Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a method of shaping a bell end on a
pipe of thermoplastic material, ~he opening of the bell end having a diameter -: .
which is smaller than the maximum diameter of the inner surface of the bell
end and substantially equal to the outer diameter of the pipe, by means of :
a cylindrical shaping mandril which is to be axially inserted into the pre-
heated pipe end. :
. In a method of this kind ~hich is known from our Canadian Patent
No. 963,618 which issued March 4, 1975, the shaping mandrll comprises a
base part a shaping ring of deformable material slidable on the base part
10 and a sleeve part slidable with respect to the base part, said base and ~
sleeve parts being profiled such that in the operative position of the shap- : :
ing mandril, the shaping ring is locked against axial and radial deformation
in an annular chamber formed between the base part and the sleeve part, the
outer surface of the shaping mandril having cylindrical portions of step-
like varying diameters with conical transition portions, the shaping ring
comprising at least one cylindrical portion having a diameter which is larger
, ~ than the outer diameter of the pipe, the base part and ~ the sleeve part .
. having a cylindrical portion whose diameter is substantially equal to the
o~ter diameter of the pipe, the sleeve part having a conical front portion
2~ adjoining
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the cylindrical portion t~ere1of and which is forwards
and radially inwards inclined, the smallest diameter
thereof being at the most equal to the inner diameter
of the pipe.
The bell end is then formed by relative axial
movement of the shaping mandril in said operative position,
and the pipe resulting in a step-wise expansion of the
pre-heated pipe material and by means of an external tool,
consisting for example of a pressure ring which can be
coaxially secured with respect to the shaping mandril
and a split, initially open shaping sleeve, the pressure
ring abutting against the shaping sleeve in a given relative ~
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position of shaping mandril and pipe, the shaping sleeve
being subsequently clamped about the pipe end. In order
to release the shaping mandril, first the clamping between
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the two metal mandril parts is removed, and subsequently
the base part of the shaping mandril and after that the
shaping ring and the sleeve part are axially removed from
the bell end formed. ~ -
~ 20 In the described known method, after the interior
; 3 of the bell end has been made accessible by removal of the
i base part of the shaping mandril therefrom~ the deformable
.: `~ ,o shaping ring is first removed, using a suitable tool~
from the bell end which has meanwhile cooled, and is subse~
quently slid by hand onto the base part again. After that,
t~e sleeve part of the shaping mandril is removed from the
.
~ bell end by means of a hook-like tool which can engage ~ ~
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behind the sleeve part inside the bell end and which also serves, in
the active position of the shaping mandril, for keeping the metal
mandril parts clamped together, after which the shaping mandril can
be brought into the active position again by means of said tool.
The invention has for its object to provide a method in
which the mandril parts can be removed from the formed bell end in a
completely mechanical manner, with the result that the method according
to the invention can be carried out faster.
To this end, according to the invention, there is provided
a method of shaping a bell end on a pipe of thermoplastic material the
opening of the bell end having a diameter which is smaller than the ~
~` maximum diameter of the inner surface of the bell end and substantially -
equal to the outer diameter of the pipe, by axially inserting a
cylindrical shaping mandril into a pre-heated pipe end, said mandril
comprising a base part having a diameter equal to the diameter of said
~' opening, comprising the sequen-tial steps of: radially expanding an elastic
`t shaping ring onto said base part from a relaxed state having an outside
diameter at the most equal to said base part diameter to an operative
' position having a diameter equal to said maximum diameter; res-training
said shaping ring against axial movement with respect to said base part;
moving at least one of said mandril and said pipe axially with respect
' to each other so as to insert said mandril into an end of the pipe;
causing a bell end portion of the pipe to deform inwardly so as to form
a bell end having an opening whose diameter is smaller than said maximum
diameter; cooling said pipe such that the shape formed about the mandril
! will be retained, continuing said restraining step while said moving,
deforming and cooling steps are performed; forming a space radially inward
from said shaping ring so as to establish a clearance under the shaping
ring; allowing said shaping ring to contract elastically into said
`' 30 clearance~ and lastly moving at least one o~ said mandril and said pipe
axially with respect to each other so as to remove said mandril from
said pipe end. -
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In the method according to the invention, during the relative
movement between shaping mandril and pipe for removing the mandril from
the bell end, a clearance is formed be~ween the cylindrical surface of the
base part on which the shaping ring is located when locked and the sleeve
part~ so that the shaping ring is initially arrested by the engaging part
of the bell end and slides over said surface of the base part while gradual- ~`
ly retreating into the said clearance by its elasticity.
The shaping ring is deformed to only a minor extent and only in
the radial direction. In contrast with other known methods, in which the
shaping ring is forced out of the bell end while being substantially de~
formed~ in the method according to the invention the shaping ring is sub-
jected to only minor forces, just sufficient to overcome the friction
between shaping ring and shaping mandril.
The invention also relates to a mandril assembly for shaping
a radially enlarged interior region in a tubular material, comprising a
base part~ a shaping ring~ a sleeve part and means for causing relative
movement between the said base part and said sleeve part into operative
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and removal positions~ said base part having at least a first surface having
a first diameter less than an inside diameter of said enlarged region~ and
` 20 a surface of lesser diameter than said first surface~ said shaping ring be-
ing elastically stretchable and slidably mounted for axial movement on at
least said surface of lesser diameter on said base part, said sleeve being
coaxial with said base part and having an outer diameter at the most equal
to said first diameter~ in said operative position said shaping ring being
positioned on a surface of said base part such that an outer surface of the
shaping ring has a diameter greater than said first diameter, in said
removal position said shaping
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ring being axially movable with respect to said base part into a
clearance between said surface of lesser diameter and said sleeve
part such that said shaping ring contracts elastically over said
surface of lesser diameter so as to ha~e a maximum diameter less than
said first diameter, whereb~ said mandril can be removed from the ~:
tubular material ~ithout disassembly after formation of the radially
en1sreed region.
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The invention furthermore relates to an embodiment of the ~`
apparatus in which the shaping ring is supported by a spring member.
The radial contraction of the shaping ring is thus facilitated and
durably maintained.
~ n a preferred embodiment of the apparatus according to
the invention, the spring member has a cylindrical shape and is
embedded near the inner surface of the shaping ring. The embedded
cylindrical spring member thus reinforces and supports the shaping
; ring over the entire circumference.
In a further preferred embodiment of the apparatus according
to the invention, the spring member consists of a steel wire which is
formed into a closed wave-line with constant wavelength and amplitude,
the wave crests being situated near the side edges of the shaping ring.
As a result, a uniform spring action is exerted by the spring element ~-
on the shaping ring.
i~ In another embodiment of the apparatus according to the
invention, the spring member is connected to the material of the ;
shaping ring by vulcanizing. ~
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1(~5~)221 :The invention will now be described in ~reater detail with
reference to an embodiment which is diagrammatically shown in the
drawing.
Figure 1 is a longitudinal sectional view of an embodiment
of the apparatus according to the invention which is shown at the instant
at which a bell end has been formed on a pipe, the lower half of the
apparatus having been omitted for the sake of simplicity.
Figure 2 shows a similar sectional view of the apparatus,
which is now shown in a subsequent phase of the process.
, 10 Figure 3 is a longitudinal sectional view of a portion of the
; shaping ring at an increased scale.
I Figure 4 is a longitudinal sectional view of the shaping
`~ mandril according to the line IV-IV in Figure 1.
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221
The apparatus shown in the drawing serves for shaping a bell end
2 on a pipe 1 of thermoplastic material, the inner surface of the bell end 2
locally having a diameter which is larger than the outer diameter of the pipe
1 adjoining the bell end 2 in order to accommodate a sealing ring (not shown)
at a latter stage between the bell end and a spigot to be coupled thereto.
.
e opening 3 and the rear part of the bell end, in order to fix the said
seal therein, has a diameter which is substantially equal to, that is to
- say slightly larger than~ the outer diameter of the original pipe lo
The pipe 1 is secured in a longitudinally split clamp 4 such that
its pre-heated end 2 extends therebeyond. A cylindrical shaping mandril, -
generally denoted by 5 and supported by the frame coaxially with the pipe
clamp 4, and the said clamp 4 are moved towards each other after the shaping i
mandril has been assembled in a manner to be described hereinafter, the
heated pipe end then being deformed into the bell end 2 shown while slid-
~i ing over the æhaping mandril 5. The pipe clamp 4 can be connected to the
stationary frame~ the shaping mandril then being axially movable with re-
'~ spect to the frame.
The shaping mandril 5 has a cylindrical outer surface of step-
wise varying diameter~ the transitions between neighbouring cylindri~al
surfaces of different diameter being conical. The shaping mandril 5 con-
sists of a metal base part 7 having a cylindrical surface 6 the diameter
of which is substantially equal to, that is to say slightly larger than,
the outer diameter of the pipe 1~ of a shaping ring 13 of rubber or sim-
' ilar elastic material with two c~lindrical surfaces 8, 9 the diameter of
I which is larger than the outer diameter of the pipe 1 and with conical
~ portions 10~ 11, 12 and of a metal sleeve part 15 having a cylindrical
'
'~ J surface 14 whose diameter is slightly larger than the outer diameter of
the pipe 1~ and also having a conically declined surface 16.
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The shaping ring 13 is first slid over a cylindrical surface 17,
having a diameter smaller than that of the rear surface 6~ on the base part
7 until its profiled rear edge 18 engages behinda~complementary profiled
edge 19 (Figure 2) on the base part 7, the edge 19 also serving as an abut-
ment preventing further movement of the shaping ring. The sleeve part 16
is subsequently slid over a cylindrical surface 20, having a diameter smaller
than that of the surface 17~ onto the base part until a profiled edge 2
(Figure 3) on the sleeve part engages behind the complementary profiled
front edge 22 of the shaping ring 13; in this position further sliding of
the sleeve part 15 is prevented as said sleeve part then just abuts against
a radial abutment 45 on the base part 7.
Therefore~ the shaping mandril 5 is provided with means by which
~ -prior to the relative movement of shaping mandril and pipe for shaping the
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bell end 2 thereon - the shaping ring can automatically be brought into its
operative position on the shaping mandril in an annular chamber fo~med by
the base part 7 and the sleeve part 15, in this position the shaping ring 13
-~ ~ is locked against radial deformation as well as axial def~rma*ion by the
i overlapping edge portions 18 and 19 on shaping ring and base part 7, re-
`~ spectively5 on the one side, and by the overlapping edge portions 22 and 21
on shaping ring and sleeve part 15~ respectively, on the other side; the
sleeve part 15 is then just abutting against a radial abutment 45 which is
formed between the cylindrical surfaces 17 and 20 of the base part 7 (to be
l described in detail hereinafter).
The apparatus is furthermore provided with pressure means for
keeping the sleeve part 15 pressed against the base part 7 as will be de-
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` scribed hereinafter.
When the shaping mandril 5 and the pipe clamp 4 are moved towards ~-
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~ each other~ to the position shown in Figure 1, the bell end can be pressed
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()221
in known manner, for example by means of an external tool, against the outer
surface of the shaping mandril, with the result that the inner surface of
the bell end adopts the shape of the mandril in an accurately calibrated
manner. The part of the bell end 2 adjoining the bell end opening 3 can
be pressed, for example, by means of a pressure ring 23, and the remaining
part of the bell end 2, comprising the cylindrical portions of larger diam-
eter~ can be pressed by means of a longitudinally split shaping sleeve 24
which adjoins the pressure ring 23 and which is arranged at a given distance
from the pipe clamp 4.
; 10 _ After the described step has been carried out, the shaping mandril
5 must be removed from the bell end 2 which has meanwhile cooled down suf-
ficiently; however in this position the shaping ring 13 is locked in the
bell end 2 by the bell end opening 3 which extends radially inwards as far
as the outer rear surface 6 of the base part 7
The apparatus according to the invention enables mechanical and
automatic removal of th~ shaping mandril, notably the shaping ring being
removed in a simple manner.
To this end~ the shaping mandril S is supported to be axially
movable on the frame of the apparatus by means of a cylinder 25 which is
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- 20 coaxially arranged in the prolongation of the base part 7 and which is con-
- nected thereto. A piston rod 28 of a piston 26 provided with seal 27 and
which is reciprocatable inside the cylinder 25~ extends c~ially outwards
through an opening 29 with seal 30 in the end wall of the cylinder 25
through a coa~ial bore 31 of the base part 7 and terminates in a radià1L col-
lar 32. In the position shown in Figure 1~ this collar 32 engages behind a
flange 33 which extends radially inwards on the foremost end of the sleeve
part 15 which is slidable over the surface 20 of the base part 7, thus keep-
ing the sleeve part rigidly pressed against the base part when pressure
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medium is admitted into the cylinder 25 via a port 34. The cylinder 25 and
the piston 28 which engages behind the flange 33 by way of the collar 32
thus constitutes the said pressure means for keeping the sleeve part 15
pressed against the base part 7.
In the embodiment of the apparatus shown~ the rubber shaping ring
13 is provided with a metal spring member. To this end, a steel wire 36
(see Figure ~) is embedded in the rubber material by vulcanizing near the
cylindrical inner surface 35 of the shaping r~g, the said wire having the
shape of a closed wave-line 36a with a constant amplitude, the wave crests
36b thereof being situated near the profiled edges of the shaping ring.
The dimensions of the shaping ring 13 shown at an increased scale
in Figure 3 have been chosen such that in the relaxed state of the shaping
ring its largest outer diameter is smaller than the smallest inner diameter
of the bell end formed, and thus also smaller than the largest diameter of
the metal shaping mandril portions 7, 15.
In the position of the shaping mandril shown in Figure 1, the
shaping ring 13 is in a radially expanded state and its inner surface 35
bears under tension on the cylindrical surface V of the base part 7, the
axial dimension of said surface corresponding to that of the shaping ring. -
According to the invention, the metal shaping mandril portions 7
and 15 are constructed to be complementary on their cooperating, slidably
engaging parts; the base part 7 ~see Figures 2 and 4) comprises a conically
declined surface 37 extending from said radial abutment 45 on the front end
of the cylindrical surface 17 to the cylind-rical surface 20; the said sur-
face 37 is provided with recesses 38 (see Figure 4) extending over an axial
distance larger than the axial dimension of the shaping ring 13 and as far
as the surface 20~ and with intermediate radially outwards extending ribs
39 (see àlso Figure 4); the sleeve part 15 comprises an inner cylindrical
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surface 40 slidable over the cylindrical surface 20 of the base part,
recesses 43 which extend as far as a corresponding conically declined inner
surface 41 (see Figure 2)~ and intermediate radially inwards projecting ribs
42.
The largest radial dimension of said inner conical surface 41 of
the sleeve part, which is smaller than the largest radial dimension of the
outer surface 14 thereof, terminates near the profiled edge 21 in a radially
interrupted abutment 44 which is formed by the edges of the ribs 42 and
which cooperates with the said radial abutment 45 on the base part which is
interrupted by the end edges of the groove-like recesses 43 and which serves ~
to limit the sliding movement of the sleeve part over the base part. - -
In order to enable removal of the shaping mandril 5 from the bell
end 2 formed (see Figure 2), first pressure medium is admitted into the
cylinder 25 via a ~ort 46, with the result that the piston 26, and hence
~l the collar 32 on the piston rod, moves away from the flange 33 on the
:! sleeve part, the clamping action between the shaping mandril portions 7, 15
~` and also the locking of the shaping ring 13 then being removed. The support
of the cylinder 25 on the frame of the apparatus is then moved away from
the clamping sleeve 4 together with the pressure ring 23 and the base part
7. The shaping ring~ arrested by the opening 3 of the bell end formed and
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sl~ding over the surface 17 and the sleeve part 15 sliding over the surface
20 of the base part 7 remain within the bell end, a clearance being formed
¦ between the ribs 39 and 42 of the metal shaping portions 7 and 15 in which
the shaping ring can retreat under radial contraction while sliding with its
inner surface 35 over the conical outer surface 37 of the ribs 39, the shap-
ing ring then assumes a smaller radial outer dimension until it is completely
situated within the outer cylindrical surfaces 6 and 14 of the base part 7
and the sleeve part 15~ respectively. Subsequently~ by a further m~vement
13
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of the cylinder 25, the sleeve part 15 and the shaping ring 13 are also
displaced~ via the collar 32 on the piston rod 28~ so that they are complet-
ely removed from the bell end. The shaping sleeve 24 is then fold~d open,
like the pipe clamp 4, after which the pipe with bell end can be removed.
The cylinder 25, together with the shaping mandril 5 and the --
pressure ring 23, is returned to the axial starting position. After that,
the shaping ring is secured on the shaping mandril again by admitting pres-
sure medium into the cylinder 25 via the port 34, with the result that the
sleeve part 15, taken along by the collar 32 on the piston rod 28, abuts
with its abutment face 44 against the front edge 22 of the shaping ring 13,
thus pushing this ring along the conical outer surface 37 of the ribs 39
onto the base part 7; the shaping ring is locked in p~a~e again~ in the
axial and the radial direction and under radial expansion on the surface
17 of the base member 7.
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