Apparatus and method for expanding and shaping tubular conduits

A tool for reshaping or expanding metal tubular material includes an expandable mandrel having a plurality of duplicate spreader segments held in a cluster by an elastic O-ring about a wedge-shaped cam, each of the segments including an external, curved wall having a curvature corresponding to a curvature of an external curved wall in every other segment such that when all segments are equally spaced a predetermined amount, they form a cylinder having gaps between adjacent spreader segments for contact against an internal surface of the tubular material for reshaping or expanding said tubular material. The wedge-shaped cam includes a plurality of external faces corresponding to a number of internal spreader segment faces sloped to converge toward a front, mandrel-insertion or forward end of the cam and shaped complementary to the shape of the internal spreader segment faces for sliding engagement of the segments over an adjacent external face of the cam. These segments are kept axially aligned during expansion to maintain a substantially uniform mandrel cross-section during tubular stock expansion.

FIELD OF THE INVENTION 
The present invention is directed to a method and apparatus for expanding 
and/or shaping tubular conduits. More particularly, the present invention 
is directed to a method and apparatus for reshaping or expanding the 
internal diameter of any tubular conduit utilizing an expandable segmented 
mandrel and an internal driving wedge. In operation, the internal driving 
wedge is forced into an internal diameter of the segmented mandrel to 
expand the spreader segments against an interior diameter of the conduit 
to be expanded or reshaped to round or otherwise reshape the internal 
diameter of the conduit. 
BACKGROUND OF THE INVENTION AND PRIOR ART 
Other tools have been developed for reshaping and restoring damaged or 
deformed tubular stock, such as the piping of automobile type exhaust 
systems, as shown in my prior U.S. Pat. No. 3,324,701. One of the 
disadvantages associated with the tool described in my prior U.S. Pat. No. 
3,324,701 is that a threaded handle has to be turned in order to expand a 
plurality of expandable segments prior to forcing the expandable segments 
into tubular stock for reshaping the tubular stock. The expandable 
segments are set initially to a desired diameter by axial movement of a 
wedge or cam member threaded to a central spindle or shaft. The stock is 
reshaped by forcing the expanded segments, having tapered leading edges, 
into the stock and then removing the tool, further expanding the segments, 
and again forcing the segments into the stock to further reshape the 
interior of the stock by means of a hammer blow applied to the handle of 
the tool. The repeated removal and expanding of the device as well as the 
cumbersome wedge extending from the insertion end of the device makes its 
use very difficult. 
Another disadvantage of U.S. Pat. No. 3,324,701 is that the spreader 
segments can become misaligned axially with each other during tubular 
expansion since there is no means to prevent the individual spreader 
segments from sliding axially on the cam. Lack of axial alignment 
adversely affects the uniformity of the tubular stock expansion because 
the cross-sectional geometry of the expanded mandrel becomes less like a 
circle when the segments are misaligned. The cross-sectional geometry of 
the mandrel during expansion determines the final cross-sectional geometry 
of the tubular stock that is expanded. Thus, axially misaligned spreader 
segments can result in tubular stock being expanded into substantially 
non-circular and somewhat unpredictable cross-sections. 
U.S. Pat. No. 4,753,101 overcomes the disadvantage of the threaded handle 
that had to be turned; however, it still requires an impact to the wedge 
for the segments to expand radially. Furthermore, it too has the 
disadvantage of spreader segments becoming axially misaligned during 
tubular expansion, causing substantially non-circular expansion of the 
tubular stock. Also, upon maximum expansion, subsequent impacts or shocks 
caused a transfer of axial force from the cam member flange directly into 
spreader segment flanges at an end edge of the mouth of tubular stock. 
This resulted in axial misshaping of the tubular stock mouth from the 
axial forces. 
Another tool, shown in FIG. 1, accomplishes tubular stock expansion without 
an axial impact by means of a hammer or the like. In that tool a bolt 1 
runs through the hollow center of an internally threaded cam 5. Cam 5 is 
placed inside tubular stock 32, with the narrow end 7 of cam 5 facing 
mouth 135 of tubular stock 32. When bolt 1 is rotated, cam 5 is drawn by 
bolt 1 toward mouth 135 of tubular stock 32. Since cam 5 is shaped as a 
wedge, with its narrow end 7 facing mouth 135 of the tubular stock 32 to 
be widened, mandrel 13, comprised of 4 segments 20, receives a radial 
force when bolt 1 draws cam 5 toward mouth 135 of tubular stock 32. This 
tool, however, also has the disadvantage of spreader segments 20 becoming 
axially misaligned with each other, causing the final geometry of the 
tubular cross-section to be substantially non-circular. This results from 
lack of any axial alignment means associated with the forward, 
mandrel-insertion ends 23 of the spreader segments 20. 
Another disadvantage is that the amount which tubular stock 32 can be 
widened is limited by the tubular stock's diameter d1. This is so, because 
cam 5 must fit inside tubular stock 32 and the dimensions of cam 5 
determine the amount of tubular expansion which can occur. 
A disadvantage shared by some of the prior art is that a tap on the outside 
of the tubular stock is required for removal of the device from the 
tubular stock upon completion of tubular stock expansion. The device of 
the present invention can be removed smoothly from the tubular stock, 
without a tap, upon completion of expansion. 
SUMMARY OF THE INVENTION 
The above disadvantages of the prior art have been overcome in accordance 
with the apparatus of the present invention. In accordance with the 
apparatus and method of the present invention, a pyramid-shaped wedge or 
cam member is forced against internal surfaces of spreader segments by 
rotation of an internally threaded cylinder over a threaded bolt or the 
like. The resulting axial movement of the wedge or cam member thereby 
forces the segments radially outwardly against the internal diameter of 
the tubular stock, thereby reshaping the tubular stock. The rotation of 
the internally threaded cylinder will force the wedge or pyramid-shaped 
cam member of the tool of the present invention into an expandable 
mandrel, comprised of the spreader segments, to increase the diameter of 
the expandable mandrel and force the segments against the internal 
diameter to expand, or remove deformities in, the tubular stock. 
In accordance with the present invention, the rotation of the internally 
threaded cylinder disposed through a central axis of the cam member, 
forces the cam member into the mandrel thereby forcing the spreader 
segments radially outwardly. Radial expansion of the mandrel is 
accomplished substantially without the spreader segments moving axially 
with respect to the tubular stock. In this manner, the individual segments 
are not forced into engagement with an end edge of the tubular stock mouth 
and, therefore, the segments do not further damage or deform the tubular 
stock. Further, because the axial force applied to the cam member is 
transmitted essentially only radially against the spreader segments, the 
mechanic can grasp the tubular stock without mishap while rotating the 
internally threaded cylinder. Rotating the internally threaded cylinder 
results in forcing the spreader segments radially outwardly and not 
axially into contact with the end edge of the tubular stock. 
In some embodiments, a cylinder, smaller in diameter than the pipe to be 
expanded, is attached to a forward, mandrel-insertion end of the bolt. 
This cylinder is operatively associated with the forward ends of the 
segments and keeps the segments axially aligned with each other during 
expansion. 
In accordance with a preferred embodiment of the apparatus of the present 
invention, means for stopping further insertion of the cam member is 
provided on the apparatus. This means operates independently of the edge 
of the mouth of the tubular stock to be widened, thereby protecting the 
mouth from sudden axial force. 
Moreover, removal of the apparatus of the present invention upon completion 
of expansion can be easily accomplished in comparison to prior art 
devices. In some prior art devices, upon completion of expansion, the 
expansion device becomes stuck inside the mouth of the tubular stock that 
is expanded. In order to remove such prior art devices from the tubular 
stock it became necessary to tap the side of the tubular stock, jarring 
loose the expansion device from the tubular stock mouth. 
The apparatus of the present invention is well suited to use with power 
tools, including hydraulic wrenches, since excess force from power tools 
will not deform the edge of the stock mouth beyond the deformation that is 
intended. Additionally, easy removal of the apparatus of the present 
invention from the tubular stock upon completion of expansion allows for 
rapid-action expansion compared to prior devices and facilitates use of 
power tools. Easy removal is particularly advantageous for wide expansion 
of tubular stock requiring more than one size mandrel for completion. In 
such wide expansions, easy removal allows mandrels to be changed quickly 
from small mandrels to large mandrels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to the drawings and initially to FIG. 2, there is shown a new 
and improved device, generally designated by reference numeral 10, for 
expanding and/or reshaping a tubular conduit. The device 10 includes a 
wedge-shaped cam member generally designated by reference numeral 12; and 
one or more expandable mandrels, generally designated by reference 
numerals 14 and 16. In a preferred embodiment each segment forming the 
mandrels 14 or 16 is held in an expandable cluster about the wedge-shaped 
cam member 12 by a cylinder 200, disposed adjacent the forward ends 42 of 
segments 26. In the preferred embodiment, the wedge-shaped cam member 12 
is in the form of a hexagonal pyramid having six identical external faces 
24 extending in uniformly converging relation in a direction toward the 
forward, smallest diameter end 22 of the wedge-shaped cam member 12, as 
shown in FIG. 3. Forward end 22 of wedge-shaped cam member 12 is the 
mandrel-insertion end of cam member 12. 
The expandable mandrels 14 and 16 include a number of separate and 
duplicate spreader segments 26 or 28, the number of segments corresponding 
to the number of faces 24 on the wedge-shaped cam member 12. Each segment 
has a forward, mandrel-insertion end 42, a trailing end 40, an internal 
face 30 and an external, curved wall 44, as shown in FIGS. 3 and 6. It is 
understood that the number of external faces 24 of the wedge-shaped cam 
member 12 and the number of duplicate spreader segments 26 or 28 of the 
expandable mandrels 14 or 16 can be other than six, in accordance with the 
present invention, so long as the number of external wedge faces 24 
corresponds to the number of internal faces 30 on the spreader segments. 
The interior faces 30 on each of the duplicate spreader segments 26 and 28 
of the expandable mandrels 14 and 16 are sloped complementary to the slope 
on each of the faces 24 of the wedge-shaped cam member 12. The sloped 
interior surfaces 30 of segments 26 and 28 slidingly engage the external 
faces 24 of the wedge-shaped cam member 12 as the wedge-shaped cam member 
12 is forced axially into the expandable mandrel. Such action expands the 
segments 26 or 28 radially outwardly without substantially forcing the 
expandable mandrel 14 or 16 or its spreader segments 26 and 28 axially 
into the tubular conduit 32. 
The spreader segments 26 and 28 of the mandrels 14 and 16 are maintained in 
sliding contact with the faces 24 of the wedge-shaped cam member 12 by 
flexible retainers or elastic O-rings 34, 36 and 38, as shown in FIGS. 2 
and 3. Elastic O-rings 34 and 38 are positioned near end surfaces 40 and 
42, respectively, of the larger expandable mandrel 16 to maintain the 
segments 28 in a cluster about the cam member 12. The smaller mandrel 14 
does not require O-ring 38 at its insertion or forward end since, due to 
its shorter length, O-rings 34 and 36 will maintain the segments 26 in 
position. Each segment 26 or 28 is disposed adjacent to and in contact 
with one of the faces 24 of the wedge-shaped cam member 12. An 
intermediate elastic O-ring 36, disposed adjacent to O-ring 34 helps to 
maintain the segments in axial alignment, after spreading. 
As best seen in FIG. 4, when the mandrel 14 or 16 is positioned in a 
cluster about the wedge-shaped cam member 12, the segments 26 or 28 have 
their interior faces 30 sloped complementary to the faces 24 of the 
wedge-shaped cam member 12. The interior faces 30 of each of the spreader 
segments 26 and 28 slope to converge toward the outer surface 44, from a 
front or leading surface 42, uniformly in a direction toward both a 
trailing end 150 of cam member 12 and a rearward surface 40 of each of the 
spreader segments 26 and 28. This construction maintains essentially 
cylindrical outer, tubular conduit-contacting outer surfaces 44 at each 
different position of the spreader segments 26 or 28 along the faces 24 of 
the wedge-shaped cam member 12. The longitudinal exterior surfaces 44 of 
the spreader segments 26 are maintained essentially parallel to a central 
axis of cam member 12 during expansion and contraction of mandrel 14. 
In accordance with one important embodiment of the present invention, each 
of the spreader segments 26 is initially shaped to have an outer surface 
44 with a radius of curvature such that when the spreader segments 26 are 
approximately centrally disposed axially with respect to the external 
faces 24 of the wedge-shaped cam member 12, the outer surfaces 44 of the 
spreader segments 26 form a perfect cylinder having a plurality of 
essentially equally spaced gaps 46 between each of the segments 26. Gaps 
46 are shown in FIG. 2. 
Since the outer surfaces 44 of each of the spreader segments are formed 
with a predetermined radius of curvature r, as cam member 12 is inserted 
into mandrel 14 beyond the point where external faces 24 of cam member 12 
are approximately centrally disposed axially with respect to the spreader 
segments 26, the radius of curvature of the spreader segments will be less 
than the radius of curvature of the tubular conduit 32. In this manner, 
the outer surface 44 of the segments will contact the interior tube 
diameter only at a central portion (about 1/3 to 1/2 of the central outer 
curved wall area). Similarly, as the segments are positioned toward the 
leading edge 22 of the cam member 12, the curvature of the outer walls 44 
will be greater than the curvature of the interior diameter of the tubular 
conduit so that the outer walls 44 will only contact the interior tube 
diameter at a surface area (1/3 to 1/2 of the total outer wall area) 
adjacent the longitudinal edges 45. To achieve the full advantage of the 
present invention, therefore, the mandrel should form a cylinder when 
approximately centrally disposed, axially, on the cam member 12, as shown 
in FIG. 2. 
The longitudinal central grooves 52 in each of the external faces 24 of the 
cam member 12 maintain the segments 26 or 28 circumferentially aligned in 
a line of travel centrally along each face 24 of the wedge-shaped cam 
member 12 during radial expansion and contraction of the segments 26 and 
28. 
These longitudinal, central grooves 52 in each of the faces 24 of the cam 
member 12 provide a guide path for receiving a centrally disposed raised 
rib 54 extending outwardly from each of the interior faces 30 of each of 
the spreader segments 26 or 28 to maintain each spreader segment 26 or 28 
centrally disposed, in circumferential alignment along each external wedge 
face 24 of the cam member 12 during radial expansion and contraction of 
the spreader segments 26 or 28. 
In accordance with a preferred embodiment of the present invention, as 
shown in the drawings, the cam member 12 and spreader segments 26, 28 are 
cast from aluminum. Aluminum functions without breakage because the axial 
force applied to a cam member 12 is essentially completely transferred 
into a radial force to the outer surfaces 44 of the segments 26, 28. 
Cam 12 has a hollow center 113 disposed axially along its entire length. 
Hollow center 113 receives a threaded bolt 115 and a cam-engaging member 
117. In a preferred embodiment an internally threaded cylinder 117 is the 
cam-engaging member. Internally threaded cylinder 117 is threadedly 
engaged to threaded bolt 115. In a preferred embodiment, threaded bolt 115 
is attached coaxially to cylinder 200 disposed adjacent to narrow end 22 
of cam 12. Cylinder 200 is narrower in outer diameter than the inner 
diameter of tubular stock 32, thereby allowing cylinder 200 to fit inside 
of tubular stock 32. A solid end 121 of internally threaded cylinder 117 
is capped with a nut 119 which can be rotated with respect to threaded 
bolt 115, causing internally threaded cylinder 117 to apply axial force to 
threaded bolt 115. A washer 145, preferably made of Hydex.RTM. 4301 
polycarbonate, is placed between nut 119 and the wide end 150 of cam 
member 12 to protect metal surfaces during rotation of internally threaded 
cylinder 117. A bearing or other implement may be used in place of washer 
145. Nut 119 remains outside of hollow center 113 of cam member 12. 
A force is exerted on cam 12 in the direction of narrow end 22 of cam 12 
when bolt 115 is drawn into internally threaded cylinder 117. The axial 
force exerted upon cam 12 in the direction of narrow end 22 of cam 12 from 
the rotation of internally threaded cylinder 117 exerts a radial force 
upon mandrel 14 which in turn expands mandrel 14 and tubular stock 32. 
Cylinder 200 keeps spreader segments 26 axially aligned as an axial force 
on cam member 12 is converted to a radial force applied to spreader 
segments 26. Cylinder 200 includes a trailing face 203, best shown in FIG. 
7, which is defined as the face of cylinder 200 disposed in sliding 
engagement with the forward ends 42 of spreader segments 26. Axial 
alignment of spreader segments 26 allows mouth 135 of tubular stock 32 to 
be uniformly expanded. Axially misaligned spreader segments 26 can result 
in a substantially non-circular mandrel 14 cross-section during expansion. 
Since mandrel 14 cross-section determines tubular stock expansion 
geometry, a mandrel 14 with a substantially non-circular cross-section 
during expansion produces a substantially non-circular cross-section in 
mouth 135 of tubular stock 32. 
In a more preferred embodiment, cylinder 200 is hollow at 154, an area 
facing forward ends 42 of spreader segments 26. Cylinder 200 will be 
referred to as hollow cylinder 205 in those embodiments which require a 
hollow cylinder. It is understood that many embodiments described with 
cylinder 200 would also operate with hollow cylinder 205 in place of 
cylinder 200. Hollow cylinder 205 is solid at 156, the side furthest from 
cam 12 and it is on the interior 158 of this solid side 156 of hollow 
cylinder 205 that bolt 115 is attached. Hollow cylinder 205 has the 
advantage of allowing bolt 115 to be drawn further into internally 
threaded cylinder 117, thereby increasing the maximum distance which cam 
12 can penetrate mandrel 14 and, in turn, increasing the diameter to which 
mandrel 14 can be expanded. 
In a preferred embodiment cylinder 200 also functions to stop bolt 115 from 
being drawn into internally threaded cylinder 117 so far that mandrel 14 
is expanded to an interior diameter greater than the outer diameter of 
cylinder 200. By keeping the interior diameter of mandrel 14 smaller than 
the outer diameter of cylinder 200, cylinder 200 prevents spreader 
segments 26 from sliding on axial surface 140 of cylinder 200. Were 
spreader segments 26 capable of sliding on axial surface 140 of cylinder 
200, said spreader segments would be capable of becoming misaligned, and 
this misalignment would become more pronounced with increasing degrees of 
expansion. 
Maximum expansion of mandrel 14 is defined as the amount of expansion which 
mandrel 14 has undergone up to the point at which cam member 12 cannot be 
inserted any further into mandrel 14. Maximum insertion of cam 12 is 
defined as the amount of insertion of cam 12 into mandrel 14 which has 
taken place up to the point at Which cam member 12 cannot be inserted any 
further into mandrel 14. FIG. 4 shows a device of the present invention at 
maximum expansion. 
There are a multiple means of limiting cam member 12 insertion to a 
particular distance into mandrel 14. These means of limiting cam member 12 
insertion include: (1) obstruction of forward end 22 of cam member 12 by 
face 203 of cylinder 200; (2) obstruction of flanges 61 of cam member 12 
by trailing ends 40 of spreader segments 26; and (3) obstruction of 
further rotation of internally threaded cylinder 117 by contact between 
solid end 121 of internally threaded cylinder 117 and an end 160 of 
threaded bolt 115. 
When rotational force is applied to nut 119 after maximum cam insertion has 
been achieved, that force is absorbed by various parts of the present 
invention. Cam member 12 insertion limiting means (1) is less preferred 
because threads 128 of bolt 115, end 22 of cam member 12, and face 203 of 
cylinder 200 absorb the force, resulting in wear on these parts. Cam 
insertion limiting means (2) is less preferred because undesired 
deformation of mouth edge 65 of tubular stock 32 may occur when mouth edge 
65 absorbs the force which is transferred axially from flanges 61 to 
trailing ends 40 of spreader segments 26 to mouth edge 65 of tubular stock 
32. 
In a most preferred embodiment, shown in FIG. 4, cam insertion limiting 
means (3) is utilized. In this most preferred embodiment bolt 115 and 
internally threaded cylinder 117 provide means for stopping further 
insertion of cam 12 into mandrel 14. This is accomplished by having the 
length of interior 195 of internally threaded cylinder 117 such that head 
160 of bolt 115 reaches the solid end 121 of internally threaded cylinder 
117 before cam member 12 contacts hollow cylinder 205. 
Solid end 121 of internally threaded cylinder 117 is preferably tapered 
where bolt 115 contacts solid end 121 of internally threaded cylinder 117 
during maximum insertion of cam member 12. End 160 of bolt 115 is 
preferably both tapered and lacking threads on a region 162 which is the 
portion of bolt 115 which contacts solid end 121 of internally threaded 
cylinder 117 during maximum expansion. These features are best seen in 
FIG. 5, which is an enlarged view of a portion of FIG. 4. 
In this most preferred embodiment, upon maximum expansion of mandrel 14, 
three gaps remain, as shown in FIG. 4. A first gap 170, best shown in FIG. 
5, is defined between the end 160 of bolt 115 and solid end 121 of 
internally threaded cylinder 117. Gap 170 reduces contact between bolt 115 
and solid end 121 of internally threaded cylinder 117, allowing easy 
reverse rotation of internally threaded cylinder 117 for removal of 
mandrel 14 from tubular stock 32. 
Preferably, end 160 of bolt 115 is tapered and lacks threads. In such an 
embodiment, threads 128 of bolt 115 do not absorb excess force when end 
160 of bolt 115 contacts solid end 121 of internally threaded cylinder 117 
at maximum expansion. Excess force, in such an embodiment, is absorbed by 
unthreaded end 160 of bolt 115 and by solid end 121 of internally threaded 
cylinder 117 at point of contact 162. 
A second gap 180 is defined between the trailing ends 40 of spreader 
segments 26 and the flange 61 on the wide end 150 of cam member 12. Gap 
180 prevents cam member 12 from transferring direct axial force to 
trailing ends 40 of spreader segments 26. An axial force applied from an 
inner surface 189 of cam member flange 61 on trailing ends 40 of spreader 
segments 26 would misshape end edge 65 of tubular stock mouth 135. An 
advantage of this embodiment is that cam member 12 insertion is stopped 
before flange 61 of cam member 12 contacts the trailing ends 40 of 
spreader segments 26. In this manner, excess axial force is absorbed by 
bolt 115 and solid end 121 of internally threaded cylinder 117 rather than 
end edge 65 of tubular stock mouth 135. 
A third gap 190 is defined between cam member forward end 22 and cylinder 
205. Gap 190 reduces stress on threads 128 of bolt 115, and reduces wear 
on both the cylinder 205 and the cam member 12. 
This embodiment is well-suited for application with power tools, including 
hydraulic wrenches, because the excess force applied by a power tool in 
rotating internally threaded cylinder 117 is absorbed by solid end 121 of 
internally threaded cylinder 117 rather than edge 65 of tubular stock 
mouth 135. Also, removal of the device of the present invention from mouth 
135 of tubular stock 32, following expansion, can be easily achieved using 
a power tool by reversing the drive direction of the power tool. 
Embodiments in which cylinder 200 stops cam member 12 from further 
insertion by direct contact with cam member 12, without gap 190, are less 
preferred. In these less preferred embodiments, bolt threads 128 undergo 
much stress when force is applied to internally threaded cylinder 117 
after further insertion of cam 12 is blocked by cylinder 200. Also, the 
contact between cam 12 and cylinder 200 at maximum insertion, in these 
less preferred embodiments, causes wear on those parts. 
In embodiments having a hollow cylinder 205, a groove 147 in cam 12 allows 
cam 12 to be inserted further into hollow cylinder 205 before a trailing 
edge 165 of hollow cylinder 205 blocks advancement of cam 12. Groove 147, 
by postponing contact between cam 12 and trailing edge 165 of hollow 
cylinder 205, reduces the stress experienced by hollow cylinder 205 when 
mandrel 14 is near maximum expansion. Groove 147 accomplishes this by 
enabling bolt 115 and internally threaded cylinder 117 to first absorb 
excess force. Mandrel 14 is near maximum expansion when cam 12 is near 
maximum insertion into mandrel 14. 
For spreader segments 26 to be prevented from sliding over axial surface 
140 of cylinder 200, the difference between the outside radius of cylinder 
200 and the inner radius of mandrel 14, measured to inside face 30 on 
forward end 42 of a spreader segment 26 while mandrel 14 is completely 
unexpanded, should exceed the amount of radial expansion that mandrel 14 
can undergo before rotation of internally threaded cylinder 117 is stopped 
by one of the aforementioned means. 
As best shown in FIG. 4, another advantage to the construction of the 
reshaping or expanding tool of the present invention is that the threaded 
bolt 115 can remain threadedly connected to cam engaging member 117 so 
that the threaded connection should not become contaminated with rust, 
dirt or other contaminants during use. The radial expansion of the 
mandrels 14 and 16, therefore, will not be impeded by contaminants lodging 
in the threaded connection. 
In the preferred embodiment, relative diameters of the smaller mandrel 14 
and the larger mandrel 16 are such that when the smaller mandrel is fully 
expanded, its diameter is larger than the diameter of the larger mandrel 
16, when mandrel 16 is completely unexpanded. In this manner, tubes having 
diameters across the full range of diameters from the diameter of the 
completely unexpanded smaller mandrel 14 to the completely expanded larger 
mandrel 16, can be reshaped or expanded utilizing the two mandrels 14 and 
16, employing a single cam member 12. 
EXAMPLE 
An example containing dimensions for an apparatus in which mandrel 14 is 
prevented from expanding wider than cylinder 205 is as follows: a mandrel 
14 with an inner radius of 9 mm, when measured to the inside face 30 at 
forward end 42 of spreader segment 26 while mandrel 14 is in a completely 
unexpanded state; said mandrel with an inner radius of 17 mm, when 
measured to inside face 30 at forward end 42 of spreader segment 26 when 
mandrel 14 has undergone maximum expansion. The difference between the 
outer radius of cylinder 205 (22 mm) and the inner radius of mandrel 14 
when mandrel 14 is completely unexpanded (9 mm) is 13 mm in this Example. 
The change in radius of mandrel 14 during expansion is 8 mm (17-9 mm). 13 
mm exceeds 8 mm. Thus, at maximum expansion, forward ends 42 of spreader 
segments 26 remain in contact with cylinder 205 and said spreader segments 
26 are kept in axial alignment since said spreader segments are prevented 
from sliding upon axial side 140 of cylinder 205. 
Additional dimensions of the device of this Example include: the slopes of 
faces 24 of cam member 12 are 9.degree.; the maximum distance which cam 
member 12 can be inserted into mandrel 14 axially is 55 mm. In this 
example, at maximum expansion, cam member 12 insertion limiting means is 
provided by contact between end 160 of bolt 115 and solid end 121 of 
internally threaded cylinder 117. 
As shown in FIG. 2, the device of the present invention is excellent for 
removing a circumferential indentation 66 in the tubular conduit 32, such 
as that caused by a pipe clamp or mitten clamp when two conduits are 
mechanically secured together, particularly automotive exhaust conduits. 
Similarly, end deformities 68 commonly encountered in tubular conduits are 
easily and unexpectedly removed in accordance with the method and 
apparatus of present invention. 
While there has been described what is at present considered to be the 
preferred embodiment of the invention, it will be understood that various 
modifications may be made therein which are within the true spirit and 
scope of the invention. For example, internally threaded cylinder 117 and 
bolt 115 could be interchanged by replacing cylinder 200 with a nut on the 
forward, mandrel-insertion end of bolt 115 and by replacing nut 119 with a 
cylinder attached coaxially to solid end 121 of internally threaded 
cylinder 117.