Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention ralates to apparatus having a
travelling mold tunnel for the production of seamless -~
plastic tubing, especially single or double-walled
corrugated tubing or ribbed tubing.
Apparatus of utilizing a travelling mold
tunnel is commonly used for the production of
continuous plastic tubing. The mold tunnel is formed
between a pair of complementary mold assemblies each
of which comprises an endless run of mold blocks which
are articulately interconnected. Each mold block of
one mold assembly is complementary to a respective
mold block of the other mold assembly, the mold blocks
cooperating in pairs along the forward run to orm an
axially extending mold tunnel defining a tubular
mold. The wall of the mold is dependenk on the inner
face of the mold blocks and is the matter of choice.
The mold assemblies are driven in
synchronism with one another so that the mold blocks
circulate along the endless tracks. The mold blocks
are always located similarly with respect to the
direction of their movement. Thus when the direction
o movement changes, the orientation of the mold
blocks changes with it. For example, the mold blocks
on the retùrn run are totaled 90 with respect to mold
blocks on the tunnel run. The entrance to the tunnel
may be located suitably with respect to an extrusion
nozzle for extruding an annular parison of plastic
against the mold surface of the tunnel. When the
resuIting tube is required to have more than one wall,
the extrusion nozzle will extrude coaxial parisons of
plastic extrudate.
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Such apparatus is described in U.S. patent
No. 3,981,663 to Lupke, issued September 21, 1976 and
U.S. patent No. 3,832,429 to Charpentier 1974. These
patents describe apparatus in which the mold
assemblies are arranged one above the other. Other
conventional apparatus in use is described, for
example in U.S. patent Nos. 3,677,676 to Hegler 1972,
and 3,751,541 to Hegler 1973. The apparatus of these
patents shows the mold assemblies arranged
side-by--side. Both these conventional configurations
of apparatus have particular problems associated with
them, in that the independent mold assemblies must be
carefully synchronized in operation so that the pairs
of cooperating mold blocks come together precisely to
form the mold tunnel. Moreover, to provide a pair of
independent mold assemblies requires considerable
dup]ication of machinery and equipment and, in the
case of the side-by-side layout, the apparatus covers
an appreciable area of floor space ~hich may be an
appreciable consideration where space is limited or
expensive.
Any services which must be supplied to the
mold blocks must be provided in ~uplicate for each
mold assembly. Such services include the provision of
suction lines, hydraulic ~luid lines, possibly heating
or cooling services, etc., maintenance and repair work
is also duplicated for the mechanism of each endless
track. U.S. Patent No. 4,439,130 issued March 27th,
1984 to Dickhut discloses the use of mold blocks which
are hinged together and closed to form the mold tunnel
and opened to release formed pairs of tube. This
makes possible for a single conveyor but the mold
blocks still change orientation with changes in their
direction o~ travel.
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Since the 1970's various improvements and
modifications have been made to the basic type
apparatus disclosed in the patents referred to but
except for the manufacture of helically corrugated
tube no other basic type of apparatus is known. For
the production of helically corrugated pipe, a ribbon
of molten thermoplastic has been wound on an advancing
mandrel. It is not with this type of apparatus that
the present invention is concerned.
.
According to the invention, apparatus for
continuous molding of thermoplastic extrudate e.g.
tube, in a travelling mold tunnel to form an elongate
molding, comprises; a travelling tunnel mold assembly
of adjacent mold blocks each mold block having a bore
therethrough, the bores of adjacent mold blocks being
aligned axially; each mold block comprising a pair
pivotally connected parts whereby the parts are
movable between a closed position of the block in
which the bore is circumferentially enclosed, and an
open position in which the parts are located with
respect to each other to release elongate molding
formed between them, a tunnel conveyor ~or the tunnel
mold assembly to convey it horizontally and axially in
a molding run between tunnel entrance and a t~nnel
exit; means to open each mold ~lock as it reaches the
tunnel exit; a removal conveyor arranged to move
generally in the plane of the tunnel conveyor to
receive and convey each opened mold block sequentially
from the tunnel conveyor, each mold block being
orientated with its bore parallel to the mold tunnel;
a return conveyor generally in the plane of the tunnel
conveyor arranged to move hori~ontally parallel and
opposite to the tunnel conveyor to receive and convey
mold blocks sequentially from the removal conveyor,
each mold block being orientated with its bore
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parallel to the mold tunnel; and an approach conve~or
arranged to move horizontally and parallel to the
removal conveyor, to convey mold blocks sequentially
from the return conveyor, each mold block being
orientated with its bore parallel to the mold tunnel;
and means to close the returned mold blocks to form
the mold tunnel. The invention is ~nvisaged for use
in the molding of semi-rigid plastic tube of the type
used for underground drainage or for carrying
electrical wiring. The cross-section of such tube is
generally circular. For easy exchange of mold blocks
for ones of different diameter, each mold block may be
releasably carried on a mold block carrier of
articulately interconnected mold block carriers.
Means may be provided to maintain the mold blocks
closed on the tunnel conveyor. Such means may
suitably be either guide fences to prevent the mold
block parts pivoting awa~ from each other or a cam
actuated latches between the mold parts.
When the cam actuated latch is provided, the
latching cam may be located at the upstream end of the
tunnel to engage a first cam surface of the latch to
move it into a latching position as the respective
mold block is conveyed on the tunnel conveyor past the
cam, and an unlatching cam ma~ be located at the
downstream end of the tunnel to engage a second cam
surface of the latch to move it into a latching
position as the respective mold block is conveyed or
the tunnel conveyor past the cam. In effect, such a
latch may be a toggle latch. ~nce the hinged parts of
the mold blocks are unlatched, the mold blocks must
physically open to release tube formed in the mold
tunnel. This may be achieved through mold block
opening cam means provided at the downstream end of
the tunnel, adapted to interact with a cam surface of
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one mold block part to pivot it with respect to the
other mold block part to release the tube. Once~ the
tube has been released, the mold blocks may travel on
the removal return and approach conveyors, in either
open or closed condition. However, since the mold
blocks must open to receive an extrusion nozzle into ~ ~-
the tunnel, it~is convenient to maintain the mold
blocks open on the removal, return and approach
conveyors. At the upstream end of the tunnel, mold
blocks pivotally close under gravity. Preferably,
such closing is in a controlled manner and mold block
closing cam means may be provided to interact with a
cam surface of each mold block to close it as it moves
into position as part of the mold tunnel.
A change of direction is involved between
different conveyors and guide means may be provided to
guide the mold blocks from one conveyor to the next.
Such guide means may comprise a curved guide rails at
outer corners between each conveyor.
The hinging of the mold block parts may be
by any convenient arrangement. However, two such
arrangements, referred to as e~emplary, are
envisaged. In both arrangement, the hinge is provided
near the top of the mold block, but in one case it is
right at the top, and, in the other case, it is offset
from the top. In each case, one fixed part of each
pair of mold block parts is, in use, attached at its
base to its respective mold block carrier. In the
case where the hinge is at the top of the mold block,
abutting faces of the block of the fixed and movable
parts distant from the hinge, lie in a plane oblique
to the radius of the bore. By this means it is
possible to attach the fixed part over a stable base
area. Moreovsr, connection between the fixed and
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movable parts on the outside of the mold block may be
offset from the direct bottom, thus allowing access to
latching means. In the case where the hinge is offset
from the top of the mold block, the fixed and movable
parts may be symmetric. The face abutting faces may
be radial and offset from the bottom of the mold block
diametrically opposite the hinge. When this is so, it
may be necessary to lower the mold block slightly to
release tube from the slightly upstanding edge of the
fixed mold block. This may be achieved by making the
conveyor run descend slightly. In this case, means
are provided to lower the mold blocks on the tunnel
conveyor to release formed tube from the face of the
fixed mold part offset from the base. In any case, it
may be convenient to provide ramps between conveyors.
The invention also provides a method for
forming tube in a travelling mold tunnel comprising;
extruding parison of thermoplastic extrudate into a
travelling tunnel mold assembly wherein each tunnel
segment comprises a mold block having a bore
therethrough, the bores of adjacent mold blocks being
aligned axially; each mold block comprising a pair of
pivotally connected parts whereby the parts are
movable between a closed position of the block in
which the bore is circumferentially enclosed, and an
open position in which the parts are located, with
respect to each other, to release ~ube formed between
them; a conveying tunnel mold assembly to convey it
horizontally and axially in a molding run from between
a tunnel entrance and a tunnel exit; opening each mold
block as it reaches the tunnel exit; returning each
mold block from the tunnel exit to the tunnel entrance
upstream of the tunnel return path oriented to be
added to the tunnel entrance; and closing the returned
mold blocks to form the mold tunnel.
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Embodiments of the invention will now be
described by way of examplP with reference to the
drawings in which:
Figure 1 is a perspective view of an
embodiment of apparatus according
to the invention;
Figure 2 shows a plan view of the general
layout for another embodiment
apparatus of the invention;
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Figure 3 is an enlarged view showing one
example of a mold block and
carrier which may be used with
apparatus according to the ~:
invention, for example as
illustrated in Figure l;
Figure 4 is a cross section of the mold ~.
block and carrier of Figure 3 in
its closed position;
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Figure 5 is a similar cross section of the
mold block of Figure 4 i.n the open
position;
Figure 6 is a cross section through another
mold block and carrier in the
closed position and suitable for
use with apparatus as illustrated
in Figure l;
Figure 7 is a cross section through the
block of Figure 6 in the open
position;
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Figure 8 is a view of carriers, suitable
for use in apparatus as
illustrated in Figure 2;
Figure 9 is a view of another closed mold
block in combination with a
carrier as shown in Figure 8
indicating mold opening and
closing mechanism; and
Figure lO is a view of the mold block of
Figure 9 in the open position.
In the drawings, Figure l shows a general
view of apparatus embodying the invention which may
comprise a tunnel conveyor 12 along which travels a
tunnel mold assembly 14, segments of which are hinged ~;
mold blocks 16 of which are closed in the tunnel mold
assembly over the majority of tunnel run of a conveyor
12. Each mold block 16 comprises a fi~ed half 13 and
a hinged half 15 and each has a carrier block 17 which
may be driven to move along the conveyor 12 in a
rnanner to be described hereafter. At an upstream and
of the tunnel assembly 14, an extrusion nozzle 18
enters the tunnel to extrude an annular parison l9 of
thermoplastic material to form tube 20 within the
tunnel. At the downstream end of the tunnel assembly,
tube 20 emerges from the tunnel. Also at the
downstream end of the tunnel, mold blocks 16 open
hingeably to release tube 20 and are returned to the
upstream end of the tunnel conveyor 12 by means of a
removal conveyor 22, a return conveyor 24 and an
approach conveyor 26. Conveniently, the tunnel
conveyor 12 and the removal conveyor 22, the return
conveyor 24 and the approach conveyor 26 are laid out
in the general form of a rectangle, the upper runs of
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each conveyor being at least generally in the same
horizontal plane. While the speeds of the various
conveyors may be coordinated to return mold blocks to
the tunnel conveyor at a suitable speed to form the
tunnel assembl~ 14 on the tunnel conveyor, in a
practical embodiment the tunnel conveyor comprises a
stationary track along which the mold bloc~s 16 are j
driven via their carriers 17. i~
On the removal, return and approach
conveyors 22, 2~ and 26 the mold blocks may travel in
either an open or closed condition. However, since
the mold blocks must open to release tube 20, and must
ba open in order to close around extrusion nozzle 18,
it may normally be convenient for them to travel on at
least most of the route back to the upstream end of
the tunnel conveyor 12 in the open condition. Mold
blocks halves may open as much as 180 to each other
or even more. However, it is normally convenient that
they onl~ open widely enough to release tube 20 from
between them.
When assembled into mold tunnel assembly 1
on tunnel conveyor 12, it is important that the mold
blocks 16 have upstream faces and downstream faces ll
in contact with one another to form a closed tunnel in
the longitudinal direction. It may normally be
sufficient to press the mold blocks ~irmly togethe~ on
this run but it may be advantageous to mechanically
link the carriers, as for instance, by the illustrated
tongue 100 and groove 102 connections between them as
seen ~rom Figure 8. The halves 13, 15 of each mold
block 16 must, on the tunnel run tightly closed about
the hinge 28 so that the tunnel is also tightly closed
around its circumference, and must reliably open to
release tube 20. This may be achieved by various
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means, for example the cam arrangemen-t 50, 5a shown in
Figure 1 or the mechanism 104 shown in Figures 9 and
10 .
The alignment of the mold blocks 16 on the
tunnel conveyor 12 is also important so that the
extrusion nozzle 18 is accurately centered in the
tunnel ~or accuracy in molding the tube 20.
Conveniently, a track 30 is provided on tunnel
conveyor 12 for engagement with a corresponding part
31 of each carrier 17 for guidance and location of
mold block 16. The track 30 may be in the form of an
upstanding rail to cooperate with a groove 31 shaped
slot 31 o each mold block. The rail 30 may house a
source of suction and suction passages 33 through
carrier 17 may connect suction ports 35 o the rail 30
with suction passages 37 in the mold block 16 leading
to its interior. The provision of suction to the
interior of the tunnèl may be provided in a similar
manner to that described in any of U.S. patent
No. 4,319,872 or Canadian patent No. 1,083,765, these
patents are directed to a travelling mold comprising
mold blocks through which suction may be applied, ,
although all of the patents are limited to the use of
two conveyor systems, one for each of two runs of half
mold blocks. Nevertheless, th~ provisions of suction
means within guides for the mold blocks may be
regarded as similar.
Suitably the carriers 17 "wrap around" the
track 30 at its edges, or around an additional edge
tracks 39, by means of an inwardly extending flange
41, to prevent accidental disengagement of the
carriers 17 and blocks 16. The length o the tunnel
conveyor and the length of the tunnel assembly 14
should be suficient for extruded annular
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thermoplastic parison to set into tube 20 of
sufficient rigidity or th~ removal of mold blocks 16
without permanent distortion of the tube. Cooling
plugs, and other forming means for the inside surface
of the tube may be provided in a conventi-onal manner
supported on an inner core extending coaxially from
the extrusion nozzle. For simplicity, such devices
are not illustrated. However, additional cooling
means is possible on the outer surface of the mold, as
for example, by ribs 106 on its outer surface as shown
in Figure 9. Cooling water may be flowed over the
exterior of the closed mold tunnel assembly to aid
cooling and drain channels 108 may be provided for the
water.
When the mold assembly has remained closed
over a sufficient length ~or the tube to set, the mold
blocks may be opened by hinging each of them about its
hinge 28. Once open, the blocks may be removed from
the tube, for example, orthogonally therefrom along
removal conveyor 22. While, as already commented, the
speeds of the various conveyors should be coordinated,
there is no particular reason for accurate alignment
of the mold blocks 16 in tunnel formation on any of
the removal conveyor 22, the return conveyor or the
approach conveyor.
In practice, it is convenient that removal
conveyor 22 runs at an angle of slightly more than 90
to the tunnel conveyor and that mol~ blocks are
located on it with their tunnel axis not quite aligned
with the directional axis of conveyor 22. Thus, the
orientation of mold blocks 16 is the same as on tunnel
conveyor 12 so that they are set at a slight angle on
conveyor 22. On tunnel 12 mold blocks 16 more in the
direction of the tunnel axis. Whereas, on conveyor ~7
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they move in a direction at slightly greater than 90
to the tunnel axis of each block 16.
It is convenient to remove the mold blocks
16 in a direction parallel with the upstream faces and
the downstream faces 17 and, although sufficient
guidance means should be provided to prevent them
falling off the conveyor, there is no need for
accurate guide means such as track 30. The guidance
means may conveniently ~e chains 110. The provision
of a guide rail 32 extending alongside removal
conveyor 22 and, at least partially, alongside tunnel
conveyor 12 may be useful in some instances.
When a tongue 100 and groove 102 linkage is
provided between mold blocks carriers 17 (See
Figure 8) on the tunnel run, this linkage must be
disconnected to allow the carriers 17 with their
associated blocks 16 to travel essentially edge to
edge on the removal run rather than face to face.
The linkage may comprise a rail of T-shaped
cross section or, as illustrated an aligned pair of
lugs 100 o~ T-shaped cross section on one tunnel face
of a carrier, e.g. the downstream face 11 and a
corresponding T-shaped groove 102 in the other face.
When travelling in the tunnel direction the T-groove
102 interlocks the T-rail 100 to hold faces of
ad~acent blocks in register. However, when a block 16
and its associated carrier 17 are subjected to an
approximate gO change of direction without change of
orientation, as indicated, for example, by the arrow A
in Figure 8, (or in the 180 direction), then
T-members 100 will slide out of T-grooves 102 to
unlatch the carriers and allow them to move away in
the new direction.
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~ rhe movement of carriers 17 ~and hence
blocks 16) on the tunnel conveyor may be by means of
driven sprocket wheels 32 which mesh with lugs 112
provided on one, or as illustrated both, sides of
carriers 17. Such sprocket wheels 32 at the upstream
of the tunnel run may conveniently drive the entire
tunnel train of carriers 17 and mold blocks 16.
Movement of the carriers and mold blocks on
removal 22, return 24, and approach 26 conveyors may
be by any convenient means. However, it is to be
noted that similar sprocket wheels may be used on the
return run and chains 110 which may run on sprocket
wheels 114 driven in any convenient manner. For
additional ease in transition from one direction to
another, where one conveyor adjoins another conveyor
travelling in a different direction, ramps may be
provided in the conveyors.
Even when the apparatus is used for molding
pipe of small diameter, the thickness between its
faces is usually considerably less than the width of ~ -
the block across the horizontal diameter of the mold
tunnel. In fact, the apparatus is suitable for the
molding of large diameter tube and, for mold blocks
for molding large diameter tube, the difference
between the thickn0ss of the block and the width of
the block is considerable.
Since the blocks move in the direction of
their thickness on the closed mold tunnel run on
tunnel conveyor 12 and in the general direction of
their width on the removal and approach conve~ors 22,
26, it is clear that the speed of conveyors 22 and 26
will be greater than that of the mold blocks on tunnel
conveyor 12 at least by an amount sufficient to
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accommodate the difference between their thickness and
their width.
An important feature of the invention is,
however, the provision of a return conveyor 24 which
moves at a speed greater than that of the mold blocks
16 and carriers 17 on tunnel conveyor 12.
The speed of blocks 16 and carriers 17 on
tunnel conveyor 12 is dictated by the length of the
conveyor, the speed of extrusion, the thickness and
diameter and cooling conditions of the molded tube and
on other parameters. On tunnel conveyor 12 the mold
blocks 16 must lie with adjacent faces in contact to
form the tunnel. On the return conveyor 24, however,
these parameters do not apply and, therefore, a mold
block 16 and carrier 17 may be peeled of the
downstream end of the mold tunnel, speeded up and
returned to the upstream end of the mold tunnel, at
much greater speed than that of blocks on the tunnel
conveyor 12.
Thus, for example, the mold tunnel may
comprise ten mold blocks 16 on respective carriers 17,
the length of the mold tunnel is 100 inches, each mold
block having a thickness of 10 inches and width of say
50 inches. In this case, the distance of the removal,
return and approach conveyors 22, 24, 26 is at least
50 + 100 + 50 inches. In practice, of course~ it will
be more than this so that there is room for operating
machinery between the tunnel and return conveyors 12,
24. In fact, it is emphasized that the numbers chosen
for exemplification are only numbers chosen for simple
calculation rather than examples of practical speeds
and dimensions which may be used.
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In the example it will be seen that the
total length of the return runs is 200 inches and the
length of the tunnel run is 100 inches. If the speed
of a block on tunnel conveyor 12, is 1 inch per minute
it will take 10 minutes for a block 16 to move
sufficiently far along tunnel conveyor 12 to allow the
addition of another block 16 at that end.
If the average speed of block on the
removal, return and approach conveyors is 22, 24, 26
is 10 inches per minute, it will take only 20 minutes
for a block 16 to peel off the downstream end of the
tunnel, and travel to the upstream end for readdition
to the tunnel.
It may seem that unlike the systems of the
prior art in which there were as many blocks on a
return run as on a tunnel run, the present invention
may offer the advantage of utilizing a lesser number
of blocks on the removal, return and approach runs as
on the tunnel run. This may result in reduction in
manufacturing costs, material costs and running costs
of equipment. Any such savings are of considerable
importance in the provision, supply, and running of
the heavy machinery necessary ~or the molding of large
diameter pipe.
When the average speed of the removal,
return and approach conveyors 22, 24, 26 are greater
that that of the blocks 16 on the tunnel conveyor 12,
it is thought that return conveyor 24 may conveniently
run faster than the removal and approach conveyors 22,
26.
The position of hinge 28 and the comparative
size of the mold block parts which are hinged together
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about the hinge are a matter of choice. However, it
is found that the apparatus may of~er advantages for
the molding of large diameter tube. For example, tube
diameter greater than 12" is moldable using the method
and apparatus according to the invention.
As shown in Figures 1, 3, 4, 5, 9 and 10 the
hinge of each mold block 16 is located at the top of a
mold block 16 and connects mold block parts 13, 15
each of which comprises roughly half the mold block 16
although a~y convenient propor-tion may be chosen.
When hinge 28 is at the top of the mold
block, it is preferable to shape the fixed part 13
~conveniently referred to as halves~, fixed half 13,
so that it includes the whole of the base of the mold
block which connects with carrier 17 in any
conventional manner. Thus the guide blocks may
suitably have the shape illustrated in Figures 3, 4
and 5. These guide blocks have faces 42, 43 adjoining
the hinge 28 which are flush with each other when the
guide block is closed to lie radially of the mold
tunnel. These blocks also have faces 44, 45 which are
flush with each other when the guide block is closed
and spaced apart from one another when the guide block
is open. These faces, when the guide block is closed,
lie in a plane which is oblique to the radius of the
tunnel.
~ guide block as shaped from two assymetric
sectors as shown in Figures 3, 4 and 5 is advantageous
in some respects in that it is easy to remove from the
formed tube 200 As shown, with the hinge at the top
most point of the block and the opening of the tunnel
at the lower most point of the tunnel, the block is
easily withdrawable from the tube in a direction
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orthogonal to it, for e~ample, on the removal conveyor
22. When the block has this shape, there is no
interference or dragging on the tube 20 when the
opened block ]6 is pulled away from it.
Another desirable shape of mold block is
shown in Figures 6 and 7. In this case, the two
halves 13, 14 of the block 16 are symmetric and thus
have advantages in manufacture. The hinge 28 is
offset from the top of the mold block and fixed half
13 is attached carrier 17. In this case, both pairs
of faces ~2, 43 and 44, 45 are radial to the tunnsl
when the mold block is closed. However, because the
hinge 28 is offset from the uppermost point of the
mold block, the lower opening point of th~ mold block
is not coincident with the lowermost point of the
tunnel. Thus when an attempt is made to pull the mold
block away from formed tube 20, it will tend to drag
the tube 20 with it if is pulled in a strictly
horizontal direction. In this case, it is desirable
to adjust the level of removal conveyor 22 to be
slightly lower than that of tunnel conveyor 21. The
dif~ere~ce in height between tunnel conveyor 12 and
removal conveyor 22 may be the same as the difference
in height between the lower opening point 46 of the
mold block and the lowest point of the tunnel 47. The
conveyors 12, 22, 24 and 26 may all be in the same
generally horizontal plane. Any slight reduction in
height of conveyor 22 is being very slight and may be
regarded as being within the same general horizontal
plane as the upper runs of the other conveyors.
From conveyor 22 the mold blocks 16 and
carriers 17 are transferred to return conveyor 2~
which may, as shown, run parallel and opposite to the
direction of tunnel conveyor 12. On return conveyor
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24, the mold blocks 16 and carriers 17 are again
travelling in the direction of the tunnel axis and
will probably, due to the speed, be close together in
tunnel formation and, again linked through T-bars 100
and T-grooves 102. There is, however, no theoretical
need to ensure that they fit tightly together with
their upstream and downstream faces in tight flush
fit. Nor is there a need to provide for accurate
alignment of the tunnel. Therefore, for conveyor 24,
there is no need to provide a track similar to track
3~.
At the end of conveyor 24 the mold blocks
change direction again onto approach conveyor 26 in a
similar manner to the changes of direction before
described. When on approach conveyor 26, at least
when approachi~g extrusion nozzle 18, it is important
that the mold blocks be in open position, it is
possible to start closing the mold blocks before they
r~ach extrusion nozzle 18, provided there is
sufficient clearance between the hinged half 14 and `
the extrusion nozzle as the mold moves into position
for the start of another mold tunne:L run.
As the open mold block 16 approaches the
beginning of the mold tunnel conveyor 12 and the
e~trusion nozzle 18, it may be closed by any
convenient means.
One means of openin~ and closing the mold
blocks 16 is shown in Figure 1. A cam track 50 ma~
be provided following the general layout of conveyors
12, 22, 24, 26. Cam track may be of C-section to
accept and retain the heads of 60 mushroom lugs 52
(exteriors) outNardly from hinged half 14 of each mold
block. Along the tunnel conveyor 12, a continuous
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cam track 50 opens inwardly and is located at a height
lateral of the conveyor 12, as to maintain the mold
blocks closed. As the downstream end of conveyor 12
approaches, cam track 50 rises to hingedly raise each
mold hal~ 14 and open the mold block 16. The path of
cam track 50 follows the track of the leads 60 of the
mushroom lugs 52 and, as the mold blocks 16 changes -
direction onto the removal conveyor, twists so that it
opens downwardly. The cam track 50 may rise to
hingedly raise the mold half 18 through 180 but this
is not necessary. It may be easier to only open the
mold block 16 sufficiently for removal of tube 20.
The cam track 50 may be maintained at this height over
the removal conveyor 22, the return conveyor 24 and
the approach conveyor 26. At the downstream ena of
the approach conveyor 26, the cam track descends to
close the mold block 16 and twists to open again
towards the tunnel conveyor 12.
A preferred manner of opening and closing
the mold blocks 16 is illustrated in Figures 8, 9, and
10, which illustrate a mold block 16 and a carrier 17
having mold opening mechanism carried by the carrier.
This mold opening mechanism comprises screw threaded
vertical spindle 34 carried in an upstanding framework
side 36 of carrier 17. At its lower end spindle 34
carries sprocket wheel 38 geared to actuating sprocket
wheel 40.
Actuating sprocket wheel 40 may be powered
by any convenient means such as an electric motor or
other motor. Alternatively, at least on the tunnel
run, a rack 46 may be provided so that motion of the
carriers past the rack 46 will engage wheel 40 or 38
to turn spindle 34.
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Turning of spindle 34 in the direction shown
by arrow B in Figure 9 will lower block 48 engaged on
the spindle 34. Block 48 has an axle 62 projecting to
either side of it carrying one end of an articulated
arm 64, comprising a member 65 hinged to hinged mold
block half 14, a member 66 hinged to fixed mold block - .
half 13, a rigid link 67 pivotally connected at its ~; ,
respective ends to members 65 and 66, and a member 68
pivotally connected at one end to member 66 and link
678 and, at the other end to block 48.
As block 48 descends spindle 34 the action
of articulated arm 64 is to open mold block as shown
in Figure 10.
The outer surface of mold blocks 16 may have
cooling ribs 70.
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2245b/2-20
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