, and aims to solve the problem that the coaxiality between a ball seat support and a convex ball of the existing water turbine runner balance equipment cannot be ensured. The butt joint sleeve comprises an outer taper sleeve and an inner taper sleeve, the inner circumference of the outer taper sleeve and the outer circumference of the inner taper sleeve are conical surfaces which are gradually converged from bottom to top, the conicity is the same, and when the butt joint sleeve is used for aligning the supporting sleeve and the ball seat support to be coaxial, the outer taper sleeve and the inner taper sleeve are separated firstly, so that the inner circumference of the inner taper sleeve is in sliding fit with the outer circumference of the ball seat support; the outer periphery of the outer taper sleeve is matched with the inner periphery of the supporting sleeve, then the inner taper sleeve is pushed upwards, meanwhile, the balance assembly to be measured falls, the inner peripheral conical surface of the outer taper sleeve abuts against the outer peripheral conical surface of the inner taper sleeve in an attached mode, and therefore the convex ball and the ball seat support can be kept coaxial simply and efficiently. And measurement errors caused by deviation of the gravity center of the to-be-measured balance assembly from the ball seat supporting axis are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of static balancing, and in particular relates to a static balancing method for a turbine runner balancing device. Background Art

[0002] The runner is the core component of a hydraulic turbine. To ensure smooth operation, the runner undergoes a static balancing test after manufacture, and the runner counterweight is adjusted based on the test results. Chinese invention patent publication number CN119245930A discloses a method for static balancing a pump-turbine runner. This method essentially allows for calibration of the turbine runner's counterweight using balancing equipment.

[0003] Due to the existence of manufacturing deviations, it is even more necessary to ensure the balance of the balancing equipment before balancing and calibrating the turbine runner. Otherwise, the measured results of the static balance of the runner at this stage will be inaccurate, and the runner will not be able to truly reach a balanced state after static balancing, which will bring great hidden dangers to the long-term stable operation of the turbine unit.

[0004] The balance of the balancing equipment can be measured and calibrated through the method disclosed in the invention patent with publication number CN119245930A, but there is still a problem, that is, the coaxiality between the ball seat support and the convex ball cannot be guaranteed. When the convex ball and the ball seat support are matched, the supporting force applied by the ball seat support to the convex ball may not be vertically upward, causing the center of gravity of the convex ball and components such as the support sleeve to deviate from the axis of the ball seat support, resulting in a balance deviation. Summary of the Invention

[0005] The present invention aims to provide a method for static balancing a turbine runner balancing device to solve the problem of the inability to ensure coaxiality between the ball seat support and the convex ball in existing turbine runner balancing devices. The technical solution adopted by the present invention is as follows:

[0006] A method for static balancing a turbine runner balancing device, the balancing device comprising a support sleeve, a convex ball, a flange, a ball seat support, and a plurality of synchronous cylinders, one end of the support sleeve being provided with a sealing end wall, the other end of the support sleeve being provided with a flange, a spherical groove being coaxially provided on the upper end surface of the ball seat support, the spherical surface of the spherical groove being adapted to the spherical surface of the convex ball, the balancing method comprising the following steps:

[0007] Step 1: Define the end surface of the flange facing the sealing end wall as the support plane, set the sealing end wall of the support sleeve downward, and place it on the first square boxes, so that the first square boxes are all supported on the lower side of the support plane and the sealing end wall is suspended in the air;

[0008] Step 2: Place the convex ball and the connecting post on the sealing end wall, and connect the convex ball, the connecting post and the support sleeve coaxially;

[0009] Step 3: A third convex stop is provided on one end surface of the flange, and the third convex stop is set downward and placed on the plurality of second square boxes so that the inner hole of the flange is located between the plurality of second square boxes;

[0010] Step 4: First, lift the assembled connecting column, convex ball and support sleeve, and pass them through the flange so that the outer periphery of the support sleeve fits with the inner hole of the flange, and then connect the flange with the flange using a plurality of first bolts;

[0011] Step 5: Turn the assembled connecting column, convex ball, support sleeve and flange 180 degrees, so that the sealing end wall faces upward and the convex ball faces downward;

[0012] Step 6: First, lift the flipped connecting column, convex ball, support sleeve and flange to the top of the ball seat support and several synchronous cylinders, align them through the docking sleeve, make the support sleeve and the ball seat support coaxial, and then let the flange fall on the piston rods of several synchronous cylinders;

[0013] Step 7: Remove the docking sleeve to form a uniform annular gap between the support sleeve and the ball seat support;

[0014] Step 8: Insert the plurality of second bolts into the plurality of flange holes of the flange one by one, and the support sleeve, the first screw, the convex ball, the connecting column, the plurality of first bolts, the plurality of second bolts and the flange form a balance assembly to be tested;

[0015] Step 9: Inject high-pressure oil into the spherical groove and lower the piston rods of several synchronous cylinders until the piston rods are all separated from the flanges. The balancing component to be tested is floated by the high-pressure oil film between the convex ball and the spherical groove;

[0016] Step 10: Define the flange end face provided with the third convex stop as a measuring plane, detect the inclination of the measuring plane, and determine the eccentric weight and orientation of the balancing assembly to be measured in step 9 according to the inclination of the measuring plane;

[0017] Step 11: Raise the piston rods of several synchronous cylinders and lift the flanges synchronously again;

[0018] Step 12: Process weight-reducing holes on the flange at the heavier part;

[0019] Step 13: Repeat steps 9 to 12 until the component floated by the high-pressure oil film in step 9 is floated and the measuring plane reaches a horizontal state, thus completing the static balance of the balancing device.

[0020] Furthermore, the number of the first square boxes is two.

[0021] Furthermore, the support sleeve is a 20SiMn cast steel component, the convex ball is a 20SiMn cast steel component, and the connecting column is a 45# steel component.

[0022] Furthermore, the convex ball is a hemispherical component, the planar end of the convex ball is provided with a second convex stop, one end of the connecting column is provided with a second concave stop, the second convex stop cooperates with the second concave stop, a first concave stop is provided on the end surface of the sealing end wall facing the inner cavity of the support sleeve, the other end of the connecting column is provided with a first convex stop, the first concave stop cooperates with the first convex stop.

[0023] Furthermore, the diameters of the first convex stop and the second convex stop are the same, and the diameters of the first concave stop and the second concave stop are the same.

[0024] Furthermore, a countersunk hole is provided on the end face of the sealing end wall facing away from the inner cavity of the support sleeve. The countersunk hole is coaxially connected to the first concave stop through a first through hole. A second through hole is provided on the connecting column, and a threaded hole is provided on the second convex stop. The first screw passes through the first through hole and the second through hole in sequence and is connected to the threaded hole. The thread specification of the first screw is M30.

[0025] Furthermore, the number of the second square boxes is two.

[0026] Furthermore, there are three synchronous cylinders, which are evenly distributed around the periphery of the ball seat support.

[0027] Furthermore, the number of the second bolts is eight, and the eight second bolts are coaxially arranged in a one-to-one correspondence with the eight flange holes.

[0028] Furthermore, the docking sleeve includes an outer tapered sleeve and an inner tapered sleeve. The inner periphery of the outer tapered sleeve and the outer periphery of the inner tapered sleeve are both conical surfaces that gradually converge from bottom to top and have the same taper. When the support sleeve is aligned to be coaxial with the ball seat support through the docking sleeve, the outer tapered sleeve and the inner tapered sleeve are first separated, so that the inner periphery of the inner tapered sleeve and the outer periphery of the ball seat support are slidably matched, and the outer periphery of the outer tapered sleeve is matched with the inner periphery of the support sleeve. Then, the inner tapered sleeve is pushed up, and at the same time, the balancing assembly to be tested is dropped so that the inner tapered surface of the outer tapered sleeve and the outer tapered surface of the inner tapered sleeve fit together and offset each other.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] After installing the second bolt securing the turbine runner, the balancing assembly to be tested is statically balanced, and weight-reducing holes are machined on the flange based on the weight imbalance. This balances the components of the balancing equipment that float during runner balancing, thus preventing errors in the turbine runner balancing results caused by imbalance in the balancing equipment. Assembly is convenient, operation is simple, and balancing accuracy is high. Aligning the axis of the convex ball and the ball socket support using the docking sleeve allows the convex ball and the ball socket support to fit with relatively precise coaxiality. This simple and efficient alignment avoids measurement errors caused by the center of gravity of the balancing assembly to be tested deviating from the axis of the ball socket support. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of step 1 of the present invention;

[0032] Figure 2 It is a structural diagram of the support sleeve;

[0033] Figure 3 It is a structural diagram of the connecting column;

[0034] Figure 4 It is a schematic diagram of the structure of a convex sphere;

[0035] Figure 5 It is a schematic diagram of step four of the present invention;

[0036] Figure 6 It is a structural diagram of the flange;

[0037] Figure 7 It is a schematic diagram of step six of the present invention;

[0038] Figure 8 It is an exploded schematic diagram of the docking sleeve;

[0039] Figure 9 yes Figure 7 AA cross-sectional view;

[0040] Figure 10 This is a schematic diagram showing that existing turbine runner balancing equipment cannot ensure that the convex ball and the ball seat support are coaxial.

[0041] In the figure, 1-support sleeve; 2-first square box; 3-first screw; 4-convex ball; 5-connecting column; 6-support plane; 7-first concave stop; 8-first through hole; 9-countersunk hole; 10-second through hole; 11-threaded hole; 12-second convex stop; 13-second concave stop; 14-first convex stop; 15-second square box; 16-third convex stop; 17-first bolt; 18-ball seat support; 19-synchronizing cylinder; 20-piston rod; 21-second bolt; 22-flange hole; 23-spherical groove; 24-measuring plane; 25-flange; 26-docking sleeve; 27-outer tapered sleeve; 28-inner tapered sleeve; 29-sealing end wall; 30-flange. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described below using specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0043] The connections mentioned in the present invention are divided into fixed connections and detachable connections. The fixed connection refers to a non-detachable connection, including but not limited to conventional fixed connection methods such as hem connection, rivet connection, adhesive connection, and welding connection. The detachable connection refers to but not limited to conventional detachable connection methods such as bolt connection, snap connection, pin connection, and hinge connection. When the specific connection method is not clearly specified, it is assumed that at least one connection method can be found among the existing connection methods to achieve the function. Those skilled in the art can choose according to their needs. For example, a welded connection is selected for a fixed connection, and a bolted connection is selected for a detachable connection.

[0044] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are provided to explain the present invention, but the present invention is not limited to the following embodiments.

[0045] Example: Figures 1 to 10 As shown, a static balancing method for a turbine runner balancing device is provided. The balancing device includes a support sleeve 1, a convex ball 4, a flange 25, a ball seat support 18, and a plurality of synchronous cylinders 19. One end of the support sleeve 1 is provided with a sealing end wall 29, and the other end of the support sleeve 1 is provided with a flange 30. A spherical groove 23 is coaxially provided on the upper end surface of the ball seat support 18. The spherical surface of the spherical groove 23 is adapted to the spherical surface of the convex ball 4. The balancing method includes the following steps:

[0046] Step 1: Define the end surface of the flange 30 facing the sealing end wall 29 as the support plane 6, set the sealing end wall 29 of the support sleeve 1 downward, and place it on the first square boxes 2, so that the first square boxes 2 are all supported on the lower side of the support plane 6, and the sealing end wall 29 is suspended in the air;

[0047] Step 2: Place the convex ball 4 and the connecting post 5 on the sealing end wall 29 so that they are aligned with each other, and connect the convex ball 4, the connecting post 5 and the support sleeve 1 coaxially;

[0048] Step 3: A third convex stop 16 is provided on one end surface of the flange 25. The third convex stop 16 is set downward and placed on the plurality of second square boxes 15 so that the inner hole of the flange 25 is located between the plurality of second square boxes 15.

[0049] Step 4: First, lift the assembled connecting column 5, convex ball 4 and support sleeve 1, and pass them through the flange 25 so that the outer periphery of the support sleeve 1 fits with the inner hole of the flange 25, and then connect the flange 30 to the flange 25 with a plurality of first bolts 17;

[0050] Step 5: Flip the assembled connecting column 5, convex ball 4, support sleeve 1 and flange 25 180° so that the sealing end wall 29 faces upward and the convex ball 4 faces downward;

[0051] Step 6: First, lift the flipped connecting column 5, convex ball 4, support sleeve 1 and flange 25 above the ball seat support 18 and the synchronous cylinders 19. Align them with the docking sleeve 26 so that the support sleeve 1 and the ball seat support 18 are coaxial. Then, place the flange 25 on the piston rod 20 of the synchronous cylinders 19.

[0052] Step 7: Remove the docking sleeve 26 to form a uniform annular gap between the support sleeve 1 and the ball seat support 18;

[0053] Step 8: Insert the plurality of second bolts 21 into the plurality of flange holes 22 of the flange 25 one by one. The support sleeve 1, the first screw 3, the convex ball 4, the connecting column 5, the plurality of first bolts 17, the plurality of second bolts 21 and the flange 25 form a balance assembly to be tested.

[0054] Step 9: Inject high-pressure oil into the spherical groove 23 and lower the piston rods 20 of the synchronous cylinders 19 until the piston rods 20 are all separated from the flange 25. The balancing component to be tested is floated by the high-pressure oil film between the convex ball 4 and the spherical groove 23.

[0055] Step 10: Define the end surface of the flange 25 provided with the third convex stop 16 as the measuring plane 24, detect the inclination of the measuring plane 24, and determine the eccentric weight and orientation of the balancing assembly to be measured in step 9 based on the inclination of the measuring plane 24;

[0056] Step 11: Raise the piston rods 20 of the synchronous cylinders 19 and re-synchronize and lift the flanges 25;

[0057] Step 12: Processing weight-reducing holes on flange 25 at the weighted part;

[0058] Step 13: Repeat steps 9 to 12 until the component is floated by the high-pressure oil film in step 9 and the measuring plane 24 reaches a horizontal state, thus completing the static balance of the balancing device.

[0059] The number of the first square boxes 2 is two.

[0060] The support sleeve 1 is a 20SiMn cast steel component, the convex ball 4 is a 20SiMn cast steel component, and the connecting column 5 is a 45# steel component.

[0061] The convex ball 4 is a hemispherical component with a second convex stop 12 on its flat end and a second concave stop 13 at one end of the connecting post 5. The second convex stop 12 and the second concave stop 13 are engaged. A first concave stop 7 is formed on the end surface of the sealing end wall 29 facing the inner cavity of the support sleeve 1. A first convex stop 14 is formed at the other end of the connecting post 5. These first concave stop 7 and the first convex stop 14 engage with each other. This improves the coaxiality of the convex ball 4, the connecting post 5, and the support sleeve 1, making assembly convenient and efficient.

[0062] The diameters of the first convex stop 14 and the second convex stop 12 are the same, and the diameters of the first concave stop 7 and the second concave stop 13 are the same.

[0063] A countersunk hole 9 is provided on the end face of the sealing end wall 29 on the side facing away from the inner cavity of the support sleeve 1. The countersunk hole 9 is coaxially connected to the first concave stop 7 through the first through hole 8. A second through hole 10 is provided on the connecting column 5, and a threaded hole 11 is provided on the second convex stop 12. The first screw 3 passes through the first through hole 8 and the second through hole 10 in sequence and is connected to the threaded hole 11. The thread specification of the first screw 3 is M30.

[0064] The number of the second square boxes 15 is two.

[0065] There are three synchronous cylinders 19 , which are evenly distributed around the outer periphery of the ball seat support 18 in the circumferential direction.

[0066] There are eight second bolts 21 , and the eight second bolts 21 are coaxially arranged in a one-to-one correspondence with the eight flange holes 22 .

[0067] When the turbine runner is balanced, the docking sleeve 26 is engaged with the runner to realize the balance detection and calibration of the turbine runner. The docking sleeve 26 includes an outer tapered sleeve 27 and an inner tapered sleeve 28. The inner periphery of the outer tapered sleeve 27 and the outer periphery of the inner tapered sleeve 28 are both conical surfaces that converge gradually from bottom to top, and the taper is the same. When the support sleeve 1 is aligned to be coaxial with the ball seat support 18 through the docking sleeve 26, the outer tapered sleeve 27 and the inner tapered sleeve 28 are first separated, so that the inner periphery of the inner tapered sleeve 28 is slidably matched with the outer periphery of the ball seat support 18, and the outer periphery of the outer tapered sleeve 27 is matched with the inner periphery of the support sleeve 1, and then the inner tapered sleeve 28 is pushed up, and at the same time, the balance component to be tested is dropped, so that the inner conical surface of the outer tapered sleeve 27 and the outer conical surface of the inner tapered sleeve 28 are fitted and offset.

[0068] After installing the second bolt 21 for securing the turbine runner, the balancing assembly to be tested is statically balanced, and weight-reducing holes are machined in the flange 25 according to the weight imbalance. This allows the components of the balancing equipment involved in balancing the runner to be balanced, thus avoiding errors in the turbine runner balancing results caused by imbalance in the balancing equipment. Assembly is convenient, operation is simple, and balancing accuracy is high. Aligning the axis of the protruding ball 4 and the ball seat support 18 via the docking sleeve 26 allows the protruding ball 4 and the ball seat support 18 to fit with relatively precise coaxiality. This simple alignment is highly efficient and avoids measurement errors caused by the center of gravity of the balancing assembly to be tested deviating from the axis of the ball seat support 18.

[0069] The above embodiments are merely illustrative of the present invention and do not limit its scope of protection. Those skilled in the art may make partial changes thereto, which are within the scope of protection of the present invention as long as they do not exceed the spirit of the present invention.

Claims

1. A method for static balancing of a turbine runner balancing device, the balancing device comprising a support sleeve (1), a convex ball (4), a flange (25), a ball seat support (18) and a plurality of synchronous cylinders (19), one end of the support sleeve (1) being provided with a sealing end wall (29), the other end of the support sleeve (1) being provided with a flange (30), a spherical groove (23) being coaxially provided on the upper end surface of the ball seat support (18), the spherical surface of the spherical groove (23) being adapted to the spherical surface of the convex ball (4), and characterized in that: The balancing method comprises the following steps: Step 1: define the end surface of the flange (30) facing the sealing end wall (29) as the support plane (6), set the sealing end wall (29) of the support sleeve (1) downward, and place it on the plurality of first square boxes (2), so that the plurality of first square boxes (2) are all supported on the lower side of the support plane (6), and the sealing end wall (29) is suspended in the air; Step 2: Place the convex ball (4) and the connecting column (5) on the sealing end wall (29) so that they are in contact with each other, and connect the convex ball (4), the connecting column (5) and the support sleeve (1) coaxially; Step 3: A third convex stop (16) is provided on one end surface of the flange (25), and the third convex stop (16) is set downward and placed on the plurality of second square boxes (15), so that the inner hole of the flange (25) is located between the plurality of second square boxes (15); Step 4: First, lift the assembled connecting column (5), convex ball (4) and support sleeve (1), and pass them through the flange (25) so that the outer periphery of the support sleeve (1) fits with the inner hole of the flange (25), and then connect the flange (30) and the flange (25) through a plurality of first bolts (17); Step 5: Turn the assembled connecting column (5), convex ball (4), support sleeve (1) and flange (25) 180 degrees so that the sealing end wall (29) faces upward and the convex ball (4) faces downward; Step 6: First, lift the turned-over connecting column (5), convex ball (4), support sleeve (1) and flange (25) to the top of the ball seat support (18) and the plurality of synchronous cylinders (19), align them through the docking sleeve (26) so that the support sleeve (1) and the ball seat support (18) are coaxial, and then the flange (25) falls on the piston rod (20) of the plurality of synchronous cylinders (19); Step 7: Remove the docking sleeve (26) to form a uniform annular gap between the support sleeve (1) and the ball seat support (18); Step 8: Insert the plurality of second bolts (21) into the plurality of flange holes (22) of the flange (25) in a one-to-one correspondence, and the support sleeve (1), the first screw (3), the convex ball (4), the connecting column (5), the plurality of first bolts (17), the plurality of second bolts (21) and the flange (25) form a balance assembly to be tested; Step 9: Inject high-pressure oil into the spherical groove (23), lower the piston rods (20) of the synchronous cylinders (19), until the piston rods (20) are all separated from the flange (25), and the balancing component to be tested is floated by the high-pressure oil film between the convex ball (4) and the spherical groove (23); Step 10: defining the end face of the flange (25) provided with the third convex stop (16) as the measuring plane (24), detecting the inclination of the measuring plane (24), and determining the eccentric weight and orientation of the balancing assembly to be measured in step 9 according to the inclination of the measuring plane (24); Step 11: Raise the piston rods (20) of the synchronous cylinders (19) and re-synchronize the lifting of the flanges (25); Step 12: Processing a weight-reducing hole on the flange (25) at the weighted part; Step 13: Repeat steps 9 to 12 until the component in step 9 is floated by the high-pressure oil film and the measuring plane (24) reaches a horizontal state, thus completing the static balance of the balancing device.

2. A method for static balancing of a turbine runner balancing device according to claim 1, characterized in that: The number of the first square boxes (2) is two.

3. The static balancing method for a water turbine runner balancing device according to claim 1, characterized in that: The support sleeve (1) is a 20SiMn cast steel component, the convex ball (4) is a 20SiMn cast steel component, and the connecting column (5) is a 45# steel component.

4. The static balancing method for a water turbine runner balancing device according to claim 1, characterized in that: The convex ball (4) is a hemispherical component. The plane end of the convex ball (4) is provided with a second convex stop (12). One end of the connecting column (5) is provided with a second concave stop (13). The second convex stop (12) and the second concave stop (13) are matched. A first concave stop (7) is provided on the end surface of the sealing end wall (29) facing the inner cavity of the support sleeve (1). The other end of the connecting column (5) is provided with a first convex stop (14). The first concave stop (7) and the first convex stop (14) are matched.

5. The static balancing method for a water turbine runner balancing device according to claim 4, characterized in that: The diameters of the first convex stop (14) and the second convex stop (12) are the same, and the diameters of the first concave stop (7) and the second concave stop (13) are the same.

6. The static balancing method for a water turbine runner balancing device according to claim 4, characterized in that: A countersunk hole (9) is provided on the end surface of the sealing end wall (29) on the side away from the inner cavity of the support sleeve (1). The countersunk hole (9) is coaxially connected to the first concave stop (7) through the first through hole (8). A second through hole (10) is provided on the connecting column (5). A threaded hole (11) is provided on the second convex stop (12). The first screw (3) passes through the first through hole (8) and the second through hole (10) in sequence and is connected to the threaded hole (11). The thread specification of the first screw (3) is M30.

7. The static balancing method for a hydraulic turbine runner balancing device according to claim 1, characterized in that: The number of the second square boxes (15) is two.

8. The static balancing method for a water turbine runner balancing device according to claim 1, characterized in that: The number of the synchronous cylinders (19) is three, and the three synchronous cylinders (19) are evenly distributed on the outer periphery of the ball seat support (18) in the circumferential direction.

9. The static balancing method for a water turbine runner balancing device according to claim 1, characterized in that: The number of the second bolts (21) is eight, and the eight second bolts (21) are coaxially arranged in a one-to-one correspondence with the eight flange holes (22).

10. A static balancing method for a water turbine runner balancing device according to any one of claims 1 to 9, characterized in that: The docking sleeve (26) includes an outer tapered sleeve (27) and an inner tapered sleeve (28). The inner periphery of the outer tapered sleeve (27) and the outer periphery of the inner tapered sleeve (28) are both tapered surfaces that gradually converge from bottom to top, and have the same taper. When the support sleeve (1) and the ball seat support (18) are aligned coaxially by the docking sleeve (26), the outer tapered sleeve (27) and the inner tapered sleeve (28) are first separated, so that the inner periphery of the inner tapered sleeve (28) and the outer periphery of the ball seat support (18) are slidably matched, and the outer periphery of the outer tapered sleeve (27) is matched with the inner periphery of the support sleeve (1), and then the inner tapered sleeve (28) is pushed up, and at the same time, the balance assembly to be tested is dropped, so that the inner tapered surface of the outer tapered sleeve (27) and the outer tapered surface of the inner tapered sleeve (28) are fitted and offset.

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