1. Title:
A method of blade locking with disc by deformable lock plate.
2. Field of Invention:
This invention pertains to mechanical engineering field in general and in particular to aero engine blade locking.
3. Background of the invention
In turbomachinery, blades with dove tail root and the dove tail slot on the disc are assembled. Under the centrifugal load on blade and disc during rotation, because of dove tail configuration on disc and blades they are naturally locked. But compressor and turbine of turbo machinery operate under differential gas dynamic pressure. This leads to axial movement of the blades relative to disc. Hence, an arrangement is provided to arrest such axial movement of the blade with respect the disc and they are provided with pin, ring or other arrangement of tab locks. US 5622475 Patent discloses a locking mechanism in a turbine rotor assembly includes a rotor disk, rotor blades joined thereto, and a blade retention plate for axially retaining the blades on the disk. The disk includes an outer rim, an inner hub, and an annular web extending there between. An axial extension extends from the web and is spaced radially below a corner of the rim. The blades have dovetails axially disposed in respective dovetail slots in the disk rim. The retention plate includes an outer rim which abuts the disk rim and blade dovetails, an inner hub, and a web extending there between. The plate hub has an outer rabbet disposed in abutting contact with the rim corner, and an inner rabbet radially adjoining the axial extension for maintaining abutting contact therewith upon differential radial contraction between the retention plate and the disk which separates the outer rabbet from the rim corner. In one embodiment, the assembly further includes a locking ring disposed between the retention plate and the axial extension for axially trapping the plate adjacent to the disk rim. EP1650406 B1 also discloses A locking assembly for a rotor stage of a gas turbine engine, the rotor stage comprising an annular array of radially extending blades secured to a rotor disc via

an attachment and an annular retaining plate capable of preventing axial movement of the blades, the retaining plate is secured to an axial face of the disc via a bayonet arrangement. The retaining plate lock arrests all the blades in its positions. So independent and individual blade dismantling is not possible due to a common lock plate arrangement of locking.
During operation of the turbomachinery, if any sort of Foreign Object Damage (FOD)/ Internal Object Damage (IOD) happens, blades are replaced and new blades are inserted into the disc slots and there after the assembly is locked. In these above type of configurations of blade locking arrangement, individual replacement of the blade takes longer duration for replacement which even leads to partial to complete disassembly of the rotors and disc from the machinery. So the turnaround time for replacement is high which reduces high maintenance man hrs and reduced availability of the turbomachinery. Generally the operating bases do not have the required facility and expertise to handle the scale of dismantling and assembly operations, so the turbomachinery often visits the overhauling company there by further reducing the downtime of the machinery and other associated costs like transportation and insurance costs. 4. Brief Description of Invention:
This invention discloses a method of blade locking during rotor assembly with blade (101) and
the disc (102) of turbo machinery with deformable blade lock (103, 104). It provides a locking
arrangement of the rotor assembly which avoid axial movement of the blade (101) relative to
the disc (102) in the axial direction due to the differential gas dynamic force of gas pressure. In
the axial flow compressor downstream pressure is higher than the upstream pressure. Whereas
in turbine upstream pressure are higher than the downstream pressure. The deferential
pressure acts on blade feather, resulting it to move axially from high pressure to low pressure
direction during turbomachinery operation. The present invention relates to a deformable tab
lock (201, 202, 203) positioned in the axial slots of the blade (303, 304) and are subsequently
bent left and right ward direction and firmly attached to the disc (401, 404). The lab locks (201,

203) which are positioned in the blade slots (303, 304) are prevented from radial movement with material support of the blade slot and axial movement by bent of the tab (201, 203) on the lock with the disc face (401, 404). In this type of configuration, it is possible to lock the individual blades (101) with the disc (102) with bent tab locks (201, 203). The process is quick and can be done at operating bases which will increase the availability of the turbo machinery and decrease the turnaround time of the machinery. Also the frequent requirement to send the turbomachinery to overhauling agencies; for such time of blade replacement works are reduced saving costs.
5. Brief Description of Drawing:
Fig.100: Exploded view of blade locking on disc of turbo machineries with blade locks
101-Blade,
102-Disc,
103,104- Blade locks
Fig. 200. Lock plate
201, 203-Tab portion of the lock plate
201 - Stem part of the lock plate
Fig.300: Locking slots on blade
301- Blade feather
302 -dove tail root of the blade
303, 304 - The dove tail root has two slots running axially along the dove tail root
Fig. 400: Locking arrangement with lock plates on turbo machinery disc
401- Face of the disc on upstream

402- Tab of lock plate
403- Tab Lock plate
404- Face of the disc on downstream 405-Tab of Lock plate
406- Tab of lock plate
6. Detail Description of Invention:
In Fig.100. 101 is a blade, 102 is the disc of the turbomachinery, 103 and 104 are deformable
blade locks. On disc (102) several dovetail slots are machined to accommodate blades (101) to
make a rotor.
In Fig. 200. 201 and 203 are tab portions of the lock plate. 201 is stem part of the lock plate.
The tab 201 and 203 are bigger in height than the blade slot. The tab 201 and 203 shall not
enter the slot of the blade axially. The blade lock thickness is slightly thinner than the blade slot
to easy sliding axially.
In fig.300. The blade feather is designated as 301, 302 is the dove tail root of the blade. The
dove tail root has two slots 303 and 304 running axially along the dove tail root. The slots 303
and 304 shall accommodate two blade locks. The dove tail root slide axially and assembled on
disc slot.
In Fig. 400a, the blades are assembled with lock plates. The tab 402 and 403 of the lock plate is
bent and is pressed on the face of the disc rim 401. The tab 402 is bent towards left side and
tab 403 is bent towards right side.
In Fig.400b, The tab 404 and 405 of the lock plate is bent and is pressed on the face of the disc
rim 406. The tab 404 is bent towards left side and tab 405 is bent towards right side.

The invention discloses a blade locking method for compressor disc (102) and blade locking in axial direction. However this invention will be applicable for turbine or similar kind of turbomachinery's application also. The compressor disc (102) is basically constituents of three portions i.e hub, web and rim as shown in Fig.100. On the rim of the disc, axial slots are provided for inserting the blade (101) root. For the present invention the disc (102) is having several slots with dove tail shape and the blades are also having dovetail roots with two axial slots (303, 304) running through the entire length of the blade (101) root. The locking plate (103 or 104) is a thin plate having two tabs (201, 203) at the end of the plate. The thickness of the plate is slightly less than the width of the slot of the blade root. The height of the plate lock (202) at mid portion is slightly less than the height of the axial slot on the blade. The length and height tab (201 &203) portion is sufficiently enough for locking the blade with the disc when the tab is bent and pressed to the face of the disc (401, 404).
Compressor is rotated by some kind of prime mover say turbine or other apparatus. The compressor usually produces high pressure than the atmosphere. The flow of air or gas takes place from upstream to downstream direction. In that process of rotation the blade (101) and disc (102) are subjected to centrifugal force. When the blade feather is additionally experiencing axial force due to differential gas pressure, the blade (101) will try to move from high pressure region to low pressure region i.e from downstream to upstream direction. There are two blade slots (303, 304) which are marked for left slot and right slot. Two blade locks (201, 203) is inserted into the blade slots (303, 304) vertically upward direction initially. Then the upstream lock tab (402) is bent leftward of left blade lock. Similarly lock tab (403) is bent towards right of the right blade lock. The blade (101) with two blade lock tabs (103, 104)

are inserted into dove tail slot of the disc axially and moved further axially till the blade with locks cover the full length of the dove tail slot on the disc (102). The lock tabs (405, 406) at the downstream end is bent and pressed on the face of the disc. The left side locking plate tab (406) is bent towards left direction. The right side locking plate tab (405) is bent towards right direction. The embodiment of the invention shall prevent the blade to move axially from either direction of downstream to upstream direction vice versa. The embodiment of the invention shall prevent the blade to move axially from either direction of downstream to upstream direction vice versa. This arrangement will also have less weight compared to other locking arrangements involving rings. As the blades (101) are individually locked to the disc (102), this embodiment will have less time for assembly and disassembly of the blades (101) onto and from the disc (102). This will reduce the turnaround time of the turbomachinery in case of any change of blades. As the activities involved in change of the blade (101) will be less, this activities can be undertaken at operating bases there by reducing costs of transportation and insurance and increase availability of the machinery for operation.

We claim:
1. A method of blade (101) locking with disc (102) by deformable blade lock plate (103,104) in a
turbomachinery characterized in that;
-It consists of a thin blade lock (202) which lock the blades (101) onto the discs (102) -by inserting the blade lock (202) inside the blade slots (303, 304) -by bending the tab towards left (402,406) and right (403,405) -on the disc surface (401, 404).
2. The method as claimed in 1 can be used to assemble and disassemble the blades (101) on to
the discs (102) individually without any ring arrangement.
3. The method as claimed in 1 shall have less weight compared to others type of locking arrangement.
4. The method as claimed in 1 can be implemented at operating bases of the turbo machinery and will eliminate visit of the machinery to overhauling agency there by reducing downtimes and saving costs.