FIELD OF INVENTION
The present invention relates to a system for clamping all rectangular cross-section blanks
in 3-spindle 5-axis machines for machining steam turbine blades.
In particular it relates to a system for clamping all sizes of rectangular blanks, including
blanks of lower cross-sections, which otherwise could not be clamped in the existing
system, for machining purpose.
BACKGROUND OF THE INVENTION
3-spindle, 5-axis machines are used for machining of steam turbine blades from a
rectangular blank to finished blade. All the blanks are put in the part changer of the
machines in series each machine taking a set of 3 blanks at a time to get them machined
and then these are taken out of the machine and put on finishing positions in the part
changer area on completion, a next set of 3 blanks are put for machining and the cycle
continues.
In some machines the clamping system in the part changer are basically designed for
clamping bigger size blanks and in some other machines they are designed for clamping
smaller size blanks. In the machines meant for larger cross section of blanks, the clamping
system in the part changer will not be able to clamp smaller cross-section of blanks.
Thus, in an emergency when all the machines are required for machining smaller cross-
section of blanks, machines basically meant for machining bigger size blanks, cannot be
used.
There is therefore, a need to modify the clamping system in the machines meant for
machining blades of bigger cross-section so that any cross-section of blank can be clamped
in these machines.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide a modified clamping system for
clamping all rectangular cross-section blanks for machining steam turbine blades in 3-
spindle, 5-axsis machines.
Another object of the present invention is to provide 3-spindle, 5-axis machine for turbine
blade machining with the modified clamping arrangement.
In a preferred embodiment, the present invention provides a system for clamping all
rectangular cross-section blanks in a 3-spindle, 5-axis machine for machining steam turbine
blades, said system comprising a piston-cylinder assembly having a spring loaded
arrangement with a jaw for keeping a blank to be machined pushed forward so as to keep
the blank in vertically straight position; characterized in that said jaw is provided with a
threaded hole with an extension bolt fitted thereto, thereby extending the length of the
piston to accommodate clamping blanks of all cross-section.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention can now be explained with reference to the accompanying drawings where
Figure 1 shows in schematic form the existing clamping system
of part changer of a 3-spindle, 5-axis machine.
Figure 2 shows the modified clamping system of the present invention.
DETAILED DESCRIPTION
As shown in Figure 1 a piston and cylinder assembly is provided with a piston 5 moving
forward and backward in a cylinder 4. The piston 5 is supported by a spring loaded
arrangement 3 having a jaw 7 which always keeps a machining blank 1 pushed in a
forward direction so as to keep the blank 1 vertically straight against walls 2.
The purpose of keeping the blank straight is to ensure that the blank is kept in a pre-
defined place so that when the arm of part changer comes to pick up the blank it does not
collide with the blank, when it is wrongly placed.
From the cross-section of blank fed by the operator in the machine the machine
understands that the defined width and thickness of the blank start from the support walls
2 to defined width and thickness and the machine provides signal to its arms to pick up the
blank of pre-defined cross-section. The gap between machine arms and blank width are
approximately 2 to 4 mm both sides. That is why a little deviation in the placement of
blank will result in collision of arms with the blank. Hence the blank cannot be put in the
part changer without giving support from the spring loaded piston.
In machines where the clamping systems in the part changer of machines are basically
designed for clamping bigger size blanks of cross-section 50 x 36 to 90 x 50 the clamping
system in the part changer is not able to clamp the smaller cross-section of blanks from
cross-section 40 x 20 to 50 x 36.
In order to accommodate blanks with cross-section from 40 x 20 to 50 x 36, it is required
either to move the piston assembly closer to the smaller blank or move only the piston
closer to blank but in both the cases the bigger cross-section blanks will not get clamped as
distance between support walls 2 and clamping jaw 7 gets reduced. The present invention
provides a solution to this problem of clamping smaller cross-section blanks without
disturbing the piston and cylinder assembly. An internal threaded hole 8 is made in the
jaw 7 from front side and a bolt 8 with head is fixed on that jaw 7 to extend the length of
piston so that blanks with smaller cross-section could be clamped as shown in Figure 2.
With this new arrangement of the present invention blanks of any cross-section from 40 x
20 to 90 x 50 can be clamped in any of 5-axis, 3-spindle machines.
WE CLAIM
1. A system for clamping all rectangular cross-section blanks in a 3-spindle, 5-axis
machine for machining steam turbine blades, said system comprising a piston-
cylinder assembly having a spring loaded arrangement with a jaw for keeping a
blank to be machined pushed forward so as to keep the blank in vertically straight
position;
characterized in that said jaw is provided with a threaded hole with an extension
bolt fitted thereto,
thereby extending the length of the piston to accommodate clamping blanks of all
cross-section.
2. The system as claimed in claim 1, wherein said system is capable of accommodating
blanks of any cross-section from 40 mm x 20 mm to 90 mm x 50 mm.
3. A 3-spindle, 5-axis machine for machining steam turbine blades fitted with a blank
clamping system as claimed in the preceding claims.
4. A system for clamping all rectangular cross-section blanks in a 3-spindle, 5-axis
machine for machining steam turbine blades, substantially as herein described and
illustrated in the figures of the accompanying drawings.

The main object of the present invention is to provide a modified clamping system for
clamping all rectangular cross-section blanks for machining steam turbine blades in 3-
spindle, 5-axsis machines.
Another object of the present invention is to provide 3-spindle, 5-axis machine for turbine
blade machining with the modified clamping arrangement.
In a preferred embodiment, the present invention provides a system for clamping all
rectangular cross-section blanks in a 3-spindle, 5-axis machine for machining steam turbine
blades, said system comprising a piston-cylinder assembly having a spring loaded
arrangement with a jaw for keeping a blank to be machined pushed forward so as to keep
the blank in vertically straight position; characterized in that said jaw is provided with a
threaded hole with an extension bolt fitted thereto, thereby extending the length of the
piston to accommodate clamping blanks of all cross-section.