FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
PROVISIONAL / COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION
SPECIAL COMBINATION TOOL
2. APPLICANT
(a) NAME : Larsen and Toubro Ltd.
(b) NATIONALITY.: Indian Company, registered under the provisions of the
Companies Act, 1956
(c) ADDRESS : L&T House, Ballard Estate, Maharashtra State, India.
3. PREAMBLE TO THE DESCRIPTION

PROVISIONAL
The following specification describes the invention,.

COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

4. DESCRIPTION (Description starts from page 2)
5. CLAIMS: 5Nos
6. DATE AND SIGNATURE: Given at the end of last page of specification.
7. ABSTRACT OF THE INVENTION: On separate page

Title of the invention: - SPECIAL COMBINATION TOOL
Field of invention: - This invention relates to machining the ends of the tubes of the heat exchanger after welding the tubes on the tube sheet.
Prior Art: -
The prior art is described with help of following figures.
Fig. 5 shows the operation of internal boring.
Fig. 6 shows the operation of chamfering.
Fig. 7 shows the operation of external turning.
Fig. 8 shows the operation of external chamfering
With reference to above figures, tube sheet 28 is provided with plurality of holes 31 in to which the tubes 29 are inserted. The part of the tube, which actually forms the heat-exchanging surface, is considerably longer and projects on the left side of the tube sheet 28 shown in the figure. The smaller lengths of the tubes 29 extend on the right side of the tube sheet 28, which is the side from which the heat exchanging fluid enters the tubes 29. The tubes 29 are welded to the tube sheet 28 by a leak proof weld 30. The welding operation is done before the ends of tubes 29 are machined to avoid any distortion in the machined portion due to thermal stresses caused by the welding operation.
The tube sheet welded with the tubes is then mounted on the floor type boring machine table with the tube ends to be machined facing the spindle. The spindle is aligned with one of the tubes.
The machining operation is then done in following sequence. 1) inside boring as shown in Fig 5 with inside boring tool 51,2) inside chamfering as shown in Fig 6 with inside chamfering tool 61, 3) outside turning as shown in Fig 7 with out side turning tool 71, and 4) out side chamfering as shown In fig 8 with out side chamfering tool 81.
During all the above operations the respective tool is mounted on the spindle of the machine, then the tool is set

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to achieve the correct dimension on the tube after
machining and then the machining operation is done. After
every operation the tool is removed and tool for the next
operation is set on the machine. In this way all the four
operations are completed on a tube in sequence. After
finishing one tube, next tube is aligned with the spindle and
the process is repeated till all the tubes are finish
machined.
Deficiencies and drawbacks of the prior art.
As the machining is done in four passes and four different
settings, requires four tool changes, the machining time is
very high.
There is risk of error in relocating the tool, which can cause
disturbance in pre set radius on tool and deviation in the
dimension produced.
Summery of present invention.
The objective of the present invention is to overcome the
above drawbacks by providing a single combination of three
tools in to a special combination tool, which can perform all
four operations in a single setting and single pass of the
machine spindle. It is found that this combination tool can
reduce the machining time up to 60% compared to the
process used in the prior art.
The statement of invention:
A special combination tool comprising, spindle 2, tool main body 4, the tool main body 4 having face 5 perpendicular to the axis of the spindle 2, three blocks 6,7 and 8 fitted on the face 5, block 6 and 7 being spaced at 180 deg angle with respect to each other while block 8 being fitted spaced at 90 degrees with reference to the two blocks 6 and 7, two

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precision holes 9 and 10 being provided in the blocks 7 and 6 respectively, the axis of the said bores being oriented in perpendicular direction with reference to the axis of the spindle 2, two micro bore cartridges 11 and 12 being provided in holes 9 and 10 respectively for precision adjustment of the internal boring and chamfering tool 19 and external turning tool 20 in radial direction, the internal boring and chamfering tool 19 and external turning tool 20 being mounted on inner ends of micro bore cartridges 11 and 12 respectively, screw 13 and washer 14 being provided for tightening the micro bore cartridge 11 in position after setting while screw 15 and washer 16 being provided for tightening the micro bore cartridge 13 after setting, at inside end the micro bore cartridges 11 and 12 are being provided with fine threads 23 and 24 on which setting nuts 17 and 18 are being provided respectively, on the out side ends of the , of the micro bore cartridges 11 and 12 two integral lugs 25 being provided on each cartridge, the lugs 25 being slide fit in the slots 26 being provided in holes 9 and 10; out side chamfering tool 27 being mounted on block 8.
The invention is now described in detail with reference to the following figures.
Fig. 1 Shows the front view of the invention, special combination tool.
Fig. 2 shows the view "V" with reference to fig. 1 and shows the details and mounting of the out side-chamfering tool. Fig. 3 shows the section "X-X" with reference to fig 1. Fig. 4 shows the section "Y-Y" with reference to fig 3. With reference to above figures, the special combination tool 1 comprises of, a parallel shank 2 which can be mounted on the machine spindle 3. Main tool body 4 is fixed to the shank 2 in such a way that the front face 5 of the main tool body is at right angles to the axis of the

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shank 2. Three blocks 6, 7, 8 are mounted on the face 5 for mounting three different tools. The blocks 6 and 7 are
positioned at 180-degree angle with respect to each other,
while block 8 is positioned at 90 degrees with respect to
blocks 6 and 7. Blocks 6 and 7 are provided with a precision parallel bores 9 and 10 radially positioned with reference to
the spindle axis. Micro bore cartridges 11 and 12 are fitted
in the bores 9 and 10 respectively. The micro bore
cartridges are provided with fine threads 23 and 24 at inner
end and two lugs 25 at the outer end as shown. Two
parallel slots 26 are provided in each of the blocks 6 and 7.
The lugs 25 are slide fit in the slots 26 thus allowing only
axial movement of the micro bore cartridges 11 and 12 in
holes 9 and 10, and the rotary movement being arrested. A
set of screw 13 and washer 14 is provided to tighten the
micro bore cartridge 11 in position after the setting while
similar set of screw 15 and washer 16 is provided to tighten
the micro bore cartridge 12 for tightening. Two setting nuts
17 and 18 are provided on the micro bore cartridges 11 and
12, (on their threaded parts 23 and 24) respectively to
facilitate accurate setting of the tools viz. inside boring and chamfering tool 19 and out side turning tool 20 fitted at the
inner end of the micro bore cartridges 11 and 12
respectively. The cutting edge of the inside boring tool is
set at an angle of 5 degrees with reference to the
shank/spindle axis so that the 5 degree chamfer at the
inside end of the bore is machined by the inside boring tool
at end of its forward stroke. The bore gets machined by the
outer end of the carbide cutting tool tip, fixed at the end of

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this tool. Thus inside boring and chamfering is done by a
single tool. The nuts 17 and 18 are provided with a
hexagonal step 21 to facilitate rotation of the said nuts with
help of a tool, like spanner. The setting nuts 17 and 18 are provided with graduation marks 22 on the step adjacent to
the faces of the blocks 6 and 7 and the said blocks being provided with fixed marks (not shown in the drawing) one
each on each block to form a reference for the setting. The graduation 22 is calibrated in such a way that one division
of the graduation 22 corresponds to 0.01 mm movement of
the micro bore cartridge along its axis. In block 8 out side chamfering tool 27 is fitted. Method of use.
The method of use of the above special combination tool is described bellow.
The machining operations are to be done on the tube ends welded on the tube sheet. The tube sheet 28 is provided
with multiple numbers of holes 31 through which the tubes
29 are fitted and fixed by weld 30.
Before starting the machining of the actual job i.e. the tube
ends on the tube sheet, a mock tube welded in a mock
block (not shown in figure) which is similar to the actual assembly is placed on a CNC floor type boring machine, the machine spindle is aligned with tube center line.
The special combination tool is fitted in machine spindle. All
the three tools 19, 20, and 27 are set to proper radii with reference to center of the shank using vernier caliper.

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Using the preloaded CNC program cycle on the machine,
machining is carried out on the mock tube on mock block.
The CNC program cycle used is; Spindle rotation on - Rapid
feed on - Feed on - Feed stop - Retract.
All the machined dimensions are then checked and
compared with required dimensions on drawing and the
deviations are noted.
The tools are then adjusted using the setting nuts 17 and
18 on micro bore cartridges to eliminate the deviations. For
this, the screws 13 and 14 are first loosened; the nuts 17
and 18 are rotated to move the cartridges inward or
outward depending on whether the diameter is required to
be reduced or increased respectively, with the help of
graduations 22 on the nuts 17 and 18 and the fixed marks
on the blocks 6 and 7. The screws 17 and 18 are then
tightened. The out side chamfering tool 27 is adjusted
manually.
After all the adjustments are achieved the machine is now
taken to the actual job, which is set by the side of the mock
block.
Using the same program cycle, as used for the mock tube,
all the tubes on the job are machined with all the tools now
accurately set for finish machining.
Whenever a tool is changed the above setting procedure
using mock block is repeated.

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We claim,
1. A special combination tool comprising, spindle 2, tool main body 4, the tool main body 4 having face 5 perpendicular to the axis of the spindle 2, three blocks 6,7 and 8 fitted on the face 5, block 6 and 7 being spaced at 180 deg angle with respect to each other while block 8 being fitted spaced at 90 degrees with reference to the two blocks 6 and 7, two precision holes 9 and 10 being provided in the blocks 7 and 6 respectively, the axis of the said bores being oriented in perpendicular direction with reference to the axis of the spindle 2, two micro bore cartridges 11 and 12 being provided in holes 9 and 10 respectively for precision adjustment of the internal boring and chamfering tool 19 and external turning tool 20 in radial direction, the internal boring and chamfering tool 19 and external turning tool 20 being mounted on inner ends of micro bore cartridges 11 and 12 respectively, screw 13 and washer 14 being provided for tightening the micro bore cartridge 11 in position after setting while screw 15 and washer 16 being provided for tightening the micro bore cartridge 13 after setting, at inside end the micro bore cartridges 11 and 12 are being provided with fine threads 23 and 24 on which setting nuts 17 and 18 are being provided respectively, on the out side ends of the micro bore cartridges 11 and 12 two integral lugs 25 being provided on each cartridge, the lugs 25 being slide fit in the slots 26 being provided in holes 9 and 10; out side chamfering tool 27 being mounted on block 8.
2. The special combination tool as claimed in claim 1 where in the setting nuts 17 and 18 are being provided with graduation marks 22 on a step adjacent to face of the blocks 7 and 8, while the blocks 7 and 8 being provided with one fixed mark on each block to form a reference for setting with the help of the graduations 22.
3. The special combination tool as claimed in claim 1 where in the setting nuts 17 and 18 are being provided with a hexagonal step 21 on each nut to facilitate the setting by using a tool, like spanner.

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4. The special combination tool as claimed in claim 1 being used with method of use as follows;
a. a mock tube welded on mock block being placed
on the table of CNC floor type boring machine,
the spindle aligned with tube center;
b. the special combination tool mounted on the
spindle of the machine;
c. all the three tools viz. internal boring and
chamfering tool 19, external turning tool 20 and
the external chamfering tool 27 are being set to
the correct radii with respect to spindle axis by
using vernier caliper;
d. the mock tube being machined using the pre
loaded program to set the cycle as - spindle
rotation on - rapid feed on - feed on - feed
stop - retract;
e. the dimensions machined on the mock tube
being accurately measured; the deviations from
the dimensions given on the drawing being
noted and the tools being adjusted by loosening
the screws 13 and 15, rotating the setting nuts
17 and 18 as required to move the cartridges
inward or out ward depending whether the
diameter is to be reduced or increased, using
the graduations 22 and the fixed marks on the
blocks 6 and 7 for getting desired accuracy then
tightening the screws 13 and 15 to lock the
micro bore cartridges 11 and 12 in position to
complete the setting;
f. the machine being moved now to the actual job
i. e. the tube sheet 28 having the tubes 29
welded to it, spindle 2 being aligned with one of
the tubes and the machining program sequence
given in step "d" above being repeated for
accurate machining of the tube;
g. the machine then being moved to next tube and
same operation being repeated till all the tubes
on the tube sheet are finish machined.

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5. The special combination tool as claimed in claim 1 as substantially described hereinbefore, with reference to the accompanying drawings.
Mr. M. D. Bhate
Agent for the applicant
Dated this 10th day of April 2006

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Abstract:
The tubes on the tube sheet of a heat exchanger are presently machined by using four different tools in four different settings leading to high process time. Also the variations in the finished dimensions due to multiple settings are present. The above drawbacks are overcome by providing a single combination of three tools in to a special combination tool, which can perform all four operations in a single setting and single pass of the machine spindle. It is found that this combination tool can reduce the machining time up to 60% compared to the process used in the prior art.

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