1 Title of the Invention
Shaft Alignment and Torque Tightening Tool Set for Aero Engine
Application,
2 Field of the invention
The invention relates to mechanical engineering field and specifically to
assembly of gas turbine engines where one shaft is to be tightened
against another shaft with a minimum torque and simultaneously be
oriented to match with a third shaft.
3 Background of the Invention
Current practice to align Locking Shaft [040] simultaneously with
Intermediate Shaft [020] and Tie Rod [030] is by incremental torqueing.
A torqueing tool (with internal splines at one end, matching to external
splines [031] of Tie Rod [030]) to be applied to tighten Tie Rod [030]
against CT Shaft [010] and Intermediate Shaft [020]. After achieving
minimum desired torque value, the tool to be taken out and Locking Shaft
[040] to be inserted by matching internal splines [041] of Locking Shaft
[040] with external splines [031] of Tie Rod [030]. Locking Shaft [040] is
supposed to be inserted with less depth as external splines [042] of
Locking Shaft [040] would not have matched with internal splines [021] of
Intermediate Shaft [020] under'most probable circumstance
Another tool (with internal splines at one end, matching to external splines
[042] of Locking Shaft [040]) to be applied to tighten Tie Rod [030] further,
through Locking Shaft [040] so as to match the external splines [042] of
Locking Shaft [040] with internal splines [021] of Intermediate Shaft [020].
This process is tedious as at every instance it needs to be checked
whether the spline pairs [041 with 031 and 042 with 021] are matched.
else to increase the tightening further. Most of the time the process ends
up with applying more than the required tightening.
The problem of iterative assembly has been addressed by introducing a
set of tools for aero engine assembly.
3.1 Prior Art
Patent TW|632033B has been considered as a prior art, wherein a spline
alignment tool set and a method for combining automobile motor and a
gearbox are disclosed. The patent describes — the spline output structure
of the motor and the spline input structure of the gearbox are positioned
opposite by the tool set so that they can successfully be engaged without
collision.
In the scenario of shaft alignment and applying tightening torque during
aero engine assembly, one splined shaft with thread to be tightened over
another splined shaft with a minimum desired torque and a third splined
shaft to be aligned to both first as well as second shaft through two pairs
of splines simultaneously - unlike the claims in the patent, considered as
prior art, where only one pair of splines to be aligned without any
requirement of applying tightening torque.
The tool set and method. claimed in the said patent, align the output and
input splines to two different casings / bodies to fix their relative position
and the casings / bodies are aligned to each other before assembly.
Whereas, in case of shaft alignment of aero engine assembly, no such
provision is available to use the casing as a reference for alignment. New
precise features can be created to adapt such tool (as claimed in the prior
art patent) but those modifications in part design will increase the
manufacturing complexity, cost & lead time and these increased
parameters will be repetitive with each unit.
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The tool set, as in present invention, is self-aligning to align the splines of
the shafts of aero engine assembly, which‘ eliminates the requirement of
casing reference for alignment. Thus the manufacturing parameters will
remain constant for the engine.
4 Brief Summary of the Invention
The methodology introduced, comprises of the following features
The technology involves holding Intermediate Shaft [020] through internal
splines [021] and apply minimum desired torque on Tie Rod [030] through
external splines [0311 Applied torque to be increased by the least value to
align the tools [050 & 060] with each other which in turn will align the
shafts [020 & 030] such a way that splines [041 & 042] of Locking Shaft
[040] gets aligned to splines [O31 & 021] of Tie Rod [O30] & Intermediate
Shaft [020] simultaneously‘
This eliminates iterative method of assembly and reduces assembly time.
The same set of tools and technology also facilitates to apply tightening
torque on Tie Rod [030] against Intermediate Shaft [020] without any
special feature on the parts.
5 Detail Description of the Drawings
The invention can be better understood by reading the detail description of
the disclosed embodiment followed by the accompanied drawings in
which,
Figure 1: depicts the exploded view of CT shaft [010], Intermediate Shaft
[020] and Tie Rod [030] - to be assembled together.
Figure 2: shows the assembled view of CT shaft [010], Intermediate Shaft
[020] and Tie Rod [030]. It also includes the exploded view of Locking Tool
[050] & Holding Tool [060] required to apply tightening torque on Tie Rod
‘
[030] and align with Intermediate Shaft [020].
Figure 3: represents the assembly of shafts [010, 020 & 030] along with
tools [050 & 060].
Figure 4: describes the alignment of tools [050 & 060] with each other so
as to align the splines [051 & 061].
Figure 5: indicates the alignment of intermediate Shaft [020] with Tie Rod
[030] by aligning splines [021 & 031]. It also includes the exploded view of
Locking Shaft-[040].
Figure 6: indicates final assembly of all shafts [010, 020, 030 & 040].
6 Detail Description of the Invention
The following specification particularly describes the invention and the
manner in which it is to be performed.
Referring to Figure 1, Intermediate Shaft [020] is assembled on CT Shaft
[010] by engaging external splines [022] of Intermediate Shaft [020] into
internal splines [011] of CT Shaft [010] and locked by engaging external
threads [032] of Tie Rod [030] with internal threads [012] of CT Shaft
[010].
Referring to Figure 2 & 3, minimum desired tightening torque is applied on
Tie Rod [030] to ensure locking. A Locking Tool [050] and a Holding Tool
[060] to be used to apply torque. Internal splines [051] of Locking Tool
[050] engages to external splines [631] of Tie Rod [030] and external
splines [061] of Holding Tool [060] engages to internal splines [021] of
Intermediate Shaft [020].
Standard calibrated torque wrench to be connected to socket [053] of
Locking Tool [050] and a standard wrench to be engaged into socket [063]
of Holding Tool [060]. Standard calibrated torque wrench connected to
Locking Tool [050] will drive Tie Rod [030] through spline pair [031 & 051]
to the desired torque value, while standard wrench engaged in Holding
Tool [060] will give a grip to hold Intermediate Shaft [920] (in turn CT Shaft
[010]) rigidly against applied torque.
At this condition angular orientation is not maintained between
Intermediate Shaft [020] and Tie Rod [030] — i,e. teeth to teeth orientation of internal splines [021] of‘ Intermediate Shaft [020] to external splines
[031] of Tie Rod [030] is not controlled.
Referring to Figure 2 & 4, Locking Tool [050] is having a square flat
feature [052] where one face of the square [052] is perfectly aligned to
mid-plane of two teeth (blank space) of internal splines [051]. Similarly,
Holding Tool [060] is having a square slot [062] (matching with square flat
[052] of Locking Tool [050]) where one face of the square slot [062] is
perfectly aligned to mid-plane of one tooth of external splines [061]. If the
square flat [052] of Locking Tool [050] gets perfectly aligned to square slot
[062] of Holding Tool [060], mid—plane of two teeth of internal splines [051]
automatically aligns to mid-plane of one tooth of external splines [061] by
virtue of their positions — i.e. both splines [051 & 061] of the tools [050 & 060] are aligned to each other.
Referring to Figure 3 & 5, after applying minimum desired torque on Tie
Rod [030], the torque value to be increased by the least required to align
the square fiat [052] of Locking Tool [050] to square slot [062] of Holding
Tool [060] — to ensure alignment of the squares [052 & 062], the Holding
Tool [060] may be pulled out of the assembly passing over the Locking
Tool [050], Square flat [052] of Locking Tool [050] will allow the Holding
Tool [060] to come out only if the square slot [062] of Holding Tool [060] is
perfectly aligned to Square fiat [052] of Locking Tool [050]. This ensures
the perfect alignment of splines [051 & 061] with each other as explained
before. As these splines [051 & 061] of the tools [050 & 060] are engaged
in external splines [031] of Tie Rod [030] and internal splines [021] of
Intermediate Shaft [020] respectively, mid—plane of one tooth of external
splines [031] of Tie Rod [030] gets aligned to mid-plane of two teeth of internal splines [021] of Intermediate Shaft [020] — thus angular orientation
is ensured between Intermediate Shaft [020] and Tie Rod [030].
Referring to Figure 5, mid-plane of two teeth of internal splines [041] and
mid-plane of one tooth of external splines [042] of Locking Shaft [040] are
aligned to each other by design. Once the external splines [031] of Tie
Rod [030] aligns to internal splines [021] of Intermediate Shaft [020],
Locking Shaft [040] can be assembled by engaging both splines [O41 &
042] simultaneously with external splines [031] of Tie Rod [030] & internal
splines [021] of Intermediate Shaft [020] (respectively).
Stress analysis have been carried out on Locking Tool [050] & Holding
Tool [060] through ANSYS Finite Element Analysis Tool to check the
structural integrity. Subsequently, detailed drawings of the components
_(set of tools) have been released and the methodology has been
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implemented The assembly processes (applying tightening torque on Tie
Rod [030] and aligning splines [041 & 042] of Locking Shaft [040]) has become simpler (iterative assembly is eliminated). Total cost of assembly
is reduced compared to the existing method as time requirement has been
reduced.
We Claim,
1. Shaft alignment and torque tightening tool set for aero engine
application to apply tightening torque on a Tie Rod [030] against an
Intermediate Shaft [020], and align a Locking Shaft [040] to the
assembled pair of shafts [020 & 030], comprising:
a Holding Tool [060] to arrest the rotation of said Intermediate Shaft
[020]; and
a Locking Tool [050] to tighten said Tie Rod [030] against said
Intermediate Shaft [020] with minimum desired torque. and align the
splines [021 & 031] of said pair of Intermediate Shaft [020] & Tie
Rod [030] so as to match with both splines [O42 & 041] of said
Locking Shaft [040] simultaneously.
2. The said tool set as claimed in Claim 1, wherein said Holding Tool
[060] characterized by:
an external spline [061] matching to internal spline [021] of said
Intermediate Shaft [020];
a square slot [062] for alignment; and
a socket [063] to have provision for inserting a standard wrench.
3. The said tool set as claimed in Claim 1, wherein said Locking Tool
[050] characterized by:
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an internal spline [051] matching to external spline [031] of said Tie
Red [030];
a square flat feature [052] matching to said square slot [062] of said
Holding Tool [060]; and
a socket [053] to have provision for inserting a standard calibrated
torque wrench.