FIELD OF THE INVENTION
The present invention relates to a portable metal tube holding and bending
device for incremental bending of metal tubes
The invention further relates to a method of in-situ bending of metal tubes.
BACKGROUND OF THE INVENTION
In the manufacture of compact heat exchangers, helical tube bundles are used.
The helical tube bundles are made up of helically coiled tubes. Both ends of the
tube are formed to a required bend configuration using in-situ holding and
bending devices.
According to the existing practice, after making each coil, the following
operations are implemented:
1. The tube is held in position by a clamping arrangement.
2. A bending former and jaws are positioned.
3. A powered cylinder Hydraulic/Phenumatic/electrical is operably
attached to the device.
4. Tube bending to a required radius and angle is done.
However, limitations of free-length and operational space disallow usage of a
known tube bending unit to carry out all of the above operations. After
carrying out the in-situ bending , for clamping and end trimming of each tube

to maintain the required length of the tube bundle, the straight end of the
tube needs to be positioned inside a fixture ring. The degree of bend
achieved is determined by visual inspection and matching of the bend profile
with a 2 D template.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a metal portable metal
tube holding and bending device for incremental bending of metal tubes.
A further object of the invention is to propose a process in-situ bending of
metal tubes.
These and other objects and advantages of the invention will be apparent
from the ensuing description.
SUMMARY OF THE INVENTION
According to the invention, clamping devices, tube holding means including
tools and accessories required for tube bending are custom-designed,
developed and manufactured. The clamping / holding devices, bending
tools/accessories during operation, need to be adjusted in various pitch circle
diameters and tube orientations in the coil assembly. Also the bending
reaction, requires to be absorbed in the bending unit itself. For tube bending,
an actuable cylinder and power pack are integrated to the in-situ tube
bending unit, for finer control.

Because of constraint in space, even wrap bending decided for the invention
could not be done in a single continuous stroke of the follower jaw/former.
Unlike the conventional follower jaw which is straight, the invention
configures the follower jaw itself to further act as a former with a profile
corresponding to the tube profile. To transfer movement of the follower jaw
from the powered cylinder, a shaft holding the follower jaw is used and
guided inside a slot made in a base plate. Tube bending is carried out with
precisely determined increments/angle of bend. This incremental bending is
achieved by making incremental wrapping movement of the follower jaw
against the fixed former. Multiple matching holes provided in the base plate
and the bending former in combination of a pin enables locking of relative
movement of the former and the base plate. Likewise, by locking the former
progressively in the holes one after the other, and actuating the cylinder, the
required radius and angle of bend is formed. Apart from the radius and angle
of bend, associated forming related requirements like tube thinning, tube
ovality and flattening are also achieved.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
1. Figure - 1 Schematically illustrates a portable metal tube holding and
bending device for in-situ bending of metal tubes according
to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in Fig. 1, the in-situ bending unit consists of a tube clamping
means (7, 8) , a bending and follower jaw means (2, 5) and a powered
(hydraulic/pneumatic/electric) unit (3). A base plate (1) holds the powered
cylinder (3), the bending former (2) in position and provide a rigid platform
for the bending to take place. Initially, a straight portion of a tube (10) is
gripped using the pair of Clamping jaw (7) and the Clamping pad (8). On
actuation, the powered cylinder (3) allows movement of the Follower jaw (5).
A holder (4) and a Shaft (6) ensure that a desired stroke given by the
cylinder (3) is transmitted to the follower jaw (5) and the position of the
former/tube is retained by means of a lock pin (9).

WE CLAIM:
1. A portable metal tube holding and bending device for incremental
bending of metal tubes comprising :
- a base plate (1) holding a powered cylinder (3) and a bending-cum-
follower jaw (2, 5) in position for performing bending operation;
- a clamping jaw (7) including a clamping pad (8) for gripping a straight
portion of the tube (10);
- an actuation cylinder (3) on activation allows movement of the follower
jaw (5);
- a shaft (6) with a holder (1) transmits a desired stroke given by the
cylinder (3) to the follower jaw (5), a lock pin (9) retaining the former
with the tube (10) in the operating position;
- the follower jaw (5) when further actuated by the power cylinder (3)
wrapping the clamped tube (10) over the bending former (2) to achieve
incremental bending; and
- a control means incorporated in the powered cylinder (3) in association
with the locking pin (9) monitors and control the start/stop of the bending
device.
2. A process for incremental of bending metal tubes having various
diameters and pitch circle diameters, wherein a powered follower jaw,
configured in a shape of a grooved roller is operated and wrap bending of
straight tube against a fixed former with a locking means is achieved.

3. The process as claimed in claim 4, wherein bending of tubes are carried
out in various positions to obtain the desired bend of the tube.

The invention relates to a portable metal tube holding and bending device for
incremental bending of metal tubes comprising a base plate (1) holding a
powered cylinder (3) and a bending - cum - follower jaw (2, 5) in position for
performing the bending operation; a clamping jaw (7) including a clamping pad
(8) for gripping a straight portion of the tube (10); an actuation cylinder (3) on
activation allows movement of the follower jaw (5); a shaft (6) with a holder (4)
transmits a desired stroke given by the cylinder (3) to the follower jaw (5), a lock
pin (9) retaining the former with the tube (10) in the operating position; the
follower jaw (5) when further actuated by the power cylinder (3) wrapping the
clamped tube (10) over the bending former (2) to achieve incremental bending;
and a control means incorporated in the powered cylinder (3) in association with
the locking pin (9) monitors and control the start/stop of the bending device.