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0st, 15, 1946.
Original Filed May 15, 1941
5 Sheèts-Sheet l
y Car/AMaxwe/Í
Original Filed May 15, 1941
5 Sheets-Sheet 2
fr 15, ÈS46.
` ' original Filed may 15, 1941
5 sheets-sheet s
Y `
Carl Á. Maxwell
@et 15, E946.
Original Filed May 15, 1941
5 Sheets-Sheet 4
. '
Patented Oct. 15, 1946
Carl A. Maxwell, Akron, Ohio, assignor to The
Babcock & Wilcox Company, Rockleigh, N. J.,
a corporation of New Jersey
Original application May 15, 1941, Serial No.
393,505, now Patent No. 2,375,235, dated May 8,
1945. Divided and this application January 25,
1944, Serial No. 519,591
2 Claims.
The subject matter of this invention is the ex
panding of tubular members and, in a more spe
ciñc sense, the expanding of metallic tubes against
(Cl. I‘Z9-457.5)
tures ranging from 1,000 F.-3,000 F. Necessarily,
the tubes to stand such pressures must be of
increased thickness and the manner of secure
ment of the tubes to the drums must be such
the walls of tube seats in which the tubes are
Ul as to enable the connections to withstand not only
In the manufacture of fluid heat exchange
high pressure but also the stresses set up by the
apparatus such as steam generators, metallic
variations in gas temperatures to which the tubes
tubes are ñxed in headers, drums, or tube sheets
and Ythe connections are subjected. Let us as
by iirst positioning the tubes within closely fitting
sume that the upper and lower headers are set
openings and then expanding the tubes tightly il) in position and that the tubes are fitted in the
against the Walls of those openings, and, with
drum tube seats by sliding them therein. The
the advent of increasing pressures (an increase
next step in the procedure is to expand the tubes
from 200 pounds per square inch to 2,500 pounds
to form pressure tight connections between the
per square inch within a period of thirty years)
tubes and drums. The prior practice has been
and the use of furnaces operating at higher and
to proceed with the expanding operation from
higher temperatures an increasing number of
an end of a tube toward its mid portion. Now, if
problems have been encountered in such expand
this practice is followed and a pressure tight con
ing operations. For example, with pressures in
creasing toward and beyond 2,000 pounds per
square inch, the walls of headers and drums have
correspondingly increased in thickness, and the
same is true of the walls of the tubes.
Steels of improved quality and increased
strength have also come into use and, when tubes
are to be expanded into tube seats in a ñve inch
nection is made by such an expanding operation
some of the tube metal will be caused to 110W
toward the other drum, this action resulting in
an increase of the length of the tube.
As to
the lengthening of the tube, this metal flow is
not particularly damaging on the ñrst tube be
cause that tube can slide in the tube seat of the
other drum, but when an attempt is made to
use this prior art procedure to expand the other
resistance to the expanding operation has been
end of the same tube in the other drum, there
encountered and greatly increased expanding
cannot be the same relatively free movement of
forces have been necessary.
the tube to- take care of the metal flow. How
The expanders of the prior art have operated 30 ever, the position of the drum may be modiñed
to expand the tube over the entire length of
to take care of such action. After this is done,
the tube seat, and as the tube seats have in
however, the positions of the two drums are fixed.
creased in length it has been necessary, with
Thereafter, when the same procedure is attempted
such prior art expanders to take excessively long
in the expanding of the successive tubes into
periods of time to expand even a single tube with
' the drums, a drum cannot be moved to take care
in a tube seat. There are instances where it
of such metal flow and tube lengthening because
has taken a plurality oi expander operators more
the securement of the ñrst tube has set the drum
than an hour to expand a single tube, under
spacing, and consequently the remaining tube
such conditions, and furthermore, this expanding,
metal will be put under objectionable stresses.
in such instances has involved large expanding
These may even be so great as to result in bend
forces and increased power.
ing of the tubes.
Furthermore, as tube seats have increased in
Attempts have been made to eliminate these
length and as tube Wall thicknesses have in
objectionable results of prior procedures by coun
creased, there has been excessive tube metal ex
ter-boring the drum tube seats. This has the
trusion consequent upon the expanding opera
' effect of decreasing the length of the tube seats
tions. Such excessive extrusion has been par
and correspondingly decreasing the metal ilows
ticularly damaging in the expanding of tubes in
resulting from the tube expanding operation.
steam generators involving a bank of tubes di
However, this practice of counter-boring tube
rectly connecting and fixed to the same drums
seats is objectionable because it reduces the
or headers. For example, let us consider the 50 strength of the drums in two ways. First of
expanding of the tubes of a water tube steam
all, by the removal of metal in the immediate
boiler in an upper drum and the lower drum at the
vicinity of the tube, and, secondly, by a conse
opposite ends of a large number of tubes which
quent decrease in ligament strength.
are to be subjected to a pressure of 1,000 pounds
Among the objects of this invention is the
per square inch and to furnace gas tempera 55 elimination of such difliculties as those above
wail of a drum of such improved steel, excessive
mentioned, the reduction of power and time re
quired to expand tubes within tube seats, and
the formation of improved tube seat connec
well as the advantage of increased torsional re
The suggested practice oi grooving tube seats
would not have the desired effect of increasing
the resistance to torsional forces tending to dis
The present invention eliminates many of the
rupt the tube seat. Furthermore, the machining
above indicated difficulties by a procedure which
the grooves of tube seats would involve consid
involves, as its initial step, the expanding of that
erable expense.
portion of a tube remote from the end oi the tube
In expanding a tube within a tube seat, there
and against that part of the tube seat metal
is a reduction in the thickness of the wall of the
which is adjacent to the wall of the drum or tube
tube, this reduction of thickness resulting from
sheet remote from the end of the tube. This
metal ñow tending to elongate the tube. The
initial expanding step is accomplished in such a
longer the tube seat the greater such metal flow
way that an optimum of tube metal flow is at
and the greater the tendency to elongate the
tained with a minimum of power consumption,
tube. Consequently, when a plurality of tubes
and in a greatly decreased period of time. This
are to be expanded between fixed headers or
is accomplished by having the roller expander
drums, the expanding operations may set up ob
element which does the preponderance of the ex
jectionable compression stresses in the tubes and
panding, of a small length relative to the length
the drums. Among other things, this invention
of the tube seats, other rollers of the expander
is intended to eliminate this undesirable tend
acting mainly to guide the expander apparatus 20 ency, while still presenting the advantages of the
and to stabilize it within the tube. After this
longer tube seats.
initial expanding operation, the active expander
High pressure drums are expensive because of
element is moved to a new and successive circu
the thickness of the metal utilized in their fabri
lar zone location toward the end of the tube from
cation, and because of the weight of the drums,
the ñrst location and the expanding is continued.
and therefore, it is important, that, in the use
In this Way, the flow of metal caused by the ex
of such drums, there be eiîective utilization of
panding operation is toward the end of the tube,
the maximum permissible ligament strength, to
and consequently there can be no tendency to
reduce drum wall thickness and thereby reduce
put the tubes of a bank of tubes under excessive
30 drum cost.
compressive stresses.
In distinction to some of the prior art practices,
In general, when tubes are expanded in a tube
such asV those involving the utilization of counter
sheet or into the walls of drums or headers, and
bored tube seats for high pressure boilers, the tube
are subjected to high fluid pressures, the tube
seats of the present invention, of the outside
and wall connections must be such as to resist
diameter of the tube, are carried completely
great forces tending to move a tube longitudi
throughout the drum metal and are more effec
nally with reference to the tube seat and to dis
tive in the providing of adequate ligaments. In
rupt the - connections. Additionally, there are
some grooved tube seats the length of the tube
forces exerted longitudinally of the tubes and
seat is but a fraction of the total drum thickness
through them to the tube seats, resulting from 40 and the seat is provided with a counter-bored
strains induced by temperature changes. There
opening extending initially from the tube seat
are also torsional forces which may tend to dis
and of a length suflicient to permit axial move
rupt the tube seat connection. These may result
ment of the tube. Attempts to roller expand
from various internal conditions such as temper
tubes into such tube seats have resulted in flow
ature changes, or >they may result from loading.
of metal into the portions of the tubes externally
These torsional stresses may be considered as
of the tube seats. It has been thought that such
exerted tangentially with reference to a tube so
metal flow would not be objectionable on account
that they have a tendency to rotate the tube in
of the limited length of the tube seat, but'l the
the tube seat and thereby destroy the fluid tight
pull-out strength of such tube seat connections
50 and their resistance to forces tending to develop
The length of a tube seat measured axially of
torsional displacements have been proven to be
a tube, is a major factor in the determining of
inadequate. This may have been due to deficien
the frictional resistance between a tube wall and
cles in the effect of prior art expanders or their
a tube seat wall, and, this resistance, in a coin
method of employment. The use of prior art
pleted joint should nullify forces tending to longi 55 roller expanders in attempts to form expanded
tudinally displace the tube with reference to the
tube seat connections with grooved tube seats
tube seat. The longer the tube seat, the greater
has not been satisfactory because the action of
the resistance, provided, of course, that the tube
the expanders has caused such flow of metal that
is expanded throughout the entire length of the
the expanded metal in a previously filled groove
tube seat. Additionally, it has been proposed that 60 would be subject to excessive shearing action
this pull-out resistance of a tube in a tube seat
when other grooves are filled. A first groove
be increased by the milling of grooves in the seat,
might be partially ñlled with tube metal, but the
the tube metal being displaced into these grooves
action of the expander in an attempt to fill a
by the expanding operation. With this practice,
successive groove has resulted in a shearing of a
metal within the first filled groove. Such shear
some of the tube metal would be subjected to
ing action is eliminated by the use of the ex
shearing stresses in resisting the forces which
pander of this invention, and by its use longer
during the operation of the apparatus, tend to
tube seats with a plurality of grooves may be
pull the tube out of the tube seat.
successfully employed. The use of the illustra
The torsional resistance to forces tending to
pull a tube out of a tube seat is also a function 70 tive expander in such tube sheets results in a,
ñlling of all of the grooves with iiowed tube metal
of the circumferential area of contact between
which remains integral with the metal of the
the tube and the seat and this type of resistance
expanded tube.
is greater in a long tube seat than it is in a short
The present invention also provides such tube
one. Long tube seats therefore have the advan
tage of a greater resistance to pull-out forQeS a5 ‘
seats that there may be maximum ligament
strengths. The illustrative tube seats .can also
'be machined at much lower cost, but these ad
vantages, along with the advantages of increased
pull-out and torsional resistance can be utilized
only when the method of expanding is such .that
the tube metal ilow resulting from the expanding
will not induce excessive stresses in the tube and
drum assembly. Such objectionable stresses are
avoided by a practice in which the flow of metal
during the expanding operation is toward the end
of the tube rather than toward the middle of the
This application is a division of my co-pend
ing application Serial No. 393,505, ñled >May 15,
1941 (now Patent No. 2,375,235), and the expand
ing method claimed herein is 'adapted for ex
panding tubes of great wall thickness such as
those required for installations operating at high
Fig. .6 is a transverse section on’the line B--S
of Fig. 5.
Fig. 7 is an assembly view showing an oper
ating mechanism connected to the expander as
the latter is inserted in the tube to be expanded;
Fig. 8 is mainly a sectional view of the Fig. 5
expander indicating the last step in the expand
ing of the tube into the tube seat;
Fig. 9 is an enlarged longitudinal section of the
Fig. 5 expander showing the relationship _of the
elements .in detail;
Fig. 10 is a partial plan of the expander cage,
illustrating the angular relationship of the center
lines of the expander rollers and the centerline
of the mandrel;
Fig. l1 is a sectional view of the barrel or vcage
`of the Fig. 9 expander showing the conformation
and relationships of the expander roll retention
pressures where the tube wall thickness may be
sockets in the cage;
in excess of 5/16", and the length of the tube seats 20
Fig. 12 is an end elevation of the expander bar
greater than three inches. Tube seats of such
rel or cage shown in Fig. 11;
characteristics result in expanding operations
Fig. 13 is a partial longitudinal section of the
which involve forces of high magnitude to cause
roller cage of the Fig. 1 expander, illustrating the
the necessary metal ilow.
relationships of the roller retention sockets.
In accomplishing the albove indicated results
This view is taken on the section line |3-Y-I3 `of
the present invention includes within its pur
Fig. 14;
View the expanding method effected by an ex
Fig. 14 is an end elevation of the expander-cage
pander apparatus in which stabilizing rolls are
illustrated in Fig. 13;
so arranged with respect to the remainder of the
Fig. 15 is a partial elevation of the Fig. 13
expander apparatus that they automatically 30 expander cage particularly indicating the oil"
cause the active portions of the expander rolls
to continuously move through the tube and
toward the end of the tube.
In general, the present invention may «be con
sidered as a method of expanding a heavy wall
tube into a tube seat, and more particularly, into
tube seats which are of lengths greater than the
diameter of the tubes to be inserted therewith,
set angular relationship of the axis of the cage
and the axis of one of the stabilizing rolls. The
position from which this elevation is taken may
_ be considered as indicated by the arrow läd;
Fig. 16 is a partial longitudinal section of the
Fig. 13 expander cage taken on the section line
IS-IB of Fig. 14; and
Fig. 17 is a longitudinal section showing the
by slower expanding, and working of the metal
operation of the Fig. 5 expander during an early
from the tube seat and remote from the tube end, 40 stage of the expanding operation.
toward the end of the tube, the illustrated appa
The expander illustrated in Figs. 1-4, inclu
ratus being such that it is self-advancing.
sive, and 5-8, inclusive, of the drawings maybe
The various features of novelty which charac
considered as a retractive roller expander in
terize my invention, in compliance with the Fed 45 which the expander rolls and the mandrel are
eral Statutes relating thereto, are pointed out
eccentric to the roller cage and to the tube to be
with particularity in the claims annexed to and
expanded. The expander barrel or cage ll! is a
forming a part of this specification, but, for a
steel body formed somewhat as a cylinder with
better understanding of the invention and the
such an external diameter that it will be readily
advantages possessed by it, reference should !be Ul C received within a tube to be expanded into a
had to the accompanying drawings and descrip
tube seat in the wall I4. The cage is formed 'with
tive matter in which I have illustrated or de
an eccentric bore to receive a mandrel l5.
’I’he mandrel is formed with a tapered section
scribed preferred embodiments of my invention.
I8, the surface of which causes the expanding
Other objects of the invention will also appear as
the following description proceeds.
55 roll 2D and the positioning and feeding rolls 22
In the drawings:
and 24 to move outwardly of the expander cage
when the mandrel is moved to the right (Fig. l)
Fig. 1 is a transverse section through a tube
mith reference to the cage and the tube seat wall
and tube seat assembly, and the illustrative roller
expander for developing a pressure tight joint
The advancement of the mandrel to tube ex
between the tube and the wall in which the tube 60
panding position, after the expander is inserted
seat is formed;
within the tube as indicated in Fig. 1, is caused
Fig. 2 is a transverse section of the Fig. 1 ex
rotation to the mandrel. In practice, the
pander, on the line 2_2 of Fig. 1;
mandrel is rotated by a motor 26 which is read
Fig. 3 is an assembly View showing mechanism
ily detachably connected to the squared end 28
for operating the illustrative roller expander
of the mandrel. During this Iortation and dur
which is shown in elevation;
‘ ing the initial stages of the tube expanding op
Fig. 4 is a combined longitudinal section and
eration, longitudinal advance of of the mandrel
is elïected by reason of the inter-engagement of
side elevation illustrating the last step in the ex
panding method in which the Fig. 1 expander 70 the screw threaded part of the mandrel with an
may be employed;
internally screw threaded sleeve 30 formed Iwith
a coupling extension 32, the latter being initially
Fig. 5 is a longitudinal section illustrating the
structure and mode of operation of another eX
pander which may be employed to eiîect the il
lustrative method;
held stationary by a wrench .cr Spanner.
The sleeve 3D is formed with a radial flange 34,
one face of which contacts the thrust bearing .36
disposed at the bottom of a recess in the end of
the cage I0, the sleeve 3U being confined between
the bearing 38 and the locking ring 38 screw
threaded into the cage I0, as shown.
The distance to which the Fig. 1 expander ex
tends into the tube l2 is determined by the ad
justment of a stop sleeve 40 along the cage l0.
This sleeve is locked in a predetermined posi
tion by the set screw 42.
When the sleeve 30 is thus held stationary the
rotation of the mandrel causes it to move to the
right so as to force the expanding roll 2B and
the stabilizing rolls 22 and 24 against the internal
surface of the tube l2.
When the frictional resistance resulting from
the contact of the tube and roller surfaces
reaches a certain degree, the rolls 20, 22 and 24
A comparison of the 4extent, of the surface of
the expander roller 20 in contact with the metal
of the tube l2 during the actual expanding op
eration to the sum of surfaces of the position
begin to rotate on their own axes as planet gears
ing and feeding rollers 22 and 24 in similar con
tact will indicate the ratio of roller surface which
is actually expanding the tube. All of the ac
tual expanding is done by the roller 20, and thus ‘
there is a very great reduction of momentary
flow of tube metal, in comparison with other ex
panders which use a plurality of rolls each of
which accomplishes the same degree of expand
In the present instance, the larger rolls, 22 and
24, serve to stabilize the expanding action and
cause the automatic advance of the expander out
of the tube.
Now referring to the expander indicated in
and, consequently, the cage I0, operating some
Figs. 5-12, inclusive, there is a cylindrical cage
what in the nature of an orbit gear, is also ro- ‘
'l0 formed at one end with three retention sockets
tated, but at a different rate. As this operation 20 ‘Il-_13 for the similarly formed expander rollers
continues the expanding roller 20, guided and
'I4-16. These sockets are formed with side walls
stabilized within the tube by the rolls 22 and 24
which are converging, or re-entrant at positions
exerts increasing pressure radially outwardly on
Bil-85 adjacent the periphery of the cage.
the inner wall of the tube l2 and causes the tube
metal to flow axially of the tube, and toward the 25
right hand end of the tube (Fig. 1). At the same
time, due to the differential taper of the rollers
and the mandrel, and due to the 2 degree angu
lar relationship (lead angle) of the mandrel cen
ter line to the center lines of the positioning and 30
feeding rollers 22 and 24 (see Fig. 15) the rollers
begin to advance the entire expander toward the
right of the position in which it is indicated in
Fig. l. These relationships are such that the
tendency of their combined action to advance 35
the expander overcomes the tendency of the ex
panding roll to mount the tapered portion of the
The retention sockets 'l l-13 are also so angled
with respect to the center line EF (Fig. 10) of the
cage and the mandrel that their center lines pre
sent the 2 degree angle GKE to the mandrel
center line. The expander rollers 14-16 have
their center lines in uniform angular relationship
to the cage center line EF so that, the roller ex
panding operation will involve a factor having a
tendency to automatically feed or advance the
expander from the initial expanding position in
which it is shown in Fig. 5, to the right outwardly
of the tube 90 and its tube seat in the wall 92.
The mandrel 94 is formed with an active expand
ing section 9B tapered ïag" to the inch, a taper so
selected that the mandrel surface active in en
After the bite of the expanding roller 20 into
gagement with the expanding rollers will be pre
the tube metal reaches the desired degree, the
sented to the rollers at an angle slightly greater
Spanner is removed from the coupling 32, and
than that which will permit the self-feeding
the above indicated relationship of forces there
action of the rollers 14-16 to surmount the man
after produces an automatic advance of the ex
drel. In other words, the taper of the mandrel
pander out of the tube.
constitutes an angle slightly greater than one
The angularity of the center lines of the posi- ~' which the self-feed action of the rolls will sur
tioning and feeding rolls 22 and 24 with respect
mount. Thus the thrust of the mandrel, in the
to the center line AB of the mandrel (Figs. 14
main part of the expanding operation will be
and 15 of the drawings) illustrates one of the
always toward the front of the mandrel (or its
factors producing the automatic advance, or self
left hand end as indicated in the drawings) . This
feeding action of the expander out of the tube.
thrust is taken by the bearing 98 from the cou
The line CD may be considered as representing
pling collar |00 which has an annular flange |02
the center line of the roller 22 mounted in the
confined between the bearing 98 and a lock collar
retention socket 50 of the cage I0. As indicat
H14. All of these elements are disposed within
ed, the lines CD and AB are disposed at an angle
of 2 degrees.
The retention socket 50 for the roller 22, as
well as the sockets 52 and 54 for the rollers 24
and 2G, respectively, may be described as formed
with walls which are re-entrant at positions such
as 55-(59, inclusive, adjacent the periphery of
the cage l0. This construction prevents the
rolls from falling out of their operative positions
around the mandrel I6.
The sockets are otherwise shaped within the
annular portion of the cage IIJ so as to permit
the rolls to move freely radially with respect to
the cage.
After the rolls 20, 22 and 24 are inserted in the
sockets 50, 52 and 54 they are retained therein
by a closure ring 62 corresponding in external
contour to the left hand end (Figs. 1 and 2) of
the cage. This ring is held in its operative posi
tion by a stud screw 64 fitting within an inter
nally screw threaded bore 66 in the end wall of
the cage.
a recess in the right hand end of the cage as
Each of the rollers 'I4-76 has a central portion
llû which is tapered, the taper of this portion
being slightly less than one-half the taper of the
mandrel. Beyond this tapered portion HU each
roller has a portion H2, the taper of which is
slightly greater than one-half the taper of the
mandrel. Thus the stabilizing portion of H0 of
each of the rollers 'I4-_16 rests against the man
drel and does the initial part of the expanding
and the portion H2 of the roller (the surface of
which is parallel to the axis EF of the tube) does
the final or heavier part of the expanding.
In the operation of the expander shown in Figs.
5-12 the collar |20 is adjusted along the cage 10
and ñxed thereon to determine the extent of the
expander within the tube. Then the expander
is placed in the tube in the position in which it
is shown in Fig. 5 with the collar |20 contacting
the end of the tube 90. Then the coupling collar
|00 is held stationary with a wrench or spanner
and an air motor 130 is employed to rotate the
mandrel through easily detachable engagement
with the polygonal coupling end 132 until the
rollers 'id-_16 are moved radially outwardly of
the cage 'i9 suñ‘iciently to expand the tube. Then
the coupling or nut mi! is released and the turn
ing of the mandrel operates to maintain the ex
panding pressure and automatically advance the
expander toward the adjacent end of the tube.
Considering the expander of Figs. 5-l2 to be
employed in securing the ends of the tubes of a
bank connecting two drums, the purpose of the
expander is to roll the tube from the outside of
the drum wall toward the inside, thus bringing 15
all axial flow movement of the tube metal, due
to the expanding operation, toward the inside of
the drum. With this manner of expanding-no
stresses are set up upon the intermediate portions
of the tubes between the drums. Also, the ex 20
pander rolls the tube with the major part of the
tube metal flow limited to a reduced portion of
the tube seat at any one time. This tends to pro
duce maximum holding power of the tube with a
the drawings is not claimed in this application
but is claimed in a co-pending application, Serial
No. 519,141, filed on January 21, 1944.
What is claimed is:
1. A method of retractively expanding tubes
into tube seats in a wall of a pressure part; said
method including an initial tube expanding oper
ation limited to and continuously advancing over
a narrow circumferential zone the width of which
is but a fraction of the length of' the tube seat,
said initial tube expanding operation being ef
“ected at a position adjacent the end of the tube
seat remote from the nearest tube end, stabilizing
and advancing the expanding operation by guid
ing reactions against internal surfaces of the tube
over an area and a circular zone of an axial extent
much greater than the narrow zone of the initial
expanding; subsequently repeating said expand- '
ing in a continuing expanding operation in con
tiguous Zones successively nearer the adjacent
end oi the tube; said initial expanding operation
involving the maximum tube expanding force of
the method; maintaining said maximum force
beyond the initial expanding operation; and con
minimum stress on the tube seat. Also, with the 25 stantly limiting the application of the expanding
force to a minor circumferential segment.
tive method much less power is required for oper
2. The method of retractively expanding the
ating the expander.
end portion of a metal tube into a tube seat
With further reference to Fig. 9 of the draw
ings, it will be seen that the center line TW of the 30 formed in a metal wall, the method comprising
initially expanding and drawing the tube metal
roll 'i4 forms an angle of 31/2° with the center line
by a rolling action advancing circumferentially
EF of the mandrel or the tube. This relationship
of the tube, exerting the maximum expanding
of parts, together with the relative degrees of
force of the initial action in a narrow zone limited
taper of the mandrel and roller surfaces indicates
to a position adjacent the wall surface at the
one factor in construction of the illustrative
illustrative apparatus employed in the illustra
greater distance from the adjacent tube end to
mechanism which tends to cause the action de
lock the tube to the wall at that position, then
continuing a like expanding and drawing opera
Fig. 17 illustrates an early stage of the expand
tion by a rolling action advancing helically of the
ing operations, the straight line RS when com
pared to the curved line RUS indicating the ex 40 tube toward the opposite surface of said wall and
away from said locked position toward the adja
tent of deformation of the tube in the expanding
cent end of the tube, constantly limiting the ap
operation. The straight line RS is intended to
of the maximum force of the expanding
indicate the interior surface of the tube before
and drawing eiîect of said rolling action at all
expansion, and the curved line RUS, the surface
of the tube after expansion. An inspection of 45 stages of the continued expanding to a circum
ferential zone the width of which is but afraction
this figure will show that the portion H2 of the
of the length of the tube seat, and maintaining
roller 'M has its active surface at a greater dis
an expanding force of the order of the maximum
tance from the line RS than the stabilizing por
of that of the initial action for a substantial part
tion lli), or the remainder of the roller.
the expanding method beyond the zone of the
The speciñc apparatus involved in the embodi 50 initial
ment shown in Figs. 1, 2, 3, 4, 13, 14, 15, and 16 of
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