FIELD OF INVENTION
The present invention relates to a device to inspect the aerofoil
profile width of fan blade. The present invention is particularly
provided to control the width of profile on leading edge and trailing
edge of fan blade at different section along the length by measuring
in single setting, wherein the fan blades are used in the utility and
industrial boilers.
BACKGROUND OF THE INVENTION
Blades are used in the impeller of fans. Fan is a type of turbo
machinery used for energy transfer. It can be defined as a rotating
machine with a bladed impeller which maintains a continuous flow
of air or gas. It is continuous because the flow at entry and exit
and also through the impeller is steady. Here the energy transfer
takes place from the machine to the flowing fluid.
The fan is axial reaction type- major portion of static pressure is
developed in the impeller. The angle of incidence of the blades can
be adjusted during operation. The pressure volume characteristic
curves of the fan may be changed in a long range without
considerable change in efficiency. The fan can thus be easily
adapted to changing operating conditions.
The fan consists of the following main components:-
> Impeller with blades and adjusting mechanism.

> Shaft with bearing assembly with thermometers
> Suction box, impeller housing and diffuser.
> Spacer coupling
> Forced oil lubrication system
Impeller are made from fine grain steel and are machined precisely
to accommodate a set of replaceable aerofoil blades on blade
shafts. The blade shafts are placed in combined radial and axial
anti-friction bearings which are sealed to the outside. The
centrifugal and adjusting forces of the blade are taken up by the
blade bearings.
Aerofoil blades are rotated about their axis to control the air flow
rate. In fully open position maximum flow of air is allowed and in
fully closed position minimum or zero air flow is allowed through
blades. In fully closed position minimum blade to blade gap should
be maintained (as shown in fig. 1). Any variation in width leads to
either interference of blades or more gap between blades. To avoid
this problem, profile width of blade is required to be controlled.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a device to
inspect the aerofoil profile width of fan blade after machining or
grinding the width.

Another object of the present invention is to provide a device to
inspect the aerofoil profile width of fan blade which is simple in
construction and easy to use for checking the profile width.
Further object of the present invention is to provide a device to
inspect the aerofoil profile width of fan blade which is efficient.
Still another object of the invention is to reduce the inspection time
for checking the profile width.
SUMMARY OF THE INVENTION
Accordingly, the present invention is provided with a base plate on
which blade is placed for inspection. Two side plates are formed to
the shape of aerofoil profile on leading edge side and trailing edge
side, maintaining profile width from the centre line. Blade is placed
on the base plate and width is measured by checking the gap
between blade profile and formed plates in the device with the help
of feeler gauge.
STATEMENT OF INVENTION
According to this invention, there is provided a device to inspect
aerofoil profile width of fan blade comprising of a base plate
mounted with formed plate leading edge side and formed plate
trailing edge side fixed to a plurality of straight plates.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Further objects and advantages of this invention will be more
apparent from the ensuing description when read in conjunction
with the accompanying drawings and wherein:
Fig. 1 shows : impeller with blades in fully closed position of
aerofoil profile blades.
Fig. 2 shows: a device to inspect the aerofoil profile width of fan
blade.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE
TO THE ACCOMPANYING DRAWINGS;
The present invention discloses a device to inspect the aerofoil
profile width of fan blade. The device comprising of a base plate
(01) with locating diameter for placing the blade mounted with
formed plate (02) leading edge side and formed plate (03) trailing
edge side in vertical direction. Both formed plates are fixed to the
straight plates (04) by screws (05) and nuts (06). The two straight
plates (04) are welded to the base plate (01).
Fan blade profile width is required to be checked at each profile
after width correction. The known method of checking each profile
width is a tedious process which is as follows-
1. Marking the section height as per the drawing on the
blade with the help of vernier height gauge (20mins).

2. Mounting the blade in the check (10 mins).
3. Setting the profile tangent at market height to 90 deg.
4. Measuring the width at this position for a particular
section which involves
i) Finding boss center.
ii) Measuring the leading edge width from the boss
center,
iii) Measuring the trailing edge width from the leading
edge (15 mins for measuring each section)
5. Repeating the steps from 3 to 4 for all sections (90 mins).
Total inspection time for single blade width inspection: 120 mins.
The method of checking each profile width using the present
invention is simple and easy, which is as follows:-
1. Master blade is made ready to the maximum size of blade
width.
2. Formed plates in the device checked by master blade and
deviations found in profile width are corrected by
adjusting the screws.
3. Width of formed plates in device for trailing edge and
leading edge side are inspected and calibrated.
4. Blade is placed on the calibrated device and the gap
between formed plates in device and aerofoil blade profile
is measured by using feeler gauges.

5. Blade width is calculated by subtracting the gap between
formed plates and blade from the known width of formed
plates.
Advantageous features
1. It ensures the blade width within tolerance limits.
2. It reduces the cycle time of width checking drastically
from 120mins to 10 mins.
3. It avoids the old method of tedious checking making the
process simpler.
4. The device can be corrected very easily with the help of
fasteners whenever deviations found in the device.
It is to be noted that the present invention is susceptible to
modifications, adaptations and changes by those skilled in the art.
Such variant embodiments employing the concepts and features of
this invention are intended to be within the scope of the present
invention, which is further set forth under the following claims:-

WE CLAIM;
1. A device to inspect aerofoil profile width of fan blade
comprising of a base plate mounted with formed plate
leading edge side and formed plate trailing edge side fixed
to a plurality of straight plates.
2. A device as claimed in claim 1, wherein the straight plates
are welded to said base plate.
3. A device as claimed in claim 1 or 2, wherein the device
ensures the blade width within tolerance limits.
4. A device as claimed in any of the preceding claims,
wherein blade is positioned on the base plate for
inspection.
5. A device to inspect aerofoil profile width of fan blade
substantially as herein described with reference to the
accompanying drawings.

This invention relates to a device to inspect aerofoil profile width of
fan blade comprising of a base plate mounted with formed plate
leading edge side and formed plate trailing edge side fixed to a
plurality of straight plates.