FIELD OF THE INVENTION
The present invention relates to a device for checking inside contour of yoke
engaged in servomotor of turbine.
BACKGROUND OF THE INVENTION
Yoke, one of main component of servomotor is a casting, its turning is carried
out lathe machine followed by detail machining on horizontal boring machine.
Subsequently assembly work is being carried out. One lever assembly is mounted
on servomotor piston rod is assembled with yoke. Colour matching of lever
assembly is carried out with yoke.
During assembly it was observed that lever surface is not matching with
matching surface of yoke. Resulting in gap upto 5 mm either extending towards
centre of the piston rod or away from centre.
Assembled yoke with piston rod is sent to horizontal boring machine for
rectification. Yokewall is machined till the lever surface found perfectly matching
with yoke surface. This lead mainly three types of non-confirmities threaded
holes M16/M20 in yoke wall. It also required to be enlarged to make its axis
perpendicular to the yoke surface. Support holes are also enlarged as per the
new hole on yoke.
The above non-confirmities lead to engagement of horizontal boring machine
repeatedly causing delay to other components waiting for machining
engagement of crane and material handling staff.
Rework during assembly leads to delay in completing assembly of complete stop
and control valve for despatch.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a fixture for
checking inside contour of yoke engaged in servomotor of turbine which
eliminates the disadvantages of the present state of work.
Another object of the present invention is to propose a fixture for checking inside
contour of yoke engaged in servomotor of turbine which increase the production.
A further object of the present invention is to propose a fixture for checking
inside contour of yoke engaged in servomotor of turbine which reduces the
salvage time of yoke.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig.1 - shows a schematic drawing of checking device
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
To overcome the recurring problem, the inventor develops a checking device
which can be used for all as per yoke of rating of valve.
A detailed study was carried out on yoke drawings in all applicable servomotors.
As the turbine made on modular concepts, the basic feature of yoke are found
same with some variation in dimensions. Taking into account dimensions of all
the yoke, a universal bush (1) was made by machining in a lathe from steel stock
having diameter at steps of 70, 80, 90, 180, 230, 280 and 260 with a finished
hole of diameter 40 at the centre.
A spindle (2) of diameter 40-0.02 is manufactured by a steel stock by machining
in a lathe for the purpose of fitting to the central hole in stepped bush. The
spindle has a radial hole (3) having diameter 22 + 0.02 exactly passing through
the centre line at the open end.
A sliding lever (4) manufactured from tool shank for fitting into the radial hole of
the spindle. This sliding lever will serve a purpose of a dummy lever for matching
contact surface with the yoke.
A rectangular clamp (5) of size (70 mm x 80 mm) is manufactured by making a
vertical central hole (6) of 40 mm diameter through which one end of the spindle
(2) passed through, by a drilling. A vertical gap (7) is made from one open side
upto the periphery of the central hole by cutting with hacksaw. One horizontal
drill and tap hole (8) is made from one side of the rectangular clamp which is
perpendicular to the gap and passes through the gap to insert a M18 bolt (8) for
fastening tightly with spindle (2).
The checking device is made by assembling all the parts, first of all the first end
of the spindle (2) is inserted in the central hole of the stepped bush (1) and is
fastened with a rectangular clamp (5) by bolting (9). The sliding lever (4) is
inserted into the hole (3) of the second end of the spindle (2).
WE CLAIM
1. A device for checking inside contour of yoke engaged in servomotor of
turbine comprising an assembly of:
- one combined multi-stepped bush (11) having diameter 70 to 260
mm;
- one spindle (2) of diameter 40 + 0.02 mm having a radial drill hole
diameter 22 + 0.02 mm;
- one sliding lever (4) having diameter of 20 + 0.02 and of length
400 mm;
- one rectangular clamp;
characterised in that said device is placed inside the yoke to check the
machining surface of yoke and also check the alignment of piston rod.

The present invention relates to a device for checking inside contour of yoke
engaged in servomotor of turbine comprising an assembly of one combined
multi-stepped bush (11) having diameter 70 to 260 mm and one spindle (2) of
diameter 40 + 0.02 mm having a radial drill hole diameter 22 + 0.02 mm and
one sliding lever (4) having diameter of 20 + 0.02 and of length 400 mm and
one rectangular clamp characterised in that said device is placed inside the yoke
to check the machining surface of yoke and also check the alignment of piston rod.