Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Expanding Tool for Cold Forming
Technical Field
The present invention relates to an expanding tool for
temporary expansion of tube ends made of cross-linked
polyolefin, consisting of a generally cylindrically shaped
expanding mandrel which is provided with an at least
partially conically shaped inner bore and which is
subdivided in axial direction into a multiple number of
expanding members substantially having the shape of a
cylindrical sector, further consisting of respective
holding members protruding from the outer circumference of
the expanding members, biassing means acting upon the
holding members for biassing the expanding members into
mutual engagement in order to form the generally
cylindrically shaped expanding mandrel, recesses extending
along the circumference in the expanding members
intermediate rounded free ends and the holding members, a
housing within which the holding members are radially
displaceably guided, conically shaped expanding means for
engaging the at least partially conically shaped inner bore
of the expanding mandrel, and actuating means for
reversibly axially displacing the expanding means within
the inner bore of the expanding mandrel and expanding the
same against the force of the biassing means.
Background Art
Such expanding tool is known from International Published
Patent Application No. WO 9418486 and serves for reversibly
expanding tube ends which are made of cross-linked
polyolefin and provided with a clamping ring; after
expansion, the tube ends are pushed onto a connector having
a connecting member which is provided with an external
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flange. The tube end thus expanded at ambient temperature,
after being pushed onto the connecting member, is subject
to self-reconversion at ambient temperature resulting in a
firm and sealing connection.
The expanding tool includes a generally cylindrically
shaped expanding mandrel which is subdivided into a number
of expanding members and defines a conically shaped inner
bore into which a piston can be advanced which is
mechanically, electrically or pressure fluid driven and has
a correspondingly conically tapering end. The piston is
arranged within a housing having an end wall at which the
expanding members are located. Each expanding member has a
rounded front end; a recess is formed in its circumference
at a spacing from the front end. A radial member is located
at the rear end of each expanding member and extends
between housing covers which are screwed onto the front end
of the housing and between which the expanding members are
radially displaceably guided. In the inoperative condition,
the expanding members are held together by means of an
annular spring which acts upon the circumference of the
radial members.
For reversibly expanding the tube end, the rounded end of
the expanding members is first inserted into the tube end.
The expansion is, then, effected by advancing the piston
into the conically shaped inner bore of the expanding
mandrel and is defined by engagement surfaces at the
expanding members. The expanding members are forced apart
against the force of the annular spring. After the thus
effected expansion, the piston is withdrawn and the
expanding members are returned into their starting position
under the action of the annular spring. During this
expansion, the circumferential edges of the forced-apart
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expanding members engage the inner wall of the tube end to
be expanded whereby notches arise in the inner wall of the
tube and may result in leaks. In the region of the recesses
of the expanding members, the inner wall of the tube does
not contact the bottom of the recesses. The notches caused
by the circumferential edges of the expanding members,
therefore, are not formed in the region of the recesses.
The recesses are dimensioned such that their axial width
exceeds the axial width of the external flange at the
connecting member of the connector so that the connection
to the connecting member is produced in a region which is
free of the notches.
From U.S. Patent No. 3,385,087, there is known an
expanding tool for expanding tube ends, for example, the
ends of exhaust pipes. Such tool includes an expanding
mandrel which is actuated by means of a double acting,
pressure fluid operated piston. The expanding mandrel
extends generally conically into expanding members which
define a conically shaped inner bore in the inoperative
condition. At their outer side, the expanding members have
a circumferential groove into which an O-ring is inlaid
which is made of, for example, rubber and serves to hold
the expanding members in place. After pushing on the tube
end, the expanding mandrel is actuated in order to force
apart the expanding members and thereby expand the pushed-
on tube end. After the expanding operation, the piston is
withdrawn so that the expanding members can return into the
inoperative position. The tube end is expanded due to
plastic deformation and preserves its expanded dimension.
A further, similar expanding tool according to German
Published Patent Application No. 42207g4 for expanding the
tube ends of reversibly deformable plastic tubes includes
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expanding members without recesses at their circumference.
An expanding tool according to European Published Patent
Application No. 0619152 includes a clamping cap which is
connected to the expanding members by means of specifically
constructed connecting and guiding means.
Furthermore, there is known from German Published Patent
Application No. 3817442 as well as German Utility Model No.
9404513 a connector comprising at least one connecting
member for connection to a reversibly expanded tube end.
For firm and sealing connection to the tube end, the
connecting member is provided with at least one holding
element defining an outer surface which gradually slopes
towards the free end of the holding member, and a surface
which steeply slopes towards the opposite side. The
gradually sloping outer surface facilitates pushing-on the
expanded tube end while the steeply sloped surface
conjointly with the gradually sloping outer surface defines
a sealing edge which is of significance for forming a firm
and sealing connection.
The initially mentioned expanding tool, due to the
recesses at the outer circumference of the expanding
members, does prevent the formation of notches in the inner
wall of the tube end by means of the edges of the expanding
members in the region of the recesses during expansion. A
sufficient depth of the recesses is therefore required.
However, due to the gaps formed between the forced-apart
expanding members and the recesses, circumferential ribs
arise at the inner wall and protrude into the interior of
the expanded tube end to such extent as to significantly
impede the pushing-on operation of the tube end after
removal of the expanding mandrel.
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Disclosure of the Invention
Accordingly, it is the object of the invention to provide
an expanding tool of the initially mentioned type which
ensures firm and sealing engagement of the expanded tube
end to the particular connecting member and which does not
adversely affect the connecting operation.
In accordance with the invention, this object is achieved
in that a ring, which is made of a material having a self-
reconversion behavior comparable to that of cross-linked
polyolefin, is received in the recesses.
In the presence of the ring there is formed a uniformly
deformed region at the inner wall of the expanded tube end
in the area of the recesses and between the expanding
members and this region protrudes less into the interior as
in the case of the absence of the ring. The pushing-on
operation of the tube end onto the connecting member is
facilitated thereby. Additionally, the self-reconvertible
ring has the advantage of contributing to better holding
together the expanding members and providing for the
expanding members an additional restoring force in addition
to that of the annular spring after withdrawal of the
expanding cone.
It is particularly advantageous using an expanding tool
in conjunction with connectors having connecting members
which comprise the aforementioned holding elements
including a sealing edge and wherein the recesses and rings
at the expanding members are aligned to this sealing edge.
Specifically, the recesses at the expanding members may be
axially arranged in a manner such that the sealing edge at
the holding element is disposed symmetrically relative to
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the recesses. If desired, there may be provided more than
one recess at the expanding mandrel and more than one
sealing edge at the connecting member.
In such construction of the expanding mandrel, a tube end
region, when compared to the absence of the ring, is less
but uniformly expanded and extends in circumferentially
closed manner around its inner wall. This region
experiences a small expansion and self-reconversion which
does not impede the pushing-on operation during passage
over the sealing edge of the connecting member. It is
thereby ensured that, notwithstanding the gaps which arise
between the expanding members during the expanding
operation, at least this region of the tube end comes to
firmly and sealingly engage the connecting member on both
sides of the sealing edge around its entire inner
circumference whereby a firm and sealing connection is
formed in toto.
Brief Description of the Drawings
Exemplary embodiments of the inventive expanding tool are
illustrated in the drawings and will be explained and
described in detail hereinbelow having regard to the
reference characters. There are shown in
Figure 1 a longitudinal section through an exemplary
embodiment of the expanding tool according to the
invention;
Figure 2 a cross-section through the expanding tool as
shown in Figure 1 along the line II-II;
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Figure 3 a longitudinal section through a detail of Figure
l;
Figure 4 a longitudinal section through a modified
5construction of the expanding tool as shown in
Figure 1; and
Figure 5 a view of a connector for use in conjunction with
the expanding tool as shown in Figure 1 or Figure
4.
Preferred Embodiments of the Invention
Figure 1 shows a longitudinal section through a first
exemplary embodiment of an expanding tool including a
housing 1 which contains at one end thereof actuating means
2 for actuating the expanding tool. In the illustrated
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exemplary embodiment the actuating means 2 comprise a
pressure fluid operated piston 3 which is connected to
expanding means in the form of an expanding cone 4 by means
of, for example, a screw connection. Instead of the
pressure fluid operated piston 3 there may also be provided
different actuating means like, for example, mechanical
actuating means. The pressure fluid may be axially or
radially fed to the housing 1. The housing 1 may be
provided with holding means permitting the housing to be
held during operation; the housing is constructed such as
to also permit overhead work.
At the opposite end of the housing 1 there is arranged a
generally cylindrically shaped expanding mandrel 5. This
expanding mandrel 5 contains an inner bore 6 comprising a
conically shaped bore portion 7, which is engaged or can be
brought into engagement with the expanding mandrel 4, and a
cylindrical bore portion 8 in the free end thereof. At this
free end, the expanding mandrel 5 is provided with a
chamfer 9 which may extend at an angle in the range of 5~
to 20~ relative to the circumferential surface of the
expanding mandrel 5. The edges which delimit the chamfer 9,
are rounded. The chamfer 9 as well as its rounded edges
prevent damages to the inner wall of the a tube end 19 into
which the expanding mandrel 5 is inserted for expansion.
The expanding mandrel 5 is multiply subdivided in
lengthwise direction and comprises a number of expanding
members 10 which assume the shape of cylinder sectors; in
the illustrated exemplary embodiment, see Figure 2, the
expanding mandrel 5 is subdivided eightfold and thus
comprises eight expanding members 10. In the inoperative or
non-actuated condition of the expanding mandrel 1, the
expanding members 10 engage each other in circumferential
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direction and thus define a generally cylindrical
circumferential surface.
A thickened section 11 is formed at the inner end of the
expanding mandrel 5 or at the inner ends of the expanding
members 10, respectively. Holding members extend therefrom
and thereby the expanding mandrel 5 is exchangeably held in
the associated end of the housing 1. In detail, each one of
the holding members comprises an arm 12 which radially
projects from the circumference of the thickened section 11
and which is provided at its circumference with an
accommodation 13 for receiving biassing means such as, for
example, an annular spring 14. The annular spring exerts a
radially inwardly directed bias on the expanding members 10
whereby the expanding members 10 are held in mutual
engagement in the non-actuated condition of the expanding
mandrel 5 and whereby the generally cylindrical
circumferential surface of the expanding mandrel 5 is
formed. The radially projecting arms 12 are radially
displaceably placed in guide means at the associated end
wall of the housing 1 and such guide means comprise a
holding plate 15 and a bearing plate 16 provided with a
slide element 17. The holding plate 15 is releasably
mounted at the end wall of the housing by means of screws
so that the expanding members 10 or the expanding mandrel
5, respectively, are exchangeably arranged at the end wall
of the housing 1 by means of the radial arms 12 and the
holding plate 15.
Respective recesses 18 are located at the expanding
members 10 intermediate the thickened section 11 and the
chamfer 9 and constructed such as to form a circumferential
groove in the closed or non-actuated state of the expanding
mandrel 5. Preferably, the edges of the recesses 18 are
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bevelled in order to avoid damages to the tube end 19 upon
insertion of the expanding mandrel 5.
The longitudinally sectional illustration of Figure 3
shows in detail the expanding mandrel 5 and a ring 28 which
is inlaid into the recesses 18. This ring completely or
partially fills the recesses 18. It is made of an elastic
material or a material which is self-reconvertible at
ambient temperature and which, if desired, may be
reinforced. Preferably, it is made of a material having a
self-reconversion behavior which is comparable to that of
the expanded tube end and likewise may consist of cross-
linked polyolefin.
In this as well as the exemplary embodiment described
hereinbelow, the members such as the expanding cone and the
expanding members of the expanding mandrel which are
subjected to high mechanical stress, are manufactured from
high-order tool steel. There is thus prevented, on the one
hand, the formation of frictions and seizures between the
parts which act upon each other, and deformation of the
expanding members under the action of high expanding
forces, on the other hand.
In the upper half of Figure 1 the expanding tool is shown
in the inoperative condition. In this condition, the
expanding mandrel 5 merely is placed within the conically
shaped bore portion 7 of the inner bore 6 of the expanding
mandrel 5 and there is no axially directed force which acts
upon the expanding cone 4. The expanding members 10 are,
then, in mutual engagement and the expanding mandrel 5
forms a generally cylindrical body as shown in Figure 2.
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Upon applying pressure to the piston 3, this piston and
therewith the expanding cone 4 are displaced within the
housing 1 towards the expanding mandrel 5. The expanding
cone 4 is thereby forced into the conically shaped bore
portion 7 whereby the expanding members 10 are urged apart
in radial direction against the force of the annular spring
14. The lower half of Figure 1 shows the expanding cone 4
in the terminal position of its displacement path in which
position the maximum expansion of the expanding mandrel 5
is achieved. During this expansion, the gaps which arise
between the expanding members 10, are bridged by the ring
28 which is received within the recesses 18 of the
expanding members 10 and which is expanded conjointly
therewith.
For expansion of a tube end, the expanding mandrel 5 is
inserted, in the inoperative condition of the expanding
tool, into a tube end 19 of a material which preferably is
self-reconvertible at ambient temperature such as, for
example, cross-linked polyolefin. During such insertion,
the end wall of the tube end 19 engages the thickened
section 11 and thereby the axial length of the to-be-
expanded tube end 19 is delimited. Upon actuating the
expanding cone 4, the expanding members 10 are outwardly
urged against the force of the annular spring 14 whereby
the tube end 19 is expanded by a corresponding amount.
During this operation, the inner surface of the tube end 19
engages the outer surface of the expanding mandrel 5,
however, not entirely in the region of the ring 28, which
is received in the recesses 18 and bridges the gaps between
the forced-apart expanding members 10. In correspondence
therewith, there is formed at the inner wall of the
expanded tube end 19 a section or land which extends in
circumferential direction, which protrudes inwardly and
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which has a height determined by the depth of the recesses
18, the thickness of the ring 28 and the extension of the
expanded ring 28 in the region between the expanding
members 5.
The significance of the ring 28 and the land formed
thereby at the inner wall of the expanded tube end 19 will
be recognized in view of the connector to which the
expanded tube end 19 is connected by means of its self-
reconversion. Such connector may be constructed, forexample, like the tube connector according to German
Utility Model No. G9404513 and is illustrated in
longitudinal section in Figure 5. The tube connector 20
defines a straight piece of tubing comprising connecting
members 21 at its opposite ends. Each one of the connecting
members 21 includes a holding element 22 for connection to
an expanded tube end like the tube end 19. Each one of the
holding elements 22 includes an outer surface 23 which
gradually slopes towards the free end of the tube connector
21 and a sealing edge 24 which steeply slopes on the other
side.
The recesses 18 of the expanding members 10 are aligned
to the axial position of the sealing edge 24 at the
connecting member 21 onto which the expanded tube end 19 is
placed. Preferably, the sealing edge 24 is symmetrically
disposed relative to the recesses 18 such that the lands,
which remain at the circumference of the inner wall at the
tube end 19 after expansion, also extend symmetrically
relative to the sealing edge 24 in axial direction. These
lands protrude inwardly to an extent less than in the
absence of the ring 28 and thereby facilitate the pushing-
on operation of the expanded tube end 19 onto the
connecting member 21 across the sealing edge 24. Otherwise,
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however, the lands are also subject to a likewise
reversible deformation for a short period of time. As a
consequence, these lands will engage, after self-
reconversion, the connecting member 21 on both sides of the
5 sealing edge 24 around its entire circumference whereby a
firm and sealing connection between the tube end 19 and the
connecting member 21 is obtained at least in this region.
Additionally, the ring 28 represents part of the biassing
means since the presence of the ring 28 has the effect of
10 holding together the expanding members 10 of the expanding
mandrel 5 and subjecting the same to a further restoring
force in addition to that of the annular spring 14 after
withdrawal of the expanding cone 4.
The connecting member 21 of the tube connector 20, if
desired, may comprise more than one sealing edge 24; in
such case, there are present more than one recess 18 at
corresponding locations of the expanding mandrel 5.
Figure 4 is an illustration which corresponds to Figure 1
and shows a modified construction of the expanding tool.
Identical parts therein are denoted by the same reference
characters. There will be recognized therein the housing 1
containing the actuating means 2 in the form of a pressure
fluid operated piston 3 which cooperates with an expanding
cone 4.
An expanding mandrel 25 includes an inner bore 26 which
is of conical configuration throughout and extends along
the entire axial length of the expanding mandrel 25.
Otherwise, also here the expanding mandrel 25 is composed
of eight expanding members which are held together under
the bias of an annular spring 14. The annular spring 14 is
held in an accommodation 13 of radial arms 12 which extend
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from a thickened .section 11 at the inner end of the
expanding mandrel 25 and which are radially displaceably
arranged at the end wall of the housing 1 between a holding
plate 15 and a bearing plate 16 having a slide element 17.
The rounded edge of the expanding mandrel 25 is connected
by means of a chamfer 9 to the remaining part of the
expanding mandrel 25; at least one recess 18 is located
intermediate the chamfer 9 and the thickened section 11 of
the expanding members 10 and a ring 28 (not shown) is
inlaid thereinto in correspondence with the showing of
Figure 3. The function and mode of operation of this
expanding tool correspond to those which have been
described hereinabove with reference to Figures 1 to 3.
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