|Title of Invention
|A multiple-shaft extruder comprises a core (4) with outward leading channels that can be flown through by a cooling liquid. At least two housing segments (16 to 19) are each provided with a cooling circuit with interconnected cooling bore holes (28), which can be flown through by a cooling liquid, are distributed in the peripheral direction and in an axially parallel manner, and which are located on the section of the housing segments (16 to 19) that faces the process chamber (2).
 This invention relates to an extruder according to the preamble of claim 1.
 Such extruders are known (EP 0788867 Bl; EP 0995566 Bl). The housing
is divided into segments, The segments can be provided e.g. with material feed
openings, gas outlet openings, heating means, cooling elements and the like to permit
the extruder to be adapted flexibly to the material processing to be carried out in the
 Compared to a double-shaft extruder, such multi-shaft extruders with
annularly disposed shafts have the advantage of having twice as many wedges on
which material is processed particularly effectively by being transferred from the
processing elements of one screw to the next. For example, an extruder with twelve
shafts has 24 wedges, i.e. each shaft has two wedges associated therewith, while a
double-shaft extruder has only two wedges, i.e. each shaft has only one wedge
associated therewith. Being the effective processing zone, each wedge has heat
produced thereon by additional stretching and compressing of the product. The high
number of wedges thus leads in multi-shaft extruders to an increased accumulation of
heat, which increases the temperature of the material to such an extent that the material
can be overstressed. It is therefore known from WO 02/30652 A1 to form the housing
in one piece and provide circumferentially distributed, axially parallel bores as cooling
channels not only in the housing but also in the core.
 The problem of the invention is to ensure an optimal temperature for
processing in the process chamber of a multi-shaft extruder having a housing
constructed of segments, and a material temperature as low as possible upon discharge
from the process chamber.
 This is achieved according to the invention by the extruder characterized in
claim 1. The subclaims render advantageous embodiments of the inventive extruder.
 The inventive extruder has a core provided with cooling channels through
which cooling liquid flows to ensure a heat exchange in the process chamber from the
inside and cool it. At least one, but preferably two or more, segments of the housing
are provided with circumferentially distributed, axially parallel cooling bores which
are interconnected, each segment being provided with a connection for a cooling liquid
feed and a connection for a cooling liquid drain through which cooling liquid is
supplied to the cooling bores and discharged therefrom. The cooling bores are
disposed on the portion of the segment facing the process chamber and thus as near as
possible to the process chamber.
 The housing segment provided with the cooling bores has at the same time a
heating means on the outside circumference. Each housing segment provided both
with cooling bores and with a heating means preferably has a control device which
controls both the heating means and the flow of cooling liquid through the cooling
bores to permit adjustment of an optimal processing temperature and a material
temperature as low as possible. The cooling liquid flow through the cooling bores can
be controlled with a valve in the cooling liquid feed or drain. The temperature control
device has a temperature sensor which is provided in the housing segment to
determine the temperature in the process chamber. The heating means is used to heat
the housing segment in question when the extruder is started to adjust the predefined
operating temperature in the process chamber. If the operating temperature is exceeded
during extrusion, the temperature control device switches the heating means off and
cooling liquid is supplied to the cooling bores in the housing segment, controlled by
the temperature control device, to maintain the predefined operating temperature
pattern and control the heat removal differently from zone to zone. The housing
generally consists of at least three housing segments, whereby preferably all, but in
any case the majority, of the housing segments are adapted to be coolable and heatable
in this way.
 The core assumes the temperature near the product from the process section
and is therefore - unless an internal axial heat exchange takes place - near room
temperature at the upstream conveying end and near the higher product outlet
temperature at the downstream conveying end. By intensification of the axial heat
transport with a corresponding choice of materials and their design or e.g. with the
help of a viscous heat carrier, the product temperature can be lowered on the outlet
side, on the one hand, and increased to the point of equalization in the direction of
product feed, on the other hand. If a heat surplus is still present, it must be dissipated
to the outside by the coolant, which can alternatively be effected at each end of the
 The cooling channels of the core are preferably formed by an axial bore and
an outside channel disposed spirally around the axial bore and extending near the
process chamber. Both the axial bore and the spiral outside channel extend over the
total, or at least most of, the process chamber and preferably serve to adjust a low
material outlet temperature.
 The cooling liquid flows via a cooling liquid feed at the upstream conveying
end of the core, which is adjacent the drive for the shafts, into the axial bore in the core
and then in the conveying direction of the extruder to the downstream, conveying end
portion of the core, where the product outlet openings are located. The downstream
conveying end of the axial bore is connected to the downstream conveying end of the
spiral outside channel, causing cooling liquid in the spiral outside channel to flow back
to the cooling liquid drain at the upstream conveying end of the extruder in
countercurrent to the conveying direction of the shafts.
 The process chamber of the extruder is preferably sealed with end plates on
the downstream and upstream conveying ends. While the extrusion die is attached to
the downstream conveying end plate, the upstream conveying end plate is preferably
penetrated by the core, the cooling liquid feed and cooling liquid drain to and from the
cooling channels in the core being provided on the end portion of the core protruding
from the upstream conveying end plate.
 The core could be executed in one piece for non-wearing products, but as a
rule it consists of a hollow drilled mandrel containing a well-fitting distributor on
whose surface the desired cooling channel pattern is incorporated preferably in a spiral
shape. The mandrel bears segments positioned in rotationally fast fashion whose outer
form again partly encloses the axially parallel screws with little play.
 For connecting the cooling liquid feed and drain, an annular segment is
disposed on the upstream conveying end of the core, which protrudes from the
upstream conveying end plate, said segment being provided with radial bores for
connection to the axial bore and the outside channel. The annular segment with the
radial bores can be formed as a plate through which the shafts for the drive extend.
 The outside channel is preferably formed by a spiral groove on the outside
circumference of the distributor, which is sealed from the process chamber by the
mandrel. The radial bores for connecting the cooling liquid feed and drain are guided
through the mandrel.
 The mandrel preferably has sleeve-shaped segments disposed thereon in
rotationally fast fashion e.g. by splining with the mandrel so as to form the axially
parallel, circular segment shaped recesses. Since the sleeve-shaped segments are
usually exposed to different wear on the inner side of the process chamber, they can
thus be selectively replaced.
 The housing segments can partly have radially extending openings for
connecting the process chamber to the outer surroundings in order to supply
substances to the process chamber or remove them therefrom, for example gases. The
openings preferably extend horizontally, thus being disposed on the side of the
housing, or vertically, i.e. upward or downward. The openings can be provided with
fixed fittings, for example a funnel, or movable fittings, for example a screw conveyor.
They can also be sealed when they are not needed.
 The housing segments can be interconnected by flanges. However, they are
preferably held together tightly by tie-rods with prestressing. At least three tie-rods
offset at an angle of 120° are preferably provided to obtain high contact pressure on
the entire circumference between the segments. Because of the vertically and
horizontally extending openings in the housing segment, however, four tie-rods are
preferably used which are offset by 45° from the horizontal or vertical.
 The tie-rods extend through axially parallel bores in the housing segments
and thus at the same time serve to mutually position the housing segments radially.
The tie-rods can also have a smaller diameter than the bores in the housing segments
through which they are guided. To ensure the mutual radial positioning of the housing
segments, a plurality of sleeve-shaped filler pieces are then slipped successively on the
tie-rods. The sleeve-shaped filler pieces have the advantage that the housing segments
can be removed singly upon dismantling of the housing, so that the housing does not
fall apart as a whole when the pull rods are drawn out.
 The pull rods preferably attack at one end the downstream conveying
housing segment and at the other end an annular plate provided on the downstream
conveying side of the material feed opening. Said plate can be used to fasten the
extruder to a machine frame. Thus the torque and tractive forces occurring in the
housing during processing of the material are transmitted via this plate into the
machine frame so as to bypass the housing segment with the material feed opening.
Thus the housing segment with the material feed opening is not attacked by any
appreciable axial or torsional forces. It can thus consist of two axially spaced plates
between which a thin wall, for example made of sheet metal, is detachably fastened.
This permits fast thorough cleaning of the screw elements on the shafts in the feed
area, since the material which is still powdery in this area is frequently deposited
firmly on the screws.
 The segment with the material feed opening is preferably followed on the
downstream conveying side by a segment with a funnel-shaped inside wall tapering in
the downstream conveying direction. Said funnel-shaped feed segment causes a ring of
material to form around the shaft, which leads to uniform material distribution in the
process chamber. The funnel-shaped feed segment can extend into the plate which is
attacked by the pull rods at their ends.
 While the segmented housing and the core are fixed relative to each other
radially and in the circumferential direction, the housing is formed to be axially
movable relative to the core in order to compensate temperature differences between
housing and core. For this purpose the housing can be mounted so as to be axially
displaceable on the core on the upstream conveying side of the material feed opening.
 The housing segments between the plate which is supported on the machine
frame, and the downstream conveying end plate usually consist oflong and short
segments. The long segments are provided with the heating means and with the
cooling bores. The short segments serve primarily to feed and remove substances and
are therefore provided with openings for connecting the process chamber to the outer
 As mentioned at the outset, the higher energy conversion in the wedge is
fundamentally advantageous for uniform and intensive processing of the product.
Particularly high pressure is often necessary for pressing the fully processed substance
through a perforated plate, screen or the like at the product discharge. Because of the
subsequently often relatively long residence time during shaping, the product
temperature must be as low as possible. Since the wedge makes an essential
contribution only to homogenization but not to pressure buildup, it is not absolutely
necessary for the discharge area according to the invention. Since only the suitable
screws are guided as single-shaft or twin screws up to the end of the housing and the
others end before the discharge area, this finding is easy to utilize. A twelve-shaft
extruder has twelve engagement zones and thus twenty-four wedges. If every third
screw shaft, i.e. altogether four screws, end before the discharge area, four twin screws
with four engagement zones or eight wedges result. If every second screw, i.e. six, end
before the discharge area, six single-shaft screws remain up to the end of the housing,
and the engagement zones or wedges are completely eliminated. This does not result in
a reduction of delivery volume since the strand cross sections and likewise the number
of strands remain unchanged. For example, a twelve-shaft ring extruder equipped with
double-threaded screws divides the product into twelve strands of material, the same
as a twin screw divides it into three strands of material, and a single-shaft extruder into
two strands of material. With four twin screws and six single-shaft extruders there are
always twelve strands of material which, while the product is in the process section,
are divided up as in the twelve-shaft extruder. Under the same operating conditions,
the lowest material outlet temperature is obtained substantially in the single-shaft
extruder, and the highest in the twelve-shaft extruder.
 Since the shafts ending before the discharge segment arc exposed to lower
pressure, more economical axial bearings can also be used for said shafts.
 Hereinafter an embodiment of the inventive extruder will be explained more
precisely by way of example with reference to the drawing, in which:
 Figure 1 shows a longitudinal section through the extruder;
 Figures 2 to 6 show cross sections along the lines II-II, III-III, IV-IV, V-V
 Figures 7 and 9 show cross sections through the housing segment in the
 Figure 8 shows a developed representation of the cooling channels of the
housing segment according to Figures 7 and 9;
 Figure 10 shows a partial view of another embodiment of the extruder in
 Figure 11 shows a cross section along the line XII-XII in Figure 10 as a twin
screw discharge; and
 Figure 12 shows a cross section corresponding to Figure 11 for a single-shaft
 According to Figure 1 and Figures 2 to 4, the extruder has in a housing 1 a
process chamber 2 which extends along a circle (Figures 2 to 4). A plurality of axially
parallel shafts 3 are disposed in the process chamber 2. The chamber 2 extends
between the housing 1 and an axial core 4.
 The process chamber 2 is sealed on both faces by end plates 5,6. The shafts
3 extend through the upstream conveying end plate 5, being driven codirectionally by
a drive section not shown in the drawing. The material outlet openings 7 are provided
in the downstream conveying end plate 6.
 A plurality of screw or similar processing elements 8 are disposed in
rotationally fast fashion on each shaft 3. According to Figures 2 to 4, the screw
elements 8 of adjacent shafts 3 mesh with little play, i.e. largely tightly.
 The housing 1 is provided on its inner side with axially parallel, concave,
circular segment shaped longitudinal depressions 12, while the segments 11 of the core
4 likewise have accordingly formed axially parallel, concave, circular segment shaped
longitudinal depressions 13. The longitudinal depressions 12, 13 which the screw
elements 8 engage with little play, i.e. largely tightly, serve to mount and guide the
shafts 3. Between two adjacent longitudinal depressions 12; 13 on the inner side of the
housing 1 and the outer side of the segments 11, wedges 14, 15 are formed on which
the material to be extruded is transferred from the processing elements 8 of one shaft 3
to the next shaft 3.
 The housing 1 is composed of a plurality of longer annular housing segments
16 to 19 and shorter annular housing segments 21, 22 disposed therebetween. The
upstream conveying housing segment 19 is followed by an annular plate 23 which is
mounted on a machine frame not shown.
 The plate 23 has protruding thereinto a feed segment 24 with an inside wall
tapering in a funnel shape on the downstream conveying side. This is followed on the
upstream conveying side by a filler housing segment 25 with a material feed opening
26 and the end plate 5 fastened thereto. The filler housing 25 has on the underside a
cleaning opening which can be opened in readily accessible fashion with a cover 57.
 The segments 16 to 19 are each provided on their outside circumference with
electric heating means 27. Further, each housing segment 16 to 19 has on its portion
facing the process chamber 2 circumferentially distributed, interconnected, axially
parallel cooling bores 28 through which a coolant flows. To control the electric heating
means 26 and the cooling circuit 28, each housing segment 16 to 19 has associated
therewith a temperature control device not shown.
 The core 4 is of coolable and preferably multisectional design. The hollow
drilled mandrel 9 bears the segments 11 which are positioned in rotationally fast
fashion via a keying. The mandrel 9 contains a well-fitting distributor 99 provided
with an axial bore 29 and a spiral outside channel 31. At the upstream conveying end
the distributor 99 is provided with a cooling liquid feed 32 to the axial bore 29 and a
cooling liquid drain 33 from the outside channel 31.
 The core 4 penetrates the upstream conveying end plate 5 so as to be axially
freely displaceable and has on the free end an annular segment 34 which leads with a
radial bore for the cooling liquid feed 32 to the axial bore 29, and the outside channel
31 to the cooling liquid drain 33.
 The shorter segments 21 and 22 and the long downstream conveying
segment 16 are provided with radial openings 38, 39, 40 extending vertically upward.
Further, the segment 21 has two lateral, horizontally extending radial openings 41, 42
according to Figure 4. The upwardly extending opening 40 in the segment 16 and the
lateral openings 41, 42 in the segment 21 are sealed by stoppers 43, 44, 45. The
opening 39 in the segment 22 is provided with a fitting 46 with a screw conveyor.
 The housing segments 16 to 19, 21, 22 on the downstream conveying side of
the plate 23 are held together tightly with prestressing by tie-rods 48. According to
Figure 4, four bores 49 are provided in the housing segments for receiving four tie-
rods 48. The pull rods 48 attack at one end the downstream conveying housing
segment 16 and at the other end the plate 23. For this purpose the downstream
conveying end of the rod has screwed thereto a nut 51 which is supported on the
housing segment 16. At the upstream conveying end the pull rods 48 have screwed
thereto a further nut 52 in a recess in the plate 23, which is penetrated by clamp bolts
53 which are supported in the recess 54 on the plate 23.
 Fastened to the end plate 6 with the outlet openings 7 is a plate 61 which
bears the extruder head not shown. Number 62 designates a suspension permitting the
extruder head to be removed. The nuts 37 provided in the end plate 6 fix the core 4
relative to the housing 1 axially, radially and circumferentially. Screw bolts 65 are
used to fasten the end plate 5, the filler housing 25 with the material feed opening 26
and the feed housing 24 with the funnel-shaped inside wall to the plate 23. Sleeve-
shaped filler pieces 63 are slipped on the pull rods 48 (Figure 5). The recesses 64 on
the faces of the wearing segments 11 make it easier to remove the latter from the
 The housings 16 to 19 have separate cooling and hearing circuits. Figures 7
and 9 show cross sections through one of said housings. The housing itself is shown
for flange execution but it can also be executed with a solid outer cross section with
tie-rods. A wear-resistant steel is characterized by great hardness and is therefore
required on the product-wetted inner side of the housing. This material can either be
produced by powder metallurgy and sinter-fused under pressure and temperature, or a
separate inside body has been produced which is shrunk and/or bonded into the
surrounding actual housing. The outer housing is a softer, tenacious and, according to
the invention here, not necessarily weldable steel in which the axially parallel cooling
bores 1 to 12 are incorporated. The bores C-F-I-L are provided for the dowel pins or
the tie-rods and the frontal tapholes B-D-G-K are used for drilling the internal
connections between two adjacent peripheral cooling bores 1-2, 5-6, 8-9 and 10-11.
This results in four internally linked cooling circuits 1-2-3, 4-5-6, 7-8-9, 10-11-12
which are to be linked via outer connections, e.g. via the bridges B-C and H-J. The
usual welding of the connections between the cooling bores 1 to 12 is only possible
with separately produced inside bodies, since when an inner wearing layer is applied it
would otherwise be partially destroyed and the whole housing rendered useless.
 In the embodiment according to Figures 1 to 6, the discharge of the extruder
is formed by the portion with the housing segment 16, whereby all twelve screws 3 (cf.
Figure 4) extend up to the end plate 6. In contrast, according to the embodiment of
Figures 10 and 11, a special discharge segment 85 is provided, whereby two adjacent
shafts 3 extend through corresponding bores in the discharge segment 85 up to the end
plate 6, while the two adjacent shafts 3, one of which can be seen in Figure 1, end at
the discharge segment 85 as does the core 4. That is, every third one of the twelve
shafts 3 according to Figure 4 extends only up to the discharge segment 85. Thus, the
twelve shafts 3 which the extruder has according to Figure 4 form four double shafts
86 in the discharge segment 85, as evident from Figure 11.
 The core 4 is connected axially to the discharge segment 85 and fixed
radially antirotationally with a screw 87. Figures 10 and 11 show the discharge
segment 85 in one piece, but it can also be multisectional. For example, the core can
also extend into or through the discharge segment 85.
 The discharge segment 85 is provided with a heating means 27 on the
outside circumference in the same way as the housing segments 16, 17, etc., and
further with cooling bores 28 which are formed in the same way as the above-
described cooling bores 28 in the housing segments 16 to 19.
 The embodiment according to Figure 12 differs from that according to
Figure 11 substantially in that the product discharge is not effected by four twin screws
86 but by six single screws 3, since every second single screw 3 ends before the
discharge segment 85. It is also possible to provide both twin screws and single screws
in the discharge segment 85.
1. An extruder having a plurality of axially parallel, codirectionally rotating shafts
disposed in a process chamber between a housing and a core along a circle at
equal central-angle distance and equipped with processing elements with which
adjacent shafts mesh with each other, whereby axially parallel, circular segment
shaped longitudinal depressions are provided for receiving the shafts on the inner
side of the housing and the outer side of the core, the housing is composed of
housing segments, at least one of which is provided with a heating means, the
housing segment at the upstream conveying end has a material feed opening and
the discharge is provided at the downstream conveying end, characterized in that
the core (4) has outwardly leading cooling channels for a cooling liquid to flow
through, at least one housing segment (16 to 19) provided with a heating means
(27) has a cooling circuit with axially parallel, circumferentially distributed,
interconnected cooling bores (28) for a cooling liquid to flow through on the
portion of the housing segment (16 to 19) facing the process chamber (2), and the
at least one housing segment (16 to 19) has associated therewith a temperature
control device for controlling the heating means (27) and the flow of cooling
liquid through the cooling bores (28).
2. The extruder according to claim 1, characterized in that the cooling channels in
the core (4) are formed by an axial bore (29) and an outside channel (31)
disposed spirally around the axial bore (29), and the coolant is supplied at the
downstream conveying end and flows toward the upstream conveying end.
3. The extruder according to either of the above claims, characterized in that the
process chamber (2) is sealed by end plates (5, 6) at the upstream and
downstream conveying ends.
4. The extruder according to claim 2 or 3, characterized in that the core (4)
penetrates the upstream conveying end plate (5), and the cooling liquid feed (32)
and the cooling liquid drain (33) are provided at the end of the core (5)
protruding from the upstream conveying end plate (5).
5. The extruder according to claim 4, characterized in that the cooling liquid feed
(32) and drain (33) are formed by radial bores in a segment (34) which is
disposed on the end of the core (4) protruding from the upstream conveying end
6. The extruder according to claim 2, characterized in that the outside channel (31)
is formed by a spiral groove on the outside circumference of the distributor (99)
and sealed by a mandrel (9).
7. The extruder according to claims 1 and 6, characterized in that sleeve-shaped
segments (11) are disposed in the end plate (5) so as to form the axially parallel,
circular segment shaped longitudinal depressions (13).
8. The extruder according to any of the above claims, characterized in that at least
one housing segment (16, 21, 22) has at least one horizontally and/or vertically
extending, radial opening (38 to 42) for connecting the process chamber (2) to
the outer surroundings.
9. The extruder according to claim 8, characterized in that the opening (38 to 42) is
provided with fixed or moving fittings (46) for supplying or removing
10. The extruder according to claim 1, characterized in that at least some of the
housing segments (16 to 19, 21, 22) are held together tightly by tie-rods (48) with
11. The extruder according to claim 10, characterized in that at least three, preferably
four, tie-rods (48) are provided.
12. The extruder according to claim 10 or 11, characterized in that the radial
positioning of the housing segments (16 to 19, 21,22) is effected by the tie-rods
13. The extruder according to any of claims 10 to 12, characterized in that sleeve-
shaped filler pieces (63) are provided on the tie-rods (48).
14. The extruder according to any of claims 10 to 13, characterized in that the tie-
rods (48) attack at one end the downstream conveying housing segment (16) and
at the other end a plate (23) provided on the downstream conveying side of the
segment (25) with the material feed opening (26).
15. The extruder according to any of the above claims, characterized in that the
segment (25) with the material feed opening (26) is followed on the downstream
conveying side by a segment (24) with a funnel-shaped inside wall tapering in
the downstream conveying direction.
16. The extruder according to any of the above claims, characterized in that the
housing (1) and the core (4) are formed so as to be mutually movable axially on
17. The extruder according to claim 1, characterized in that the discharge is formed
by a discharge segment (85), whereby pairs of adjacent shafts (3) extend as
double shafts (86) into the discharge segment (85), and the two shafts (3)
adjacent the double shafts (86) only up to the discharge segment (85).
18. The extruder according to claim 1, characterized in that the discharge is formed
by a discharge segment (85), whereby every second shaft (3) extends into the
discharge segment (85), and the other shafts (3) end at the discharge segment
19. The extruder according to claim 17 or 18, characterized in that the discharge
segment (85) is provided on the outside circumference with a heating means (27)
and/or cooling bores (28) which correspond to the cooling bores (28) of the
housing segments (16 to 19).
20. The extruder according to any of claims 17 to 19, characterized in that the
discharge segment (85) is fastened to the core (4).
21. The extruder according to any of the above claims, characterized in that the
housing segment (16 to 19) is formed on the inner side by a material produced by
powder metallurgy and/or has a separate inside body.
A multiple-shaft extruder comprises a core (4) with outward leading channels that can be flown through by a cooling
liquid. At least two housing segments (16 to 19) are each provided with a cooling circuit with interconnected cooling bore holes
(28), which can be flown through by a cooling liquid, are distributed in the peripheral direction and in an axially parallel manner,
and which are located on the section of the housing segments (16 to 19) that faces the process chamber (2).
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|BLACH VERWALTUNGS GMBH & CO. KG
|HOHER STEG 10, D-74348, LAUFFEN, GERMANY
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date