Title of the Invention
Nut Crimping Tool for a Self-Locking Nut used in Aero Engines.
2 Field of the invention
The invention relates to mechanical engineering field‘ This invention is
particularly for Aero-Engines and will also be applicable for Industrial
application.
3 Background of the Invention
Varieties of nuts are being used across various industry. Nuts/Lock Nuts
are meant for holding a bolt or a shaft tightly in its position. It’s necessary
that the nuts used on a machinery should not get loosed due to
vibrations/dynamic loading. Various features/arrangements are made on
nuts to avoid loosening and to create effective locking with mating
hardware. Some of the methods of locking the nut to avoid loosening are
spring washers, castle nuts, wire locking etc. The other way to avoid
loosening of nut is by using self-locking nuts. Self-Locking nuts have a
particular feature that will not allow it to loosen because of vibrations
during operation There are various types of self-locking nuts. Industrial
method of making self-locking nuts is by using a nylon strip at the end.
The other way of making self-Locking nut is by crimping the nut. This
crimping of a nut varies with size, material, design of nut and also amount
of crimping required. The present invention is a nut crimping tool for a lock
nut with lugs.
3.1 Prior Art
[U8005893291A]
Patent U8005893291A has been considered as prior art. In this patent the
inventor made a crimping tool for a lock nut used in trucks. Here the lock
has a ring type locking member with teeth extending outwardly from the
circumference. One of the teeth is bent over the flat surface of the nut to avoid rotation of the nut. To do this the tool has a puller and a bar‘ It is
understood that the crimping tool is used once the nut is tightened in its
place. And the nut is locked with a ring type member and not a self-locking
nut by itself.
The present invention is a crimping tool for a self-locking nut mostly used
in aero-engine applications. The tool is used for crimping the nut that
becomes a self-locking nut after crimping process There are no ring type
member that will lock the nut. The present invention has a cylindrical
shaped tool body and not a bar and puller type. The present invention is
completely different from the above invention.
[US$478564]
Patent US3478564 has been considered as prior art. In this patent, the
invention relates to improvements in crimping tools particularly of the type
which are used for the installation of fasteners And the invention is
specifically for a particular fastener. In this invention the nut is first
tightened on to the bolt and then the nut is crimped. The crimping is to
cause a portion of the counter bore of the collar to be forced into additional
locking grooves on the pin and to effect an elongation of the collar or nut
which places the bolt under a high residual tension.
The present invention is not to crimp the nut after installation. And this
invention is not for particular type of the fastener that the above invention
describes. This invention is for a completely different type of nut mostly
used in aero-engines. Here nut should be crimped individually to make a
self-locking nut. And this is not a fastener but a lock nut used on shafts.
[US3653802]
Patent US$653802 has been considered as prior art. The patent is a
motor driven tool with a rotatable socket. The motor driven tool drives the
nut on the threads and then crimps in its place. The tool have clamping.
jaws to crimp, and a jaw cup that actuates these clamping jaws. The figure
shown in the patent document is for a fastener which are mostly static
member. The tool is to crimp the cylindrical skirt that generates some
tensile stress on the bolt and avoid loosening with vibrations. The patent is
not for crimping the nut directly.
The present invention is a novel and simple to use tool for crimping a nut
individually and makes a self—locking nut. The present invention is not for a
fastener but a lock nut used on rotating shafts. This invention is completely
different from the above invention.
[JPH0641928U]
Patent JPH0641928U has been considered as prior art. The invention is to
deform a cylindrical portion at the end of the nut. This process is called
swaging of the nut. In this invention a nut with a thin cylindrical portion at
one end is used for swaging. The invention in this patent is a tool for
caulking a deformable cylindrical pinion from end of the nut into the
groove provided at ari end portion of the screw shaft.
The present invention is not a caulking tool. It's a crimping tool to deform a
specific design of the nut and to a specific amount of distortion. This is a
simple and easy to operate novel tool.
[CN101905272A]
Patent CN101905272A has been considered as prior art. The above
invention is regarding closing process of the lock nut used in aerospace
applications and also for industrial applications. There will be a radial
deformation on the nut and the amount of deformation on the nut has to be
checked after the process for each batch. There is a defined working
speed and holding time mentioned. The tool have pressure head that
needs to be changed based on the number of lugs on the nut or for an
elliptical closing. The invention talks about a machine with some touch
screen where you can set some speed, holding time and release for the
pressure head. And the iteration has to be followed for each batch after
ensuring the friction torque.
The presént invention here is for similar application. The tool invented is
completely different from what is mentioned in the above invention. In the
present invention the tool described is very simple, just a single piece and
no setting for operation, such that a semi-skilled operated can crimp the
nut. There are no pressure heads and changing of pressure heads. The
present invention is for a particular design of the nut and not for elliptical
crimping‘ The amount of crimp is already set in the tool for a given size.
The tool design will take care of the amount of crimp for a given size of the
nut and its material. The operator has to just crimp the nut, by using a
manual press or a hydraulic press‘ The operator work is minimized in this
invention‘ There is no measuring of the size at the end of the nut. Working
speed can be varied based on the operator and holding time after the
crimping is mentioned.
4 Brief Summary of the Invention
The invention of the tool and methodology of crimping are summarized
briefly here.
The invented tool is novel and simple.
There is no setting on the tool to use.
It is foolproof and a semi-skilled person can operate/use the tool.
The amount of crimp on the tool is controlled in the design and won’t
vary from nut to nut.
The amount of load to be applied on the nut to make self-locking is
fixed with the tool‘
One crimping tool for one size of the nut.
The crimping tools invented here are one for inward crimping of lugs on
lock nut with internal threads and the other is for outward crimping of the lugs-on threaded ring with external threads. The two tools are similar with
minor differences.
The crimping tool for inward crimping is a cylindrical part with a central
hole. It has a tapered hole portion at end. This taper hole is used for
inward crimping of lugs on internal threads lock nut. The taper angle of the
hole is arrived at with calculations and iterative experiments And the
dimensions of the taper portion aré 5150 based on the nut dimensions.
This taper portion will compress all the lugs together, when the lock nut is
pressed Over this.
'The crimping tool for outward crimping is a cylindrical pan with a central
hole. It has a tapered shaft portion at end. This taper shaft is used for
outward crimping of lugs on external threads lock nut/threaded ring. The
taper angle of the shaft is arrived at with calculations and iterative
experiments And the dimensions of the taper portion are also based on
the nut dimensions. This taper portion will expand all the lugs together.
when the threaded ring is pressed over this.
The sub-assembly shown will be placed over the taper portion and
pressed from the top using a hydraulic press or a hand press and will be
kept in that position for one minute.
After releasing the load, the lugs on the nut will have a residual
deformation with spring back, The compressing of lugs is called crimping
of the lock nut. The crimped lock nut needs some minimum application of
torque to tighten over the shaft. This feature will avoid lobsening of the
lock nut during operation.
This crimping tool is specific for a given nut size and features.
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: shows the lock nut [040] features in two different views. This is
the lock nut with internal threads. The number of lugs shown can vary with
the size of the nut. These type of nuts are used on rotating shafts.
Figure 2: shows the threaded ring (lock nut) [090] features in two different
views. This is the lock nut with external threads. The number of lugs
shown can vary with the size of the nut. These types of nuts are mostly
used on casings with internal threads.
Figure 3: The crimping tool [010] for inward crimping used on internal
threads lock nut [040] is shown here. This is the invention mentioned here
in the document.
Figure 4: The crimping tool [060] for outward crimping used on external
thread lock nut also called threaded ring [090] is shown here. This is the
invention mentioned here in the document.
Figure 5: This is the assembly of lock nut before crimping procedure The
items in this assembly are holding shaft.[030], aligning shaft [020] and the
lock nut [O40] positioned for crimping procedure. Bolts [050] holds the Figure 8: The Lock nut [090] positioned on the crimping tool [060] over the
taper portion [061] before proceeding for pressing.
6 Detail Description of the Invention
The following specification particularly describes the invention and the
manner in which it is to be performed.
Figure 1 § 2, shows the lock nuts that should be crimped to make self-
Locking nut. Figure-1 shows the external threads lock nut [040] and figure-
2 shows the internal threads lock nut [090] also called threaded ring.
These lock nuts have lugs on one side of the nut. These are made by
milling slots on one side of the lock nut. There is a groove made on these
lugs. This groove makes the lugs flexible at the groove. The groove
dimensions vary with the material of the lock nut. These lugs are
independent to each other and can be pressed individually to crimp the
nut. The thickness of the material at the groove and lug size determines
the amount of force required to crimp each lug and its spring back. This
will finally decides the locking torque for the self-locking nut.
Referring to Figure 3 & 4, the shown parts are crimping tools. This is the
invention that this patent claims for. Figure-3 shows the crimping tool for
Lock nut with internal threads and Figure-4 shows the crimping tool for
threaded ring. The purpose of this tool is to compress or expand the lugs
to certain extent. The compressed or expanded lugs will not attain the
original shape of the nut and will have some permanent set. This will be
the self-locking feature of the nut. To achieve this, the feature made on the
crimping tool is the taper portion. The depth or height of the taper portion
are decided based on nut dimensions, such that the distonion happens till
the lugs only. The angle of the taper is arrived based on the compression
or expansion required. Also this angle should be arrived iteratively based
on groove size, material of the lock nut and lug dimensions. The central
assembly together.
Figure 6: This is the assembly of threaded ring before crimping procedure.
The items in this assembly are holding shaft [070], aligning shaft [080] and
the lock nut [090] positioned for crimping procedure. Bolts [050] holds the
assembly together:
Figure 7: The Lock nut [O40] positioned on the crimping tool [010] over the
taper pinion [011] before proceeding for pressing.
Figure 8: The Lock nut [090] positioned on the crimping tool [060] over the
taper portion [061] before proceeding for pressing.
6 Detail Description of the Invention
The following specification particularly describes the invention and the
manner in which it is to be performed.
Figure 1 § 2, shows the lock nuts that should be crimped to make self-
Locking nut. Figure-1 shows the external threads lock nut [040] and figure-
2 shows the internal threads lock nut [090] also called threaded ring.
These lock nuts have lugs on one side of the nut. These are made by
milling slots on one side of the lock nut. There is a groove made on these
lugs. This groove makes the lugs flexible at the groove. The groove
dimensions vary with the material of the lock nut. These lugs are
independent to each other and can be pressed individually to crimp the
nut. The thickness of the material at the groove and lug size determines
the amount of force required to crimp each lug and its spring back. This
will finally decides the locking torque for the self-locking nut.
Referring to Figure 3 & 4, the shown parts are crimping tools. This is the
invention that this patent claims for. Figure-3 shows the crimping tool for
Lock nut with internal threads and Figure-4 shows the crimping tool for
threaded ring. The purpose of this tool is to compress or expand the lugs
to certain extent. The compressed or expanded lugs will not attain the
original shape of the nut and will have some permanent set. This will be
the self-locking feature of the nut. To achieve this, the feature made on the
crimping tool is the taper portion. The depth or height of the taper portion
are decided based on nut dimensions, such that the distonion happens till
the lugs only. The angle of the taper is arrived based on the compression
or expansion required. Also this angle should be arrived iteratively based
on groove size, material of the lock nut and lug dimensions. The central
hole on the crimping tool witH guide the nut assembly while pressing
ensuring the smoother operation.
Referring to Figure 5, the assembly before going ahead for crimping of
the lock nut is shown. The lock nut should be hold above the groove only
and pressed with alignment. In figure 5, nut holding shaft [030] have
external threads and the shaft portion for alignment into the crimping tool.
Nut locating shaft [020] will place the nut at desired position. Nut holding
shaft [030] and nut locating shaft [020] are assembled as is figure 5 and
tightened with bolts [050]. The lock nut will be hand tightened on the
projected threaded portion on nut holding tool [030]. Nut locating shaft
[020] will stop the nut at the desired position. Now the assembly is ready
for pressing.
Referring to Figure 6, the assembly before going ahead for crimping of
the threaded ring is shown. The threaded should be hold above the groove
only and pressed with alignment. In figure 6, nut holding shaft [070] have
internal threads. Nut locating shaft [080] will place the nut at desired
position and the shaft portion for alignment into the crimping tool. Nut
holding shaft [070] and nut locating shaft [080] are assembled as is figure
5 and tightened with bolts [050]. The lock nut will be hand tightened on the
projected threaded portion on nut holding tool [070]. Nut locating shaft
[020] wiII stop the nut at the desired position. Now the assembly is ready
for pressing.
Referring to Figure 7 & 8, the figure shows the final assembly before
crimping the nut. In figure 7 the assembly of lock nut as shown in figure 5
is placed over crimping tool [010]. The nut will touch taper surface at
desired location. Some lubricant like oil or white grease shall be applied on
the taper surface and locating shaft before pressing. The pressing can be
done using a hydraulic press or a hand pressing machine. The pressing
should be done till the nut touch the bottom and should be held in that
position for one minute‘ After a minute the pressure can be removed. The
lock nut sub assembly can be removed by hand. The locknut [040] shall
be removed from nut holding tool [030]. This will be a self-locking nut and
can be used in the assembly. And the procedure is same for threaded ring
5 [090] as shown in figure 8.
For the given lock nut design as shown in figure 1 & 2, the crimping tool
was invented. Taper portion is the crucial part that determines the amount
of crimping and the locking torque of the nut. The initial estimation of the
taper angle is crucial. Later on the optimization of taper to achieve the
10 required crimping or required locking torque was done iteratively. The
amount of crimping vary with material of lock nut, groove dimensions and
the required locking torque.
It was ensured that the crimping tool material harder than the lock nut else
crimping tool material will wear out damaging the taper portion. Also
sufficient lubrication should be provided on the taper to avoid damage of
material or surface.
We Claim,
A Nut Crimping tool [010] to inward crimp the lock nut [040] with internal
threads [043], lugs [042] and a groove [041] and another Nui Crimping
tool [060] to outward crimp the threaded ring [090] with external threads
[093], lugs [092] and a groove [091] comprising:
a Nut Crimping tool [010] with a taper hole [011] for inward crimping and
a central hole [012] for alignment of locknut [040] with the taper hole
[011;
a Nut Crimping tool [060] with a taper shaft [061] for outward crimping
and a central hole [062] for alignment of Threaded ring [090] with the
taper shaft [061]
a Nut holding shaft [030] with external threads [031] for holding lock nut
[040] and shaft [032] for alignment during crimping process;
a Nut holding shaft [070] with internal threads [071] for holding threaded
ring [090];
a Nut alignment shaft [020] to ensure that the locknut [040] is held only
till the groove [041] or less than that; and
3 Nut alignment shaft [080] to ensure that the threaded ring [090] is held
only till the groove [091] or less than that and shaft [081] for alignment
of the threaded ring [090] with the nut crimping tool [060].
Nut crimping tool [010] as claimed in Claim 1; a taper hole [011] of 9° to
15° for inward crimping of said lugs [042] on said lock nut [040).
Nut crimping tool [060] as claimed. in Claim 1; a taper shaft [061] of 12°
to 18° for outward crimping of said lugs [092] on said threaded ring [090]
and a center hole [062] for alignment.