FIELD OF THE INVENTION
The present invention generally relates to the manufacturing of helical
coil heat exchanger portable wrap bending fixture. More particularly, this
invention presents a portable wrap bending fixturing apparatus suitable
for radius bending of tubes at on site, were there is very less space for
mounting any other bending unit. Even already bent tubes may be
formed in the perpendicular directions to the required radius and helix,
which would pave the way for the manufacture of compact helical coil
tube bundles.
BACKGROUND OF THE INVENTION
In helical coil heat exchangers, the tubes are cold formed into bundles.
Each row/layer consists of tubes with different start and ending points.
The end point will have wrap bending/wrapping. Fig-1 shows a tube
winding done over a mandrel along with the start and end/terminal
points. A number of tubes winding or tube coiling over a mandrel forms a
bundle. Excessive loading of tube for wrap bending without the use of
wrap bending fixture unit creates kink/dent in the bottom layer of the
tube. For example, in US06/251,951 to Herbert, bends are formed in
portions of low density by applying forces to said tube through the spines
along said portions of said low fin density. However, it is disclosed
further that in the bending process in which the various bends are
formed in the wound tubing, the spine fins along the bend are also bent
and damaged to some extent so that they cannot contribute to the heat
exchange with the same efficiency as the undamaged fins along the
straight portions of the tube.

In a helical coil heat exchanger, the space between the two layers of coil
is very less thus making effective utilization of available space and
designing of fixture for wrap bending becomes a complex process.
Thus, there remains a need for the development of a suitable fixturing
apparatus to be implemented in the manufacture the wrap bending of
tubes, particularly even suitable for making smaller-radius bends.
OBJECTS OF THE INVENTION
An object of the invention is to overcome the aforementioned and other
drawbacks existing in prior art systems and methods.
More particularly, it is an object of the invention to develop a portable
wrap bending fixturing apparatus to be implemented in manufacturing of
tube bundles of helical coil heat exchanger with wrap bending terminals.
Still another object of the invention is to avoid kink formation on the
bottom layer of the bundle.
Yet another object of the invention is to develop a portable wrap bending
fixturing apparatus for facilitating easy handling.
Further object of the invention is to develop a portable wrap bending
fixturing apparatus for minimizing the operator interference.
Still another object of the invention is to develop a portable wrap bending
fixturing apparatus suitable for manufacturing of varying diameter of
tube bundles.

Further object of the invention is to develop a portable wrap bending
fixturing apparatus suited for effective utilization of space available
between the two layers of tubes.
Yet another object of the invention is to develop a portable wrap bending
fixturing apparatus suitable to be implemented for any tube diameter.
These and other objects and advantages of the present invention will be
apparent to those skilled in the art after a consideration of the following
detailed description taken in conjunction with the accompanying
drawings in which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION
The present application discloses an apparatus for making wrap bending
of tubes so that the end/terminal point will lie in the same PCD (Pitch
Circle Diameter) of the coil. In an aspect, the wrap bending fixturing
apparatus includes a handling support (2) to which a handling cylinder
(1) is clamped. In another embodiment, the hydraulic cylinder (1) is
pivotally connected to a clamp pad (3), thereby facilitating forward and
backward movement of the clamp pad (3). In another embodiment, the
wrapping/wrap bending occurs during the forward movement. Further, a
clamp plate (5) is configured to clamp a tube (12) among the multiple
tubes via a bolt (4). Furthermore, the apparatus includes a locating pin
(6) movably positioned on a support plate (7) for engaging with a plurality
of grooves (11) arranged on a bottom of the wrap bending former (8), said
support plate (7) is welded to the handling support (2).

In another aspect, the present application discloses a method for wrap
bending a plurality of tubes (12) at an end point of a helical tube heat
exchanger. The method includes the step of applying hydraulic pressure
via a hydraulic cylinder (1) for effecting forward and backward movement
of a clamp pad (3) resulting in wrapping a tube according to profile of a
wrap bending former (8) during the forward movement of the clamp pad
(3). Further, the method involves the step of displacing a locating pin (6)
across the plurality of grooves (11) during the reverse movement of the
clamp pad (3) till completion of wrap bending of the tube.
The above and additional advantages of the present invention will
become apparent to those skilled in the art from a reading of the
following detailed description when taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The drawings refer to embodiments of the invention in which:
Fig.1 illustrates the tube (12) winding done over a mandrel with the start
and end points also being shown.
Fig.2 illustrates the major components of a portable wrap bending
fixturing apparatus.
Fig.3 illustrates the various stages starting with the locating pin (6)
inserted in a groove available at a bottom of the wrap bending former (8)
as in stage-1. Stage-2 and Stage-3 are shown with subsequently inserted
locating pin (6) to the next grooves and so on.

Fig.4 illustrates the wrap bending unit without wrap bending former (8)
particularly showing the clamp pad (3) is used along with the hydraulic
cylinder for applying load.
Fig.5 illustrates an isometric view of a wrap bending former (8), multiple
grooves (11), (9), (10).
Fig. 6 illustrates a clamp pad (3) having a profile same as the tube outer
diameter according to an embodiment of the present invention.
Fig.7 illustrates a locating pin (6) being used for radially locating the tube
with the wrap bending former (8).
Fig.8 illustrates a clamp plate (5) for clamping of tube.
Fig.9 illustrates clamp plate (5) design suiting different outside diameter
tube (12).
Fig.10 illustrates wrap bending of a tube so that the end point of the
tube (12) matches with the PCD of the coil.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Although the disclosure hereof is detailed and exact to enable those
skilled in the art to practice the invention, the physical embodiments
herein disclosed merely exemplify the invention which may be embodied
in other specific structure. While the preferred embodiment has been
described, the details may be changed without departing from the
invention, which is defined by the claims.

It will be apparent, however, to one of ordinary skill in the art that the
present invention may be practiced without specific details of the well
known components and techniques. In other instances, well known
components or methods have not been described in detail but rather in
Figures in order to avoid unnecessarily obscuring the present invention.
Further specific numeric references should not be interpreted as a literal
sequential order. Thus, the specific details set forth are merely
exemplary. The specific details may be varied from and still be
contemplated to be within the scope of the present invention. The
features discussed in an embodiment may be implemented in another
embodiment.
Moreover occasional references to the conventional techniques for radius
bending of tubes are made in order to better distinguish the present
inventive disclosure discussed later in greater detail. Few of the details
pertaining to the bending of tubes are well-known in the art, and
therefore, are described herein only in the detail required to fully disclose
the present invention.
Improving upon the conventional techniques discussed at length above
(background), in the present disclosure the inventive design of the
components forming a portable wrap bending fixturing apparatus as
shown in Figs. 1-7 clearly makes the portable wrap bending fixturing
apparatus as disclosed in the present application advantageous over the
existing arts as would also become clearer to the knowledgeable in the
art with the particulars of the aforesaid techniques being described below
in greater detail.

Turning now to Figures where the apparatus for making wrap bending at
the end points of helical tube exchanger are depicted. Fig. 1 illustrates
the tube (12) winding done over a mandrel with the start and end points
also being shown. Further, Fig.2 particularly, illustrates the primary
components of a portable wrap bending fixturing apparatus. It is shown
that the handling support (2) clamps the hydraulic cylinder (1).
Furthermore, in Fig.2, tube (12) is pressed with clamp pad (3) so as to
form the profile (10) given in the wrap bending former (8). The profile (10)
shows the groove made in the wrap bending former (8) and along this
profile (10), the tube (12) will be pressed by hydraulic action of the
cylinder (1). The profile (10) can be made according to the desired radius
requirement of the bend (8B). Hydraulic pressure is applied by using
hydraulic cylinder (1) and with clamp pad (3) resulting in the tube (12)
being wrapped in accordance with the profile of wrap bending former (8).
In another embodiment, the clamp pad (3) can be made of varying
diameter depending on the tube (12) diameter. Thus clamp pad (3) of
varying size can be manufactured depending upon the tube (12) diameter
for bending process. The wrap bending former (8) can be manufactured
by varying the diameter profile (10) and wrap bending radius (8B) which
will match with the bundle profile. Diameter of the tube (12) mentioned is
related to the outer diameter of the tube.
Fig.3 illustrates the stages, for example, 1, 2 and 3 of the successive
positions of the handling support (2) indicating the displacement of
locating pin (6) so as to obtain the wrap bending of the tube. In an
embodiment, the tube is clamped with clamp plate (5) with the help of
bolts (4). In a preferred embodiment, the wrapping/wrap bending occurs
only in the forward direction. The locating pin (6) will be shifted to
successive groove (11) and the clamp pad (3) will apply pressure on the
tube (12) for wrap bending process.

In Fig.4, the movement of clamp pad (3) in forward and reverse direction
is shown. It is noted herein, that the forward and reverse movement is
due to the hydraulic pressure as disclosed above. Further, in the forward
direction, the tube is wrapped according to the profile of wrap bending
former (8) and in reverse direction, the hydraulic load can be released so
that the locating pin (6) can be engaged with the next successive grooves
(11) available at the bottom of the wrap bending former (8) resulting in
wrap bending of the tube. The clamp pad (3) will apply pressure on the
tube (12) until the tube touches the profile (10) available at the bending
former (8). Hydraulic pressure will not be applied after the tube (12)
touches the profile (10) of the wrap bending former (8) and then the
successive grooves can be engaged for further bending. In forward action
of the hydraulic piston, the clamp pad (3) presses the tube (12) and in
reverse action the clamp pad (3) releases the tube (12). Thus, only in
forward action the bending of the tube (12) takes place. Moreover, “in”
and “out” shows the flow of hydraulic oil for actuating the hydraulic
piston for effecting up and down movement. As the piston moves down,
the clamp pad (3) attached to the piston end will press the tube (12)
against the profile (10) of the wrap bending former (8).In an embodiment,
the locating pin (6) is held in position with support plate (7) which is
welded to the handling support (2).
Further, the isometric view of the wrap bending former (3) is shown in
Fig.5. The inner profile (10) shows the groove path along which the tube
(12) may be wrap bended. The hole (9) shows the clamping arrangement
for the clamp plate (5) with the help of bolts (4). The groove (11) available
at the bottom of the wrap bending former (8) is for placing the locating
pin (6) on successive pressing. In a preferred embodiment, the locating
pin (6) is matched to one of the grooves (11) available at the bottom

portion of the wrap bending former (8). The portion (10) shows the inner
profile which gets matched with the bundle profile. Further, the inner
profile (10) made in the wrap bending former (8) should match with the
bundle profile. This will ensure that the tube (12) after bending will
match with the bundle profile.
Further, the bolt (4) along with the clamp plate (5) clamps the tube to
wrap the tube according to the profile of the bending former (8). In an
embodiment, the profile in the clamp plate (5) matches with the outer
diameter of the tube. Fig-9 shows the clamp plate (5) matching with the
outer diameter of the tube (12). Successively, the locating pin (6) is
placed in different grooves (11) through application of hydraulic pressure
which in an embodiment is applied by using hydraulic cylinder (1)
connected to the inlet and outlet of the hydraulic source (not shown).
Fig.7 illustrates a locating pin (6) being used for radially locating the tube
with the wrap bending former (8). In this, the line of action of the clamp
pad (3) and the center of the locating pin (6) will be at a straight line and
also it will pass through the center of the wrap (8A) of the bending former
(8). Furthermore, the wrap bending former (8) in an embodiment is
manufactured by using die steel material followed by the hardening
process. Further, the tube may be made of any material and of any
thickness suitable to be used for helical coiling. In an embodiment, the
wrap bending formers (8) are manufactured for the range of radius 100
mm to 250 mm and the same method can be employed for varying
diameter of tube bundle and tube diameter for which the clamp pad (4)
and bending former (8) to be altered suitably. The clamp pad (4) can be
made of varying diameter depending on the tube (12) diameter. Thus
clamp pad (4) of varying size can be manufactured depending upon the
tube (12) diameter for bending process. The wrap bending former (8) can

be manufactured by varying the diameter profile (10) and this profile will
match with the bundle profile.
The proposed invention relates to the development of
techniques/apparatus for wrap bending of coil terminal points which will
match with the pitch circle diameter of the coil. Fig-10 shows the pitch
circle diameter of a coil along with wrap bend. For a wrap bend, the end
point or terminal point will lie in the pitch circle diameter. The aforesaid
fixture is used for manufacturing of wrap bends of all bundle diameter of
helical coil heat exchanger. Tubes (12) are coiled in bundles for heat
exchanging. The terminal points are the points at which the tubes (12)
will end coiling. Now the tube end has to be bent in line with bundle
profile and finally to be matched with the end/terminal points. Fig-10
shows the end/terminal point of the tube after completion of the wrap
bending. Wrap bending will be done on the tube (12) so as to match the
bundle profile. For wrap bending of the tube (12) before matching to the
terminal point, this apparatus is developed.
The foregoing is considered as illustrative only of the principles of the
invention. Furthermore, since numerous modifications and changes will
readily occur to those skilled in the art, it is not desired to limit the
invention to the exact construction and operation shown and described.
While the preferred embodiment has been described, the details may be
changed without departing from the invention, which is defined by the
claims.

WE CLAIM:
1. A portable wrap bending fixturing apparatus for wrap bending a
plurality of tubes (12) at an end point of a helical tube heat
exchanger, wherein the helical tube exchanger comprises:
a plurality of layers of tubes which is wrapped into
helical coils, said helical coils further comprising of
tube bundles;
wherein the wrap bending fixturing apparatus comprises:
a handling support (2) to which a handling cylinder (1)
is clamped, said hydraulic cylinder (1) pivotally
connected to a clamp pad (3), thereby facilitating
forward and backward movement of the clamp pad (3),
wherein wrap bending occurs during the forward
movement;
a clamp plate (5) configured to clamp a tube among
the plurality of tubes via a bolt (4); and
a locating pin (6) movably positioned on a support
plate (7) for engaging with a plurality of grooves (11)
arranged on a bottom of the wrap bending former (8),
said support plate (7) is welded to the handling
support (2).
2. The apparatus as claimed in claimed 1, wherein the locating pin (6)
is matched with one or more of the plurality of grooves (11).

3. The apparatus as claimed in claim 1, wherein outer diameter of the
tube is matched with profile of the clamp plate (5).
4. The apparatus as claimed in claim 1, wherein the wrap bending
former (8) is made from a die steel material.
5. The apparatus as claimed in claim 1, wherein the wrap bending
former (8) is configured for wrap bending of tube of radius (8B)
ranging between 150 mm to 250 mm.
6. The method for wrap bending a plurality of tubes at an end point
of a helical tube heat exchanger, wherein the method comprises:
applying hydraulic pressure via a hydraulic cylinder
(1) for effecting forward and backward movement of a
clamp pad (3) resulting in wrapping a tube according
to profile of a wrap bending former (8) during the
forward movement of the clamp pad (3); and
displacing a locating pin (6) across the plurality of
grooves (11) during the reverse movement of the clamp
pad (3) till completion of wrap bending of the tube.
7. The method as claimed in claim 1, further comprising varying
diameter of tube and tube bundle by appropriately altering the
clamp pad (3) and the wrap bending former (8).