Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to an expansion machine
suitable for radially expanding a tubular member, and to a
method of securing a tube in a tube-plate by using the
expansion machine.
More particularly, but not exclusively, the
present invention is applicable to the expansion in a sealtight
manner of a tube in a tube-plate o a heat-exchanger, especially
large heat-exchangers made of costly materials such as stain-
less steel, aluminium or bronze, which, on account of the high
cost of the material used, cannot be constructed with solid
tube-plates ~or reasons of economy.
As is known, the tube bundle of a tube bundle heat~
exchanger is supportcd at its ends by two tube-plates which
have bores in which the tubes of the tube bundle must be
secured in a sealtight manner. One conventional techniquc
for this securing involves welding each tube with respect
to the tube-plate. However, this technique, in addition
to involving considerable expense and requiring a long working
time, suffers from the disadvantage that it cannot be applied
universally as there are pairs of materials, from which the
tubes and tube-plates, respectively, are formed, which cannot
be welded together.
Another conventional system which requires the
use of solid tube plates of considerable thickness, involves
forcibly introducing the tubes into the bores of the tube-
plates and relying on expansion of the tubes. However, this
technique suffers from the defect that it does not always
afford a satisfactory tight seal between the tube and the
tube-plate. In fact, the expansion of the tube concerned
against the tube-plate provides an adequate seal only when
tubes having a great thickness and a small diameter are used,
that i5, tubes which are sufficiently stiff to retain the
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deformation caused by the expansion. In contrast, when tubes
having a thin wall and a large diameter are used, an elastic
contraction is always experienced after the expansion, thus
making it virtually impossible to Pbtain a satisfactory seal.
From the foregoing, it will be appreciated that the
aforementioned conventional techniques cannot practicably be
used in the manufacture of a large heat-exchanger in which
the tube-bundle is composed of tubes having a large diameter,
especially when such tubes are made of a special material and
thus are expensive, and therefore they are used with thin walls
or the sake of economy.
According to one aspect of the present invention,
there is provided an expansion machine suitable for radially
expanding a tubular member, the machine comprising an actuatable
double-acting ram having a housing in which a piston is
reciprocable under fluid pressure, the piston having a rod
extending through and beyond the housing; an integral,
elongate, annular r resiliently deformable plug which is formed
of rubber or another plastics material, is idly and coaxially
located on a portion of the rod extending beyond the housing,
and tapers in its opposite end regions, as viewed in longi-
tudinal section; and two abutment means acting or capable
of acting on opposite end regions of the elongate plug during
actu~tion of the ram in one sense, for compressing the plug
longitudinally so as to cause radial expansion of the plug,
the abutment means each having an annular, tapering groove
in that face which confronts the plug for accommodating a
tapering end region of the plug.
According to a second aspect of the present
` 30 invention, there is provided a method for securing in a
sealtight manner by expansion a tube in a bore of a bored
tube-plate, in which the tube-plate is composed of two
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- stamped thin metal sheets which are arranged substantially
parallel to one another and have in correspondence wi-th
confronting bores generally cylindrical annular lips; which
method comprises locating the tube in a pair of confronting
bores, radially expanding the ~ube by means of an expansion
machine according to the first-mentioned aspect, in regions
of the tube on either side of the tube-plate and opposite
the annular lips, thereby causing deformation of the annular
lips; càusing or permitting the plug to con-tract radially,
and withdrawing the machine from the tube.
The present invention makes it possible to provide
an efficient sealtight anchoring of a tube in the corresponding
bore of a tube-plate both quickly and economically, to a
large extend irrespective of the diameter and the thickness
of the tube and irrespective of the materials used to fcrm
the tube and the tube-plate respectively.
During use of the expansion machine of the present
invention, the axial compression of the plug gives rise to
an elastic deformation in the radial direction of the plug,
this deformation having as a result the forcing of the tube
in the radially outward direction, whereby expansions are
created in the tube in correspondence with the outer edges of
the confronting bores of the two metal sheets which form the
tube-plates and in the intermediate zone internally of the
two sheets between the annular lips, so that the tube is
locked permanently in a sealtight manner to the sheets, and
an elastic deformation is induced in the annular lips which
thus ensures the obtention of an efficiently tight seal.
Conveniently, the ram is actuatablé under the
influence of air or by a hydraulic medium.
Preferably the abutment means comprise two rings
both mounted around the rod, with one ring secured with
respecttO the free end region of the rod and the other ring
movable with respect to the rod but restrained from movement
in one direction by the housing.
Conveniently, the rin~s are formed of a nylon.
Preferably the machine includes means for adjusting
the stroke of the piston of the ram.
The stroke-adjusting means can comprise a sealing
and piston-abutting adjustable member which can be adjusted
in the axial direction by shims.
Preferably the annular, tapering grooves each have
generally the shape of a V.
The housing of the ram may be equipped with a handle
having a tri~ger for controlling fluid feed to the ram.
For a better understanding of the present invention
and to show how thc same may be carried into cffect, reference
will now be made, by way o~ example, to the accompanying
drawings, in which:
Figure 1 is a fragmentary view in cross-section of
a tube-plate, in the bores of which are tubes shown in
longitudinal section, there also being shown mainly as a
longitudinal section an expansion device in accordance with
the present invention; and
Figure 2 is a longitudinal section through the
expansion device shown in Figure 1.
Referring first to Figure 1, there are shown two
paralIel, stamped metal sheets 1, 2 of reduced thickness
which together constitute a tube-plate. The sheets 1, 2
of the tube-plate are provided with bores 3, 4, 5 and 6
which confront each other and in which tubes 7, 8, 9 and
3Q 1~ are to be expanded to form good seals.
The sheets 1 and 2 are welded at their edge regions
to the side wall 11 of the heat-exchanger so as to be
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parallel and spaced apart from one another, and are each
provided in the region of each of the bores 3, 4, 5 and 6
with an annular, substantially cylindrical lip, as indicated
by numerals 12, 13, 14 and 153 respectively, obtained by
stamping.
The sealtight securing of the tubes 7 to 10 within
the corresponding bores 3 to 6 of ~he sheets 1 and 2 is
achieved by means of a tube expansion machine 16.
The machine 16, which is more clearly shown in
Figure 2, has a generally cylindrical body 17 which is a
housing for a fluid-operated double-acting ram, and within
which a piston 18, fitted with a sealing ring 19, divides an
active front working chamber 20 from the active rear chamber
21; the chambers 20 and 21 are in communication with a
hydraulic or pneumatic feed (not shown in the drawing) via
respective ducts 22 and 23 which are supported by a gun-
handle 24 integral with the cylindrical body 17, and the
flexible hoses 25 and 26.
The gun-handle 24 has a trigger 27 to act upon a
switch 28 of an electric or magnetic valve, a 3-way valve
not shown in the drawings, for directing the fluid feed to
one of the active chambers 20 and 21 of the double-acting ram,
and for allowing release of fluid from the other of the
chambers 20 and 21.
To a front surface 29 of the piston 18 is fastened
a rod 30 which projects beyond the body 17, a seal between
` the body 17 and rod 30 being provided by an annular gasket
31.
The rod 30 supports coaxially, on a portion beyond
the body 17, an annular plug 32 of tough rubber; the annulus
of the plug 32, as seen in longitudinal section, tapers at its
opposite end regions 33, with the actual ends being squared
off. The tapered end regions 33 are inserted into respective
annular generally V-shaped grooves 34 and 35 formed in faces,
which confront each other~ of two slightly deformab1e nylon
rings 36 and 37 idly mounted on the rod 30.
The nylon ring 36 rests with that face which is
remote from the plug 32 and which is smooth, against a face
of the body 17 and is kept in fixed position thereby, whereas
a corresponding smooth face of the nylon ring 37 rests against
a shoulder ring 38 which is made integral with the rod 30
by means of a latching ferrule 3~ screwed onto the free end
of the rod 30, the ferrule 39 pressing the shoulder ring 38
against a projection 40 of the rod 30.
The active rear chamber 21, moreover, is closed
in that portion confronting the piston 18 by an end stroke
abutment 41 for the piston 18; the abutment 41 is equipped
with a sealing gasket ~2 and a screw-threaded hub 43, with
which it can be adjusted axially so as to vary the stroke
` of the piston 18 and thus the degree of compression of the
tough rubber plug 32; the adjustment is assisted by annular
shims 44 which, slipped onto the hub 43, are held in position
by a làtching ferrule 45 which is screwed into the body 17
and to which, by a nut 46, the hub 43 of the member 41 is
locked.
The top face of the cylindrical body 17 is provided
with a supporting ring 47 which, with the aid of a counter-
weight cable (not shown), makes it possible to balanc~ the
weight of the expansion machine 16 to make its use more
convenient.
The operation of the machine 16 will now be
described.
With the two stamped sheet metal sheets 1 and
2 which make up the tube-plate correctly positioned, there is
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inserted in each of the bores 3 to 6 having the confronting
annular lips 12 to 15, the end of a tube 7, 8, 9 or 10
(see the tube 10 in Figure 1?, to be secured in a sealtight
manner, whereafter into the tube end the gunlike expansion
machine 16 is introduced (see tube 9 in Figure 1).
At this stage, by pressing and keeping pressed
the trigger 27 of the expansion machine 10, oil under pressure
is fed via hose 25 and duct 22 to the front working chamber
20 so that the piston 18 and therewith the rod 30 are urged
rapidly towards the left (as shown in the drawings).
The result is that the tough rubber plug 32 is
compressed between the nylon rings 36 and 37, which first
causes slight deformation in a radially outward direction
of the nylon rings 36 and 37 thereby tending to prevent any
extrusion of the plug 32 past the rings 36 and 37, and then
causes the plug 32 to expand radially, which in turn causes
the tube (see tube 8 in Figure 1) to expand and abut the
annular lips 12 to 15, whereby expanded areas ~, 49 and 50
are formed in the tube (best seen in tube 8 or 9 in Figure l);
the tube is permanently locked in the tube-plate as the elastic
deformation of the annular lips, such as 12 or 13, provides
an efficiently tight seal.
Then, upon releasing the trigger 27, which is biased
by a spring 51 (shown in Figure 2), the trigger is brought
back to the idle position, to allow the other active chamber
21 to receive the oil feed to cause the rod 30 to shift to
the right, thus enabling the plug 32 to take up its starting
position~
The expansion device 16 can then be removed from
the tube, with the latter left locked rigidly in a sealtight
manner in the corresponding bore of the stamped metal sheets
1, 2 (see the tube 7 in Figure 1).
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