Note: Descriptions are shown in the official language in which they were submitted.
EXTRUDER BARREL CONSTRUCTION
This invention is concerned wi-th an extruder barrel
construction for an extruder, especially an extruder suitable
for homogenizing and extruding plastics or rubber materials.
In the field of extruders i-t is known -to enhance
the homogeniza-tion of materials by providing in the extrusion
chamber a screw having interrupted helical Elights and
obstacles projecting from the sides oE -the chamber arranged
-to cooperate with the flights of the screw, namely so-called
"pin-barrel" extruders.
U.K. Patent No. 1,440,682 granted to Uniroyal AG
on June 23, 1976, for example, discloses one such single
screw extruder for mixing and homogenizing viscous materials
wherein the extrusion zone of -the extruder comprises a screw
having two discontinuous flights enclosed in an extruder
barrel containing a series of obstacles projecting from the
sides thereof towards the root of the screw. The interrup-
tion of the flights thus provides channels at the root of the
screw into which the series of obstacles project. Each
series of obstacles comprises eight obstacles distributed
around the circumference of the barrel.
As a result of extensive wear of the internal
surface of the extruder barrel caused by abrasion and wear
as the fligh-ts convey the material to be homogenized through
the extrusion chamber, it is common practice to provide a
very hard and wear-resistan-t lining. Such linings may be of
bi-me-tallic material and are very brit-tle. They are also
very expensive -to produce. For those ex-truders heretofore
known comprising obstacles projecting into the extrusion
chamber, it is necessary to drill holes through bo-th the
sides of the barrel and the hard lining ma-terial so tha-t the
obstacles may be inserted into the holes thus provided and
secured therein by fastening means. Drilling of holes
through the lining is difficult if damage to the lining is
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to be avoided; damage to the lining can lead to unsatisfac-
tory performance and, if severe, may necessita-te provision
of a new lining.
As a result of breakage of one or more of the
obstacles, thus requiring replacement -thereof~ or wear or
damage -to the lining ma-terial, it is commonly necessary to
replace the lining material and/or obstacles. Such a process
is time consuming ancl laborious, involving removing -the
lining from the barrel (also, if any of the obstacles have
been bent, removing and replacing these may be a problem),
providing a new lining in replacement and furthermore drill-
ing holes in the lining to accommodate the obstacles. In a
large bore extruder this may prove to be very expensive both
in capital outlay and lost production time.
I-t is an object of this invention to provide an
improved extruder which may be assembled and dismantled
easily for replacement of inner parts.
The invention provides in one of its broad aspects
an extruder which is characterized by a plurality of barrel
modules arranged in alignment. A-t least two adjacent barrel
modules have a plate secured between each pair of adjacent
barrel modules. Each plate and each barrel module is inter-
changeable. Each plate is formed of two or more arcuate
parts. Each plate has an opening passing therethrough and
comprises projections extending into the opening. The open-
ing of -the plate and in-ternal surfaces of the barrel modules
form a substantially continuous passageway which provides an
ex-trusion chamber of a barrel of -the ex-truder and a screw in
the extrusion chamber having one or more helical f]ights
projecting from a roo-t portion of the screw. The flights
are discon-tinuous and arranged to leave annular spaces
be-tween adjacen-t fligh-t sections into which -the projec-tions
extend towards the roo-t of -the screw. The barrel modules
are provided with external flanges extending around end
portions thereof. The flanges contain a plurality of bore
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holes which correspond to bore holes passing through a
respective part of a plate around the external circumference
thereof, so that the plate parts are secured between
two adjacent barrel modules by fastening means inserted in
aligned bore holes of the plate parts and external flanges.
The plate parts are removable in a radial direction when the
fastening means are removed from the plate parts.
According to a still further broad aspect of -the
present invention there is provided a method of constructing
an extruder barrel charac-terized by a plurali-ty of barrel
modules and at least one plate formed of two or more arcuate
parts having an opening passing therethrough and comprising
projections extending into the opening. The plate or plates
comprise bore holes located around the circumference thereof
arranged to correspond with the plurality of bore holes
provided in external flanges which extend around end portions
of the barrel modules such that the two adjacent barrel
modules and the interposed plate parts may be secured
together by the insertion of fastening means into aligned
bore holes in adjacent flanges and pla-te parts. The plate
parts are removable in a radial direction when the fastening
means are removed.
An extruder according to the invention may be of
any convenient size in respect of the diameter of -the
ex-trusion chamber
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1 and the length thereof, however it is envisaged that the
construction according to the invention will particularly be used in
large extruders where there is a high cost in terms of tirne and
materials in replacing the lining rnaterial. The invention is
particularly suitable for extruders having an extrusion chamber
greater than twenty centimetres in diameter.
For ease of construction of an extruder barrel, in an
extruder according to the invention, which is preferably assembled
around the screw, the plate interposed between two barrel modules
preferably comprises two or more parts which are releasably secured
together. We prefer to use a plate comprising two parts, more
preferably two semi-circular parts. The -two or more parts of the
plate are preferably interchangeable in order that they may be used
in substitution for one another. The projections of the plate which
extend into the opening thereof may be of any desired shape for
example of square or circular cross-section. Also it may prove
advantageous to provide projections of different shapes in a
particular section of, or throughout7 the barrel.
The plate rnay comprise any convenient number of
projections. For a plate comprising two semi-circular parts we
prefer to have an even number oF projections. For maximum effect
we prefer to employ a plate having from ~ to 12 projections. The
projections may be provided, if desired, with pressure transducers
and therrnocouples to measure the conditions of pressure and
temperature existing within the extruder barrel. As the plates are
individual parts they may be produced from a variety of materials,
chosen according to the desired use.
The extruder barrel is conveniently constructed by
interposing a plate between at least two adjacent barrel modules of
the plurality of aligned barrel modules and securing it therebetween
1 in sealing relationship therewith, so that no material may leak From
the extruder barrel at the junctions of plate and barrel modules or,
where a multi-part plate is used, between joints in the plate. The
barrel modules are provided with external flanges extending around
end portions thereof, the flanges containing a plurality of bore
holes which correspond to bore holes passing through the plate
around the external circumference thereof. The plate is secured
between two acdjacent barrel modules in sealing relationship by
fastening means inserted in aligned bore holes of the plate and
external flanges.
In a preferred form, an extruder according to the
invention comprises a plurality of plates, each plate being secured
between two adjacent barrel modules. In order to attain
satisfactory homogenisation oF the material contained therein, we
prefer to construct the extruder barrel so that a plate is
interposed between each two adjacent barrel modules in a
homogenisation zone of the barrel. Conveniently the plates are
interchangeable so that they may be used in substitution for one
another as desired.
The barrel modules of an extruder according to the
invention preferably each comprise an outer shell having external
flanges extending around end portions thereof and a lining material
slideably received within said outer shell. The lining material is
composed of a hard, wear resistant material and suitably comprises a
self-supporting material which may be inserted into or removed from
the outer shell of the barrel module as desired. Conveniently the
outer shell comprises means for retaining the lining material
therein, for example in a preferred embodiment~ the outer shell
comprises an internal flange which supports the self-supporting
cylinder of lining material~ This arrangement provides a cavity,
1 extending around the lining material between the lining material and
the outer shell for heat ex~change liquid which is employed to supply
heat to or remove heat from the extruder barrel as desired, thereby
providing a so-called wet liner. In such a module construction the
flow of heat exchange liquid through each module can be controlled,
if desired, independently of the other modules, thereby giving
improved control of temperature and providing individual temperature
zones. Alternatively, a wet liner may be sealed around the extrwder
barrel by any of the normal methods. The barrel modules may be oF
any convenient construction. Preferably, however, each of the
barrel modules are identical so that they are interchangeab1e and
each may be used in substitution for any one of the other modules,
as desired. ~here the barrel modules are to be interchangeable, the
outer shells and lining material may conveniently be manufactured
using numerically-controlled machine tools which facilitate the
manufacture of barrel modules that are identical.
Interchangeability of the barrel modules, the plates and
the parts thereof is of significant advantage. As the material is
conveyed by the helical flights of the screw through the extrusion
chamber, some of the parts of the chamber sustain more wear than
other parts thereof, for example, the outlet end of the extrusion
chamber receives considerably more wear than a central part of said
chamber.
In some cases it may be convenient to replace a worn or damagec1
barrel module, a plate or parts thereo-f, with a new replacement part
which has been removed from a part of the extrusion chamber that has
sustained less wear. Interchanging of worn with less worn mot1ules
ensures that optinlum wear is achieved from the modules and provitles
a significant saving in cost, as compared with an integral barrel
construction in which, should part of the lining become too worn,
1 relining of the whnle barrel would be necessary at a considerable
capital outlay and lost production time. Where the modules are
identical production loss can be minimised by keeping one or more
spare modules. Also, the provision of a part having a number of
projections, which may be inserted into the extruder barrel of an
extruder according to the invention in sealing relationship
therewith, without the need to drill holes in the lining material
for the insertion of projections, avoids the possibility of having
to replace the lining material resulting from damage thereto arising
from drilliny holes in said lining material. This construction also
makes it possible to substitute plates with different projections to
modify the extruder perFormance.
The invention provides in another of its aspects a method
of constructing an extruder barrel comprising a plurality of barrel
modules and at least one plate having an opening passing
therethrough and comprising projections extending into said opening,
wherein the 'or each) plate is interposed and secured between
adjacent barrel modules so that the opening of the (or each) plate
and internal surFaces of the barrel modules form a substantially
COntinuQuS passageway providing an extrusion chamber of the barrel.
In a preferred method according to the invention the plate or plates
comprise bore holes located around the circumference thereof
arranged to correspond with the plurality of bore holes provided in
external flanges which extend around end portions of the barrel
modules, so that tWQ adjacent barrel modules and the interposed
plate may be secured together by the insertion of fastening means
into aligned bore holes in adjacent flanges and plate.
The invention further provides in another of its aspects a
barrel module for use in an extruder according to the invention
wherein the barrel module comprises an outer shell having external
1 flanges extending around end portions thereof and a lining material
slideably received within said outer shell9 the arrangement being
such as to provide a cavity for heat exchange liquid which extends
around the lining material between said lining material and the
outer shell.
lhe invention further provides in another oF its aspects a
plate for use in an extruder according to the invention wherein the
plate has an opening passing therethrough and comprises projections
extending into said opening and further comprises bore holes passiny
through the place around the circumference thereof.
Whereas reference has only been made herein to a single
screw extruder it is intended that the construction of the invention
may also have application in twin or ~ultiple screw extruders.
There now follows a detailed description to be read with
reference to the accompanying drawings~ of an extruder suitable for
use in the homogenisation and extrusion in shaped form of plastics
and rubber materials. It will be realised that this extruder has
been selected for description to illustrate the invention by way of
example.
In the drawings:-
Fiyure 1 is a side view partly in section of part of an extruder
according to the invention;
Figure 2 is a section along the line II-II of Figure 1;
Figure 3 is a view in section along the line Z-Z of
Figure 2, and
Figures 4 5 and 6 are views in section along the line Z-Z showing
alternative projections which might be used in an extruder according
to the invention.
The extruder 2 shown in Figure 1 comprises an extruder
barrel and an extruder screw 8. The extruder barrel comprises a
1 plurality of barrel modules 4 ancl plates 6 arranged in alignment and
secured ~oyether to form a substarrt-ially continuous passayeway which
provides an extrusion chamber 3 of the barrel.
The barrel modules 4 are of circular section and are
identical so that they may easily be interchanged and used in
substitution for one another. Each module comprises an outer shell
10 and a lining material 16 adapted to be received within the outer
shell 10. The outer shell is provided with two external flanges 12
having a plurality of bore holes, which flanges extend around the
circumference of the outer shell one at each end portion thereof.
The outer shell 10 is aîso provided with internal flanges 14, one at
each end portion thereof, which extend around the internal
circumference of the outer shell 10. The lining material 16
comprising a self-supportiny cylinder of 533mm internal diameter is
composed of a suitable wear resistant material, viz. Xalloy, and is
slideably received within the outer shell 10. It is retained
therein by the internal flanges 14 of the outer shell. This
arrangement thus provides a cavity 18 between the lining material 16
and outer shell 10 having inlet and outlet openings 20, 22 for heat
exchange liquid which can be arranged to heat or cool the extruder
barrel 3, as required. The heat exchange liquid is sealed within the
cavity 18 by '0' rings 24 located in recesses in the internal
flanges 14.
The plates 6 (shown more clearly in Figure 2) comprise two
substantially semi-circular portions 36, 38 and are 5cm in
thickness. The two portions 36, 38 are releasably secured together
by two screws 40. Each plate 6 has a circular opening 26 of 533mm
diameter passing therethrough. Bore holes, corresponding to bore
holes in the external flanges 12 of the barrel modules 4, passing
through the plate parallel to the direction of the opening 26~ are
1 provided around the external circumference of the plate 5. The
plate is also provided with five pairs of diametrically opposed
rectangular projections 30 tapering -from 5cm square at a base
portion 29 to 3.8cm square at a tip portion 31, which extend into
the opening 26. When the extruder 2 is assembled the projections 30
extend towards the root 9 of the screw 8 so that only a small gap
exists between the tip portions 31 of the projections and tne root 9
of the screw 8.
On assembly of the extruder barrel 3, the barrel modules 4
are aliyned with a plate 6 interposed between each pair of barrel
modules 4 in sealing relationship, so that no material contained
within the barrel may leak out at the junctions between the plate,
the parts of the plate and the barrel modules. The bore holes of
the external flanges 12 and the bore holes of the plate 6 are
aligned so that two adjacent barrel modules 4 and the interposed
plate may be secured together by the insertion of fastening means 28
provided by nuts and bolts into said bore holes in adjacent flanges
and plate.
The screw 8 of the extruder is provided with two
discontinuous helical flights 32 projecting from the root 9 of the
screw 8, their arrangement leaving an annular space 42 between
adjacent Flight sections into which the projections 30 extend
towards the root of the screw.
The extruder 2 is supporte~ by a support frame (not shown)
which engages grooves 34 passing through external flanges 12 of the
barrel modules 4 and the plates 6.
The screw 8 is mounted for rotation in bearings carried by
the frame (not shown) of the extruder and driven through gear means
(not shown) by a suitable motor (not shown) in known manner.
1 The extruder barrel is assembled around the screw 8 as
hereinafter described. A first barrel module 4 encompassing the
screw 8 is passed along the length of the screw, the grooves 34 in
the external flanges 12 in engagement with the support frame (not
shown), until the flanges of a leading end portion of the module
abut a sealing face of the frame of the extruder to which the
external flange 12 of the leading end portion is secured by bolts.
Bolts of the fastening means 28 are then inserted into the bore
holes of the flange 12. The two portions 38, 36 comprising the
plate 6 introduced from upper and lower directions respectively, are
placed adjacent the barrel module 4, with the projections 30
extending towards the root 9 of the screw 8 in the annular space 42,
and the bore holes of the plate 6 receiving the bolts of the
fastening means carried in bore holes of the external ~lange 12.
The portions 36, 38 are secured together by means oF screws 40. A
second barrel module 4 encompassing the screw 8 is then passed along
the length of said screw until it abuts the plate Ç, the bolts
projecting from the plate 6 recei~ed in the bore holes in the flange
12 of the seconcl module 4; thus the bore holes of both external
flanges 12 of the barrel modules are aligned with those of the
plate. The flanges and plate are then secured together by
application of a nut to each of the bolts. This process is repeated
until the complete extruder barrel is formed, a plate 6 following
each barrel module 4 in consecutive arrangement.
When it is desired to replace a plate 6 as a result of
wear or breakage, etc., the fastening means 28 is unscrewed and
withdrawn, and the plate removed from the extruder barrel 3 by
unfastening the screw 40 securing portions 38 ancl 36 together,
followed by removal of said portions in upward and downward
directions respectively.
1 A new plate may be substituted therein by reversing the
process hereinabove described but without the necessity for
completely dismantling the barrel, the two parts of the plate being
inserted readily from above and below between two adjacent modules
space~ apart sufficiently.
