Installation layout for two coaxial shaft lines  


A set with two concentric shafts, the inner shaft projects beyond the axis of the outer sleeve, a support of the joint between the axes has a conical shape and is supported by a spacer mounted on the outer shaft between a mounting nut the front end of the outer shaft and a bearing, so that the nut is accessible to be unscrewed through the space between the two axes, thus allowing the outer shaft to be disassembled. The invention can be applied to the front bearings of the axes of the high pressure turbine gas and makes it possible to remove the high pressure body from the rear, without disassembling the equipment, such as a fan in the front of the machine or prevent the installation of a gear.
Cross Reference to Related Applications
This document is a continuation of U.S. application Being. No. 10/476, 372, filed on March 24, 2004 now abandoned, which is a National Stage of PCT Application No. PCT/FR02/01506, filed on May 2, 2002. This application is also based on and claims the benefit of priority from prior French Patent Application No. 01/05900, filed on May 3, 2001. The contents of U.S. Application Being. No. 10/476, 372 incorporated herein by reference in its entirety.
Background of the Invention
1. Field of the Invention
This invention relates to an assembly for the installation of two coaxial shafts, in particular a so-called low-pressure shaft as shown in Fig. 1, which connects the low-pressure compressor 1 to the low-pressure turbine 2 in a gas turbine surrounded by a high pressure shaft that connects the high pressure compressor 3 to the high pressure turbine 4. Throughout this specification, the front of the machine is on the left side of the drawing and the rear of the machine is on the right.
Two. Description of Related Art
In this type of machine, the shaft 15 projects (low pressure) internal beyond the front of the outer shaft 16 (high pressure) and can terminate at one end of shaft 5 which carries a large volume ventilator 6 on large blades are mounted for download radio auxiliary air stream 7 surrounding the main gas stream 8. If there is an accidental breakage in the fan, there will be a severe equilibrium mass outside the inner shaft 15. Therefore, some work should be done. First, a bearing 9, also referred to as bearing number 1, right at the front of the inner shaft 15, can be made frangible fuse or in other words, can be installed on a substrate of low resistance 10 which is designed to break as soon as a mass balance develops outside, so that the large forces that are generated resulting then not transmitted to the rest of the stator structure. The end of the shaft 5 is then free to tilt under the effect of moving the mass out of balance until the assembly formed by the fan 6 is moved to a new equilibrium position in the rotation, without necessarily causing any further damage until the machine stops. The end of the shaft 5 is tilted about the other bearing 17, also referred to as having No. 2, behind the front bearing 9 which supports the rear end of the tip of the shaft 5 and a main shaft portion 15 inside. This bearing 17 controls the axial position of inner shaft 15.
A takeoff gear 20, specially designed for starting the machine and driven by a drive shaft 25 perpendicular to axes 15 and 16, must be placed between the bearing 17 and still another bearing 18, also referred to as having number 3 provides support for the front end of the outer shaft 16. The bearing 17, being on the possible backward to improve the dynamic resistance of the inner shaft 15, a bearing 18 is separated by just enough space to contain the takeoff gear 20. A nut is screwed around the forward end of the outer shaft 16, abuts against the bearing 18 to stop the axial movement. This nut (shown in Figure 2.) Which extends forward from the bearing 18 and is disposed just above the takeoff gear 20, is difficult to access, particularly because a sleeve holder board should be placed behind the bearing 17 immediately before the nut. Sleeve overlaps the front end of outer shaft 16 and an inner shaft portion 15 to create a seal between them. Removing the high pressure shaft 16 for maintenance usually only possible after removing the machine in front of the nut, and in particular the removal of the fan 6, so that the nut can be reached and unscrewing.
French Patent 2,783,579 describes an assembly by which the nut can be unscrewed from behind by using a special tool which is inserted into the annular space between the shafts. This is more convenient, despite the fact that this space is narrow, since there is no need for any significant disassembly of the machine elements to remove the high pressure shaft, but in this patent the nut is screwed inside the outer shaft which is wrapped around the shaft in more conventional designs, which changes all the design of the front end of the shaft and can introduce other disadvantages. In the present invention, it is proposed another solution to provide easy access from the back of the machine to the retaining nut outer shaft 16 without any major change in the design. Some modifications to the parts of the machine that surrounds the nut are still necessary, but you will see that they are concerned primarily with the sealed-off devices, so that the design can be altered more easily.
In its most general form, the representative set of the invention comprises inner and outer coaxial shafts, part of the forward inner shaft projects beyond a forward end of the outer shaft, a sleeve surrounding the axle and supporting an associated seal with each of the shafts, a bearing supporting the external shaft near the front end, and a bearing retention nut screwed around the front end, a spacer with a fitting portion slipped around the outer shaft and clamped between the nut and the bearing, and a sealing portion in which the seal associated with the external shaft rubs, the sealing portion is disposed around the nut.
The advantages and other aspects of the invention will be discovered after reading the review of the following figures:
. Figure 1, already described, is a general view of a gas turbine;
. Figure 2 shows the conventional assembly not resolved the problems of access to the nut above;
. Figure 3 shows an assembly according to the invention;
. Figure 4 shows a view of another assembly according to the invention.
. Figure 2 shows a portion of the inner shaft 15, the front end of the outer shaft 16, one end of the (number 2) bearing 17, the (number 3) bearing 18, the nut assembly 19 bearing 18, the take-off gear 20 a crown wheel 21 meshed with the take-off gear 20 and retained around the outer shaft 16 and between the nut 19 and the bearing 18, the support sleeve joint 22, and the two joints 23 and 24, rubbing on adjacent portions of the shafts 15 and 16. Environment takeoff sprocket 20 comprises a drive shaft 25 connected in rotation to the take-off gear 20 engaged grooves 26 and a gear hub 27 off 20, a pair of bearings 28 and 29 engaged around Hub 27, a housing 30 bolted to an extension 31 of sleeve 22, which is connected (on the right in the figure) to a stator housing 32, a shell 33 screwed into the housing 30 and in which the bearing 29 remote from takeoff gear 20 is retained while the bearing 28 closer to the take-off gear 20 is retained in the hub 27 and slides in the housing 30, collars 34 and 35 of bearing housing 28 and housing 33 which contains 30 are bolted to it to hold the bearings 28 and 29 in a fixed position along the axis 27. The mounting screws are not shown to simplify the drawing. In this case, the bearing 28 is a ball bearing and the bearing 29 is a roller bearing without an inner race and the rollers bear directly on the hub 27.
It is worth mentioning the installation method in this assembly off mechanism 20 after the nut 19 is screwed around the outer shaft 16. Takeoff gear 20, the bearing 28 closer to it, and the housing 30 are installed by fixing the casing 30 in the housing 32, the housing 33 and the bearing 29 is installed by fixing the housing shell 30 and seal support sleeve 22 is attached to housing 30 by sliding it back. Finally, the shaft 25 is inserted into the hub 27. Seen that the nut 19, and surrounded by other parties has become inaccessible unless performed major disassembly. Because the stamp 24 is rubbed on a lip 14 of the outer shaft 16 which extends forwardly from the nut 19 and the nut 19 is screwed around the outer shaft 16, the support sleeve seal 22 separates completely from the nut 19 annular space 13 between the shafts 15 and 16 through which the nut 19 may be unscrewed from the rear of the machine with conventional dedicated tool comprising claws.
. 3 illustrates a first embodiment of the invention. The description is made by comparing with Fig. 2 shows the same alterations only. . Figure 3 shows a first support sleeve modified seal element 38 is identified as having a conical shape and the seal, now identified as element 39, outer shaft 16 now has a diameter larger than the (unchanged) the seal 23 inside the shaft 15, the seal 39 does not actually rub on the outer shaft 16, but rather a seal contact surface 41 of a spacer 40 mounted on the outer shaft 16 and having a contact surface thrust 42 fitted around the outer shaft 16 and compressed between the nut 19 and the first crown 21.
The result of this arrangement is that the contact surface 41 and the sealing sleeve 38 surrounding the nut 19 extending forwardly thereof instead hence the nut 19 becomes accessible from the rear of the machine. Dedicated tool can slide into the annular space 43 between the shafts 15 and 16 to reach the nut 19 is at the front end of the shaft 16, the lip 14 towards the front being replaced by the sealing contact surface surrounding 41. For the sake of completeness, there is shown a conventional locking portion 44 of the nut 19 comprising crab teeth that penetrate into the nut 19 and the outer shaft 16 to prevent any relative rotation of the nut 19 and the outer edge 16 when installed, the locking piece 44 is in the form of a split ring made of an elastic material so that it can be opened during assembly.
Some agreements Progress takeoff near 20 are applied to adapt the design to the modified form of the seal support sleeve 38. Yet there are two bearings 28 and 29 for supporting the hub support 27 takeoff gear 20 and housing 30 fixed to the extension sleeve 31 of seal support 38 and the housing 32, but now the shell 33 is replaced by a different shell 45 extending around the two bearings 28 and 29 and still includes the collar 35 to fix the housing 30.
The whole is different from the set in Fig. Two. After the housing 30 containing the takeoff gear 20 fitted with the bearing closer (in this case the roller bearing 29) has been fixed, the takeoff gear 20 lying on a bottom surface of the housing 30, the sleeve Seal holder 38 is slid back over the sprocket 20 and secured to the housing 30. Shell 45 equipped with the farthest from the bearing for the takeoff gear 20 (in this case the ball bearing 28) is then inserted into the bore in the housing 30 and around the hub 27 and the bearing 29. Bearing 28 carries a spacer ring 51 finally touches the other bearing 29 during this movement, which pushes up and lifts the takeoff gear 20. When the collar 35 stops in contact with the housing 30, the takeoff gear 20 meshing with the sprocket 21. The drive shaft 25 is then finally installed.
. 4 shows a variant in which the bearings 28 and 29 occupy the same positions as in Fig. 2 design in which the shell of Figure 33. 2 is used, but the collar 34 of the bearing 28 positioned on an edge of the housing 30 is replaced by a collar 46 positioned below the edge and the collar 35 of the housing 33 into contact with the underside of the neck 46. Assembly takes approximately the same shape as in Fig. 3, except that the bearings 28 and 29 are installed after the takeoff gear 20 has been put into the box 30.
The innovation of the assembly according to the invention can be explained as follows. Access to the nut 19 from the front, which was the only possible in conventional designs, requires sliding the support sleeve joint 22 in Fig. 2 forwards, away from the housing 30. This movement of the support sleeve of the board in the forward direction is no longer useful to the invention, and it is even impossible as the cuff wide rear board support 38 could interfere with take-off gear teeth 20. Therefore, also be a problem to mount the housing 30 if the sleeve of seal support 38 moves forward from its front edge high stopped in contact with the flared rear of the housing. Therefore, in the embodiment of FIG. 3, the sleeve seal support 38 is pulled back during assembly of the housing 30 and the takeoff gear 20, the mounting flange 48 is stopped in contact with the casing 30 in the back, unlike the Fig. Two. The assembly does not cause any difficulty as long as the takeoff gear 20 can be lowered to the bottom of the housing 30 so that it does not collide with the mounting flange 48 or other parts of the seal support sleeve 38 before it is in its final position, which is possible if the shell 45 below the housing 30, mounted to the housing 30 with an upward movement, the two support bearings 28 and 29 so that the takeoff gear 20 can be lowered below sleeve seal support 38 as soon as the shell 45 is removed.                                             
Mounting Fig. 3 with a single housing 45 for the bearing 28 provided by the takeoff gear 20 with the thrust bearing and the sliding bearing 29 in the vertical direction, it is simpler and probably more rigid, but makes it necessary to reverse the conventional positions of the bearings 28 and 29, and the whole can be more complicated due to the larger size of the shell 45. This is why the assembly in Fig. 4, the main difference of the prior art is the position of the collar 46, has merits.


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