Device for pelletizing vegetable material

A pressing or pelletizing device for compacting vegetable materials, in particular grass blades, is disclosed for use with a harvester. In order to reduce the pressing forces required for the pelletizing process, the pressing channels are heated up to a temperature above 100 degrees C. It has been demonstrated that by heating the pressing channels, local overheating of the device, which could otherwise lead to malfunctions, can be avoided. The pelletizing device has two co-axial hollow cylinders in which the pressing channels are delimited by radial lands which alternatively engage the pressing channels of the other hollow cylinder. The hollow cylinders are heated by means of a liquid circuit guided through the lands and linked to a heat exchanger that utilizes lost heat from the internal combustion engine of the harvester.

CROSS REFERENCE TO RELATED APPLICATION 
The present application is a continuation of copending application 
PCT/EP93/00990 filed Apr. 23, 1993. 
FIELD OF THE INVENTION 
The present invention pertains to a device for pelletizing vegetable 
material, especially straw material, into free-flowing pressed objects for 
preparing animal feeds, fuels for generating energy, or for further 
industrial processing. 
BACKGROUND OF THE INVENTION 
U.S. Pat. No. 4,824,352, discloses a pellet mill for processing coarse and 
long fibers, especially straw, into animal feed. The material is fed by a 
screw conveyor into an expanding hopper, which is arranged in the intake 
wedge of two hollow rolls, which are driven in a mechanically controlled 
manner and engage each other in the manner of toothed gears. A plurality 
of holes tapering in the radial direction lead from the root of the tooth 
into the interior of the hollow rolls. The teeth are elongated in the 
axial direction and roll on each other. The straw material introduced into 
the wedge area of the hollow rolls is compacted by the teeth penetrating 
into the gashes and it is pressed through the radial holes into strands, 
which break off in the hollow space of the hollow rolls and are removed 
axially from the hollow spaces. 
Practical work with such pelletizing devices shows that trouble-free 
pressing of large amounts of straw material is problematic, because the 
straw material coils up around the teeth of the hollow bodies and 
accumulates in the root of the teeth by the radial holes, increasing 
resistance, so that the rotating bodies keep becoming blocked. Such 
devices are definitely unsuitable for preparing pressed objects of high 
density from straw material for use as a fuel material or for industrial 
purposes, because the frictional resistance of the meshing teeth as well 
as of the conical holes is too high, so that the energy needed to drive 
the hollow rolls increases excessively and cannot be ensured with the 
conventional means at all. In addition, the residues of straw material 
deposited on the hollow roll are heated up to pyrolysis temperatures due 
to the increased compression action, and the carbonized residues thus 
formed also lead to breakdown of the pelletizing device in a short time. 
SUMMARY AND OBJECTS OF THE INVENTION 
The primary object of the present invention is therefore to improve the 
prior-art pelletizing device such that trouble-free pressing of straw 
material in continuous operation will be possible, and high throughput of 
straw material can also be achieved at a low drive output. 
According to the invention, a device for pelletizing vegetable material is 
provided. The device includes hollow rolls mounted in parallel to one 
another which are forcibly driven in opposite directions in relation to 
one another and engage each other with teeth. Pressing channels are formed 
between the teeth which lead radially to the interior of the hollow rolls. 
Straw material is compacted through the radial pressing channels and is 
broken off in the material of the hollow rolls and is removed from the 
interior in an axial direction. The teeth are formed of heatable webs 
elongated in the radial and axial directions. The teeth are connected to 
two flange bodies which are arranged coaxially and at spaced locations 
from one another to define therebetween a pressing chamber, the hollow 
rolls being surrounded by a housing. 
Due to the teeth being designed as webs elongated in the radial and axial 
directions, between which radial shafts acting as pressing channels are 
located, material that is in the pressing process is prevented from 
accumulating and from leading to blockage. 
Due to the axial extension of the webs and consequently of the pressing 
channels located between them as well, the said pressing channels have a 
narrow shape elongated in the axial direction, which leads to relatively 
wide and thin strands containing the pressed material being able to be 
formed corresponding to this shape, as a result of which a high throughput 
of material per unit of time can be achieved. The radial top view of the 
pressing channels is normally rectangular. However, if the thickness of 
the webs is made variable, e.g., crowned, in the axial direction, pressing 
channels with bulged cross section will be formed. 
In conjunction with the heating of the teeth, the radial extension of the 
teeth according to the present invention offers the advantage that the 
pressed material located in the shafts can remain exposed to the action of 
heat and pressure for a certain amount of time, which leads to a certain 
hardening and dimensional stability. The density of the pressed objects 
can thus be increased to the desired extent, and the pressed object can be 
used as a free-flowing fuel material or as a starting product for further 
industrial processing. 
Even though heating of the feeding and pressing members of a pellet mill 
has been known from U.S. Pat. No. 3,192,881, the compaction process 
applied is based on the application of centrifugal force and is unable to 
accomplish the task of the present invention. In particular, it is 
impossible to prepare pressed objects of high density. 
Furthermore, surrounding hollow rolls of a pelletizing device, whose rolls 
mesh in the manner of teeth, with a housing has been known from 
FR-A-1,371,346, in which case bulk material is claimed to be processed for 
pharmaceutical purposes, fertilizers or ceramic or mineral products. Aside 
from the fact that these applications belong to a different class, 
compaction in this prior-art system is also based on teeth rolling on one 
another, at the root of which radially extending holes acting as 
compaction channels are arranged. Nevertheless, it is still unable to 
accomplish the task of the present invention. 
In contrast, the webs in the object of the present invention do not roll on 
one another, and also do not touch each other during their penetration 
into the shafts located between the webs of the other hollow body. The 
edges of the webs pass by each other at a short distance only, which leads 
to shearing off of the straw material fed in forcibly by a pressure worm. 
Since only the shafts passing through radially are located between the 
webs, and no tooth root with a hole located in it is consequently 
provided, accumulation of the straw material being pressed, which tends to 
undergo carbonization, cannot occur, either. 
The essential advantage of the device according to the present invention is 
its high performance and efficiency, because very large amounts of 
material can be pressed per unit of time at a relatively low energy 
consumption. 
The hollow rolls include webs detachably connected to flange bodies. The 
webs have axially parallel holes for connection to heating medium lines. 
The housing surrounds the hollow rolls and is preferably designed as a 
heatable housing particularly with holes for connection to heating medium 
lines. 
The arrangement of the pelletizing device on a harvester such as a self 
propelled harvester whereby vegetable material can be mowed, picked up, 
crushed, conveyed, pressed and stored and wherein the device housing can 
be heated by waste heat of an internal combustion engine of the harvester; 
offers the considerable advantage that the pelletization of straw material 
can be performed in one operation in the field during use for harvesting 
frown mowing to storing (e.g., in a silo) of the pressed pellets. 
Even though a harvester with a mowing device for straw material (hay) and 
with a pickup device with forced feeding of the mown material via a feed 
screw to a pelletizing device, whose pressing tools were mentioned, has 
been known from the above-mentioned U.S. Pat. No. 3,192,881, the waste 
heat of the internal combustion engine is used to heat the feed means for 
the straw material, whereas a separate heat source must be installed for 
heating the pressing members of the pelletizing device. 
In contrast, the webs according to the present invention are heated 
preferably by the exhaust gases of the internal combustion engine 
preferably to a temperature higher than 150.degree. C. and especially 
165.degree. C. The straw material can be processed best when it has a 
moisture content of 16-18%. If the moisture content in the harvested 
material is lower than these values, it is advisable to add moisture to 
the straw material on its way to the pellet mill. 
The geometry of the webs and shafts according to the present invention 
including providing the radial length of the webs substantially greater 
than the depth of penetration of the webs into the associated shaft, 
providing that the web front areas penetrate into the shafts in a 
contactless manner and providing an outer front area of the webs with a 
wear bar which is detachably connected provides additional advantages. 
Other features of the webs including the shape of the webs offer the 
advantage that the compaction and the residence time of the straw material 
in the shafts can be performed in an optimized manner. What is achieved is 
first of all that the pressed material is exposed to a defined thermal 
action under reduced friction, and thus it acquires properties important 
for its use as a fuel. represented as examples in the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a self-propelled harvester, which can be steered from a 
driver's cabin (1), whose wheels (3) are driven by an internal combustion 
engine (5). At its front end, the harvester carries a mowing tool (7), 
e.g., a rotary mowing tool with coarse crushing devices, which cuts and 
crushes the straw material being harvested. A slope conveyor (9) transfers 
the coarsely crushed straw material to a vertical conveyor (11), which 
feeds it to a guide roller (13) of a fine crushing mechanism, which [guide 
roller] is arranged in the upper area of the harvester. The said guide 
roller (13) transfers the finely crushed straw material to a trough screw 
(15), which is joined by a pressure worm (17). The outlet of the said 
pressure worm (17) opens into a pelletizing device (19), which will be 
explained in greater detail below, and which compresses the straw material 
precompacted by the said pressure worm (17) into free-flowing pellets. The 
said pelletizing device (19) is arranged above a silo (21), which is 
arranged in the rear area of the harvester and receives the pellets. 
The said pelletizing device (see FIGS. 2 and 3) comprises two pelletizing 
bodies, which are mounted in parallel to one another, are designed as 
hollow rolls (33), have webs and shafts engaging each other on their 
circumference, and are heated via a heating circuit by the waste heat of 
the said internal combustion engine (5) to at least 100.degree. C., but 
preferably to a temperature higher than 150.degree. C. The heating circuit 
comprises in this example a heat exchanger (23) connected to the coolant 
circuit of the said internal combustion engine, or it forms as such the 
coolant circuit and it is connected via connection lines (25) to heating 
agent channels of the pelletizing bodies, which will be explained in 
greater detail below. The waste heat of the said internal combustion 
engine (5) can thus be recovered, which considerably improves the overall 
efficiency of the harvester. The said internal combustion engine (5) 
drives not only the said wheels (3) of the harvester, but at least also 
the pelletizing bodies of the said pelletizing device (19) and, if 
desired, also the said rotary mowing tool (7), including the said 
conveyers (9) through (17). 
A substantial increase in the efficiency of the entire unit is achieved 
when the exhaust gases of the said internal combustion engine (5) are used 
to heat the said pelletizing device. Without additional energy supply, it 
is thus possible to achieve heating of the pressing elements to ca. 
165.degree. C., which has proved to be optimal for the pressing operation. 
It is therefore obvious that other heat exchangers may additionally be 
provided, if desired, to recover heat from other waste heat sources of the 
said internal combustion engine, in addition to or instead of the said 
heat exchanger (23) connected to the cooling circuit of the said internal 
combustion engine (5). 
FIG. 14 shows a harvester (2), which is an alternative to the said 
harvester shown in FIG. 1, and which can be steered from the said drive's 
cabin (1) and is driven by a said internal combustion engine (5). At its 
front end, the said harvester carries a pickup device (4) for straw 
material, a side feed screw (6), which is arranged at the top and is 
offset to the rear in the direction of travel and consists of a pipe with 
two worm brushes, which feed the material picked up to the middle. The 
material is grasped by controlled feed prongs (8) there, fed into the 
intake area (10) of a pressing device (12), and crushed at the cutting 
knives (14) extending into the feed path in the process. 
The use of a pelletizing device, consisting of two hollow rolls (33) 
arranged axially in parallel to one another (see FIG. 5), is schematically 
represented in the drawing as the said pressing device (12). However, it 
is also possible to use a screw-type compactor. 
The pellets or pressed objects are fed with an elevator (16) into a said 
silo (21). 
The arrangement of the pressing device directly behind a pick-up device or 
a mowing device for the material to be pressed is also of independent 
inventive significance if the pressing device is not designed as a 
replaceable structural unit, because it is advantageous for the work 
process to compact the material to be pressed immediately after pickup and 
thus to maintain a short feed path for the material of low density. 
FIGS. 2 and 3 show details of the said pelletizing device (19). The 
pelletizing bodies have the shape of two hollow rolls (33), which are 
mounted rotatably axially in parallel to one another in bearings (29, 31) 
in a housing (27), and which are driven by a drive shaft (37) via a gear 
mechanism (35) to rotate in opposite directions. 
The hollow wheels (33) have a plurality of webs (39), which have a flat 
axial longitudinal section and enclose a hollow space (41). The said webs 
(39) are axially located, detachably fastened, between a plate-shaped 
flange body (43), which in turn is held on an axle journal (45) connected 
to the transmission (35), and, on the other hand, an annular flange body 
(49), which surrounds an outlet opening (47). In the circumferential 
direction, adjacent webs (39) define a pressing chamber (shaft) (51), 
which tapers approximately in a wedge-shaped pattern toward the hollow 
space (41) and passes through continuously from the outer circumference to 
the inner circumference of the circumferential wall. The radially outer 
end areas of the said webs (39) of the respective other hollow roll, 
acting as an extrusion die, engage the said shafts (51), which have an 
elongated rectangular cross section, while the said hollow rolls (33) 
rotate in opposite directions. Straw material forcibly fed into and 
crushed in the roll gap of the said hollow rolls (33) by the said pressure 
worm (17) is pressed into the said shafts (51) by the said webs (39), and 
it is compacted there. The dimension of the said webs (39) is selected to 
be such that they engage the said shafts (51) with a clearance, i.e., they 
do not touch each other, while the said hollow wheels (33) are forcibly 
driven via the said transmission (35) in relation to one another. 
Centrally arranged crushing cones (53), which taper toward the said outlet 
opening (47) and crush the pressed strands leaving the said shafts (51) 
radially in the inward direction into pellets and deflect them to the said 
outlet opening (47), are seated inside the said hollow spaces (41), whose 
axial depth relative to the axial length of the said webs (39), is smaller 
than their internal diameter. This action is reinforced by radial guide 
plates (55) (FIG. 2), which extend the said webs (39) toward the said 
crushing cone (53). The said hollow rolls are arranged in this example 
with a said downwardly directed outlet opening (47), so that the crushed 
pellets can immediately fall into the said silo (21) (FIG. 1). 
As is shown best by FIG. 3, the said webs (39) have heating agent channels 
(57), which are connected via the said flange body (43) and the said axle 
journal (45) to a rotary liquid coupling (59), to which the said heating 
agent lines (25) are connected. A liquid heat carrier medium, e.g., in the 
form of a heat-resistant oil or the like, which is heated by the said heat 
exchanger (23) of the said internal combustion engine (5) to at least 
150.degree. C., circulates in the said heating agent channels (57). 
Keeping the straw material to be pelletized at an increased temperature in 
the said shafts (51) reduces the drive output needed to drive the said 
hollow rolls (33) and reduces the pressure needed for compaction in the 
said shafts (51). It is obvious that a heat pump may be connected into the 
heating agent circuit, if desired, should the temperature level supplied 
by the said internal combustion engine (5) be too low. In addition to the 
said heating agent channels (57), additional heating agent channels (65) 
(FIG. 1), which are connected to the said heat exchanger (23), are also 
provided in the housing (61) of the said pressure worm (17) forming the 
feed path, as well as in the areas (63) of the said housing (27) which 
closely surround the said feed path. The said heating agent channels (65) 
in the said housing walls (63) or in the said housing pipe (61) may be 
omitted, if desired. If the heating capacity of the said heating agent 
channels (65) is sufficient in itself, the said heating agent channels 
(57) of the said hollow rolls (33) may possibly be omitted as well. 
Two respective repressing rollers (67) and (69) mounted rotatably in the 
said housing (27) axially in parallel to the said hollow rolls (33) may be 
associated with each of the said two hollow rolls (33) in order to improve 
the pressing action. Contrary to the said hollow rolls (33), the said 
repressing rollers (67, 69) have only radially projecting dies (71), which 
engage the said shafts (51) of the said associated hollow roll (33). The 
said repressing rollers (67, 69) consecutively mesh with the said 
associated hollow roll (33), and the depth of penetration of the said dies 
(71) increases in the repressing rollers following each other in the 
direction of rotation (73) of the said hollow rolls. The different depth 
of penetration of the said dies (71) can be achieved by different die 
heights and/or a different axial distance between the said repressing 
rollers and the said hollow rolls. The said repressing rollers (67, 69) 
may be driven loosely by the meshing of the said dies (71); however, they 
may also be forcibly synchronized with the said transmission (35). 
To make it possible to adjust the depth of penetration of the said webs 
(39) into the said shafts (51), the said housing (27) is divided, at right 
angles to the connection plane of the hollow roll axes, into two housing 
halves (75), on which one of the said hollow rolls (33) each, including 
the associated repressing rollers (67, 69), is mounted. The said housing 
halves (75) are adjustable in relation to one another in the direction of 
the connection plane of the axes. The adjusting movement is preferably 
performed around the axis of rotation of one of the gears of the said 
transmission (35) in order to maintain the meshing of the teeth 
independently from the adjusted position. It is obvious that other drive 
chains which ensure the forced engagement of the said hollow rolls, e.g., 
in the form of link chains or toothed belts, may be used as well. 
The feed capacity of the said pressure worm (17) is preferably adjustable, 
e.g., by varying the worm speed, in order to ensure a uniform and optimal 
feeding of the said hollow rolls (33) with material to be pelletized. The 
worm speed is preferably maintained at a constant set value via a control 
loop depending on the drive output of the said hollow rolls (33). 
A continuously variable, controllable transmission may be provided to 
adjust the worm speed. However, the feed capacity of the said pressure 
worm may also be varied in another manner, e.g., by using an axially 
adjustable conical worm in a conical housing. 
It is obvious that heat sources other than the waste heat of the internal 
combustion engine of a harvester may also be used in the exemplary 
embodiments of the pelletizing devices and of the pressing device 
explained above. In addition, it should be pointed out that the mechanical 
design of the pelletizing devices according to FIGS. 2 and 3 may also be 
used, in a particular case, without heating devices for heating the 
pressing channels. 
The exemplary embodiment according to FIGS. 5 through 11 shows a preferred 
design variant for the pelletizing device according to the present 
invention, whose individual features have arisen from practice and from 
the consistent improvement of the object of FIG. 2. 
The said housing (27) of the pelletizing device has a housing frame (28) 
and a housing shell (30). The said housing shell (30) surrounds both said 
hollow bodies (33) with a substantially smaller clearance than is 
represented in FIG. 2. The material to be pelletized is force-fed in the 
crushed state into the wedge area of the said hollow rolls (33) via a 
housing connection (32). The said housing connection (32) has a hollow 
space (34) expanding in the shape of a wedge in the direction of feed. In 
the opposite wedge area, a wedge-shaped component (36) is connected to the 
said housing (28, 30), whose outer surface (38) is nearly in sliding 
friction with the outer front areas of the said webs (39). 
It was found to be highly advantageous in practice for the said housing 
shell (30) not be located centrally to the axis of rotation of the said 
webs (39). If the clearance between the inner surface of the said housing 
shell (30) and the outer jacket areas of the said webs (39) is made 
variable, so that a minimum clearance (40) is set in the area of the 
contact point between the said webs (39) and the said wedge-shaped 
component (36), and a maximum clearance (42) is set at the transition of 
the said housing shell (30) to the said housing connection (32), the risk 
of blockage of the rotation of the said hollow bodies (33) in the said 
housing (28, 30) is eliminated. The difference in clearance is relatively 
small; favorable experience was achieved with a difference of 1 mm. 
However, the present invention is not limited to this measure. 
The representation on a larger scale in FIG. 6 shows that a worm housing 
(44), which is formed of a hollow space (46) tapering in the direction of 
feed of the material to be pelletized, is located adjacent to the said 
housing connection (32). The said pressure worm (48) guided in it is 
correspondingly wedge-shaped as well, as is apparent from FIG. 4. 
Not only forced feeding of the straw material to be pelletized is achieved 
with this measure, but a considerable feed pressure, which forces the 
material located in the said hollow space (34) to penetrate into the said 
shafts (51), is achieved as well. 
In addition, it is clearly recognizable that the radial length of the said 
webs (39) and consequently also the radial length of the said shafts (51) 
located between them are substantially greater than the average thickness 
of the said webs (39) and of the said shafts (51). It can also be seen in 
FIG. 8 that the depth of penetration (52) of the said webs (39) into the 
said shafts (51) is relatively minimal. 
The geometry of the said webs (39), whose specific design is shown in a 
preferred exemplary embodiment represented in FIG. 7, is such that the web 
edges (70) will not mutually touch each other during engagement. Instead, 
a small clearance is intentionally left between the said web edges (70). 
Consequently, the said webs (39) do not roll on one another, as it happens 
according to the state of the art. 
However, the small clearance between the said web edges (70) also causes 
the straw material forcibly fed into their area to be shorn off and to be 
pressed into the said shafts (51) without any residues remaining. 
To absorb the strong forces that occur, the said webs (39) in the exemplary 
embodiment according to FIG. 7 have wear bars (54) on the outer front 
side, which are fastened to the said webs by means of bolts (56). The said 
wear bars (54) are guided in grooves (84) with web projections (90) in 
order to prevent the pressing pressure from acting on the said bolts (56). 
The said wear bar (54) expands in the shape of a parallelepiped at right 
angles to the plane of the drawing sheet. If, e.g., the representation in 
FIG. 10 is assumed to correspond to the actual size of a said web (39), 
the length of the said parallelepipedic wear bar (54) is approximately 100 
mm. 
As a result, a pressing channel (51), which is elongated in the axial 
direction and has an approximately rectangular cross section, is obtained, 
but the said pressing channel may also have a bulged shape. 
The said individual web (39) has different thicknesses in the radial cross 
section according to FIG. 7. An undercut (64) is located opposite a 
wedge-shaped expansion (58) of the said web (39) directly behind the said 
wear bar (54). The said wedge-shaped expansion (58) is joined by an area 
(60) of constant thickness of the said web (39), which may also be 
designed as a slightly wedge-shaped web, after which the said web (39) 
passes over into a wedge-shaped tapered section (62). As is clearly 
apparent from FIGS. 6 and 8, the outer wall surfaces of the said webs (39) 
determine the shape of the said shafts (51) due to their radial 
arrangement on the said hollow body (33). Thus, there is first a slight 
wedge-shaped tapering of the said shafts (51) due to the said wear bars 
(54), and then there is a more intense wedge-shaped tapering of the said 
shafts (51) due to the wedge-shaped expansions (58). The areas (60) of 
constant thickness or of slight wedge-shaped expansion of the said webs 
(39) also lead to a decreasing, wedge-shaped tapering of the said shafts 
(51) in the radial direction as a consequence of the radial arrangement of 
the said webs (39). 
Providing a zone of constant thickness in the area of the transition 
between a wedge-shaped thickening (60) and a wedge-shaped tapering (62) of 
the said web (39) in order to reduce the wear of the web walls at the 
edges of the said transitions has also proved to be advantageous. The said 
zones of constant thickness preferably have a low height of a few mm when 
viewed in the radial direction. 
Whether the said shafts (51) have a constant width or a tapered section in 
the middle and radially inner area is obviously determined by the 
dimension of the said wedge-shaped tapered section (62) of the said webs 
(39). It proved to be advantageous in practice for the said shafts (51) to 
expand in a wedge-shaped pattern radially in the inward direction, while 
the length of the said area (62) of the said web (39) will be greater than 
half the radial length of the said web (39). The resulting expansion of 
the said pressing channel (51), which opens to the inside in a 
wedge-shaped pattern, causes the compacted strand, which slowly advances 
in the said pressing channel (51), not to be exposed to an increasing, but 
rather to a relieving friction, despite the tendency to swell and the 
degassing pressure. 
Finally, FIG. 7 shows that it is recommended that radially inwardly 
extending longitudinal grooves (66) be arranged in the outer wall surfaces 
of the said webs (39). 
The said longitudinal grooves (66) serve the purpose of allowing the gas 
pressure, which greatly increases during the compaction of the straw 
material, to escape. Therefore, the said longitudinal grooves (66) are 
also open on the inner front side. 
A type of barb action, which hinders the material pressed in from exerting 
a considerable radial pressure in the outward direction in terms of a 
pressure relief, is brought about by the said above-mentioned undercut 
(64) between the said wedge-shaped expansion (58) and the said wear bar 
(54). On the other hand, the material pressed into the said pressing 
channel (51) is deflected by the said bevels (58) into a direction 
deviating from the radial direction, which leads to an arrow-like layer 
formation in the strand. If the pressed material is to be used as fuel, 
this offers the advantage that the individual pressed body will expand 
more readily under the action of heat, develops a larger surface offering 
access to oxygen, and thus leads to a higher heating efficiency. 
All the measures described ultimately lead to the maintenance of the lowest 
possible friction between the material being guided in the pressed form 
through the said shafts (51) and the outer walls of the said webs (39), 
which contributes to achieving the maximum material throughput at a 
minimum energy consumption. It is therefore also recommended to design the 
outer surfaces of the said webs (39) with the lowest friction possible. As 
was described above in connection with FIGS. 2 and 3, the holes extending 
in the said webs (39) in parallel to the axis of rotation of the said 
hollow bodies (33) are intended to feed a heating agent to the immediate 
vicinity of the pressing members. Efficiency is optimal if the said webs 
are heated to temperatures higher than 150.degree. C. and especially in 
the range of 165.degree. C. 
It was found in practice that the best pressing effect can be achieved when 
the exhaust gases of the said internal combustion engine (5) are passed 
through the said holes (72). Heating of the said webs (39) to 
approximately 165.degree. C. can thus be achieved without the use of a 
separate heat source 
Based on a design of the said webs (39) corresponding to FIGS. 7 and 8, the 
compaction of the straw material is complete as soon as the material 
located in the said shafts (51) reaches the inner end of the said area 
(60) of constant web thickness. Nevertheless, the said webs (39) extend 
much longer in the radial direction, even though no more compaction is 
intended due to the said wedge-shaped tapered section (62) of the said 
webs (39). 
The purpose of this measure is to ensure a longer residence time for the 
pressed straw material in the said shaft (51) and thus to initiate the 
hardening of the material. However, this prolonged residence time must not 
lead to an increase in resistance, and the said wedge-shaped tapered 
section (62) and smoothing of the surface of the sid webs (39) is 
therefore preferred. The said longitudinal grooves (66) also make a 
substantial contribution to degassing and consequently to the reduction of 
friction. 
Based on these considerations, the ratio of the said depth of penetration 
(52) of the said webs (39) or of the said wear bars (54) to the radial 
length of the said webs (39) is extremely different from the state of the 
art. The present invention proposed that this ratio be selected on the 
order of magnitude of more than 1:8 and especially in the range of 1:10 to 
1:25. 
The present invention also shows that the residence time of the pressed 
material in the shaft can also be optimized by reducing the flow rate of 
the heating medium in the said holes (72) of the said webs (39). This can 
be achieved by introducing, e.g., coils (77) or other flow obstacles into 
the said holes (72), as is shown in the example represented in FIGS. 7 and 
13. 
FIGS. 9 through 11 show details of how the said webs (39) according to FIG. 
7 can be connected to the said flange bodies (43) of the said hollow rolls 
(33), so that the possibility of replacement of the said webs is 
guaranteed, on the one hand, and, on the other hand, the especially strong 
forces occurring during pressing can be absorbed without the risk of 
breakage. 
FIG. 9 shows in this connection the front view of a partial area of a cheek 
(74) of the said individual flange body (43). The said cheek (74) has 
regularly distributed recesses or perforations (76), which are intended to 
accommodate a said web (39) each, and possibly even a pair of adjacent 
webs (39), as is shown in FIG. 10. Thus, the edges (78) of the said 
recesses (76) determine the radial position of the said individual web 
(39), which is secured in this position against the said edges (78) by 
wedging by means of a strip (80) each. As is shown in FIG. 10, the said 
strip (80) needs to be fastened to the said cheek only with a bolt (82). 
On their lateral wall surfaces, the said webs (39) have radially extending, 
groove-like milled slots (92), which are located directly opposite the 
said strips (80) in the installed state. Due to the profiling of the 
lateral wall surfaces of the said webs (39), the said milled slots (92) 
are present in some areas only. The said strips (80) engage the said 
milled slots (92) and thus form axially parallel stops on both sides of 
the said cheeks (74), thus preventing an axial mobility of the said webs 
(39) in the said cheeks (74). 
As is also apparent from FIG. 10, the said wear bars (54) extend radially 
beyond the outer circumference of the said cheek (74). 
As is apparent from the top view in FIG. 11, the said wear bars (54) have 
only a length corresponding to the distance of the said cheeks (74). This 
results in stops (88) which also bring about fixation of the said webs 
along the axis of the said hollow bodies (33) in relation to the said 
cheeks (74) of the said flange bodies (43, 49) as a consequence of the 
bolt connection (56) of the said wear bars (54) to the said webs (39). 
Finally, the said webs (39) project with the projecting areas (86) above 
the outer surfaces of the said cheeks (74), which serves the purpose of 
enabling the said strips (80) to be arranged on the outside of the said 
cheeks (74) for wedging the said webs (39) and for acting against the said 
projecting areas (86). 
As is shown in FIG. 12, the pelletizing device according to the present 
invention may also be arranged stationarily, instead of on a harvesting 
vehicle. The design of the said hollow rolls (33) corresponds to the 
exemplary embodiment according to FIG. 5. The said housing (27), not 
shown, may be arranged stationarily. 
An electric motor (20), which drives a feed screw analogous to (15) in FIG. 
1, is arranged on a movable frame (18). The straw material, which has been 
transported from the field and may have been crushed, is fed into the said 
conical worm housing (44) (cf. FIG. 6), in which a conical worm (48) for 
the forced transfer of the straw material to the said hollow rolls (33) is 
located. 
Strippers (26), which act against the inner edges of the said webs (39) in 
the manner of a wiping blade and break off the compacted strands of straw 
material being discharged there, are located in the said hollow spaces 
(41) of the said hollow rolls (33). 
If greater lengths of broken-off pressed bodies are desirable, the said 
stripper (26) must be brought out of the wiping position for a selectable 
period of time. This can be achieved, e.g., with an adjusting axle (24), 
to which the said stripper (26) is fastened. The distance between the said 
stripper (26) and the inner edge of the said webs (39) can be changed by 
rotating the said axle. 
The exemplary embodiment according to FIG. 13 shows, contrary to FIG. 3, a 
canthever mounting (79) of the said hollow bodies (33). The said 
bearing-side flange body (43) is rigidly connected to the said drive shaft 
(45). The said discharge-side flange body (49) is carried by the said 
flange body (43) via the plurality of said webs (39). The said housing 
(27) consists of the said housing frame (28) and the said housing shell 
(30), which are connected to one another via bolts (81) and surround the 
said webs (39). The said webs (39) are joined, on both sides, by chambers 
(83) and (85), which are intended to feed in and remove heating agents. 
For example, exhaust gases of an internal combustion engine can be passed 
through the said holes (72) of the said webs (39) in this simple manner. 
To utilize the heat of the heating agent as completely as possible, it is 
recommended that elements, e.g., coils (77), be arranged in the said holes 
(72) of the said webs (39), which is to reduce the flow rate of the 
heating agent. Such coils (77) in a said hole (72) each are symbolically 
represented in FIGS. 7 and 13. 
FIGS. 15 through 17 are linked with the exemplary embodiment according to 
FIG. 8, and they show an advantageous variant, which is not, however, 
dependent on the cross-sectional shape of the said webs. 
To achieve the highest possible throughput and consequently a high 
efficiency, one seeks to maintain the length of the said webs (39) and 
consequently that of the said pressing channels (51), viewed in the axial 
direction of the said hollow rolls (33), as long as possible. Relatively 
broad strands will leave the said pressing channels (51) in this case, and 
when they are broken off, a granule size advantageous for the further 
processing is not necessarily ensured. 
Therefore, the example according to FIGS. 16 through 18 shows that the said 
pressing channels (51) are divided by partitions (83), which extend in 
radial planes in relation to the axis of the said hollow rolls (33) and 
pass transversely through the said pressing channels (51). 
As can be recognized from FIG. 15, the said individual partition (83) has a 
wedge shape tapering from the outside to the inside in the axial view. As 
can be recognized from the representations in FIGS. 16 and 17, the cross 
section of the said partition (83) is prismatic, and especially 
rectangular. This makes it possible to guide the said partition (83) in 
grooves (87) of the said webs (39), which are located opposite each other. 
It is shown in the example represented in FIG. 16 that the said individual 
pressing channel (51) may be divided either by a said single partition 
(83) or by two or more said partitions (83). FIG. 16 also shows 
symbolically that the said webs (39) are guided in the said flange bodies 
(43, 49), which form the said hollow rolls (33) together with the said 
webs (39). 
In the outer front area, the said individual partition (83) has a 
preferably ridge-like cutting edge (85), which may be formed by beveling 
the said partition (83) corresponding to the exemplary embodiment shown in 
FIG. 17. The said cutting edge (85) has the task of reducing the 
resistance of the said partition (83) to the pressing pressure which is 
generated by the said individual webs (39) during the stuffing of the 
vegetable material into the said pressing channels (51). A division of the 
said pressing channels (51) and consequently of the strands compacted into 
the said pressing channels (51) is thus achieved, which leads to a 
reduction in the width of the granules to be formed. 
The position of the said individual partition (83) must be secured in order 
to prevent it from becoming mobile under the influence of the pressing 
pressure. To achieve this, the said individual partition has hammer 
head-like projections (89), which engage grooves (91) of the said webs 
(39) (compare FIG. 15). The said grooves extend in the circumferential 
direction in relation to the movement of the said webs (39). The said 
individual partition (83) is consequently supported on the bottom of the 
said groove (91) under the effect of the pressing pressure. In the other 
direction, the said partition (83) or the said individual hammer head-like 
projection (89) is decelerated by a stop surface (93) of a said wear bar 
(54), which forms the actual cutting edges of the said web (39). As is 
shown in FIG. 17, the said wear bars (54) are attached to the front 
surfaces of the said webs (39) by means of bolts (94). 
The insertion and removal of the said individual partitions (83) is thus 
facilitated, because only the said wear bars (54) are to be bolted on. 
As is shown in FIG. 16, the said cutting edge (85) extends only between the 
side surfaces of the said wear bars (54) facing each other. Lateral 
channels are thus prevented from being formed due to the bevel along the 
stop surface. The said cutting edge (85) is aligned with the laterally 
adjacent front surfaces of the said partition (83). 
FIG. 18 shows symbolically a grinding device (96), which can be moved to 
and fro in parallel to the axis of the said individual hollow roll (33) 
and consequently along the said cutting edge (70) of the said individual 
web (39) or its said wear bar (54). To achieve this, a grinding roller 
(98), driven to perform rotary movements, is occasionally moved to and fro 
along the arrow (99) on an axially parallel axis (97). The said grinding 
roller smoothes the circumferential surface of the said wear bar (54) and 
thus sharpens the said cutting edge or web edge (70). 
LIST OF REFERENCE NUMERALS 
1 Driver's cabin 
2 Harvester 
3 Wheel 
4 Pickup device 
5 Internal combustion engine 
6 Side feed screw 
7 Mowing tool 
8 Feed prongs 
9 Slope conveyor 
10 Intake area 
11 Vertical conveyor 
12 Pressing device 
13 Fine crushing mechanism (guide roller) 
14 Cutting knife 
15 Trough screw 
16 Elevator 
17 Pressure worm 
18 Frame 
19 Pelletizing device 
20 Electric motor 
21 Silo 
23 Heat exchanger 
24 Adjusting axle 
25 Connection line 
26 Stripper 
27 Housing 
28 Housing frame 
29 Bearing 
30 Housing shell 
31 Bearing 
32 Housing connection 
33 Hollow roll (hollow wheel) 
34 Hollow space expanding in the shape of a wedge 
35 Gear transmission 
36 Wedge-shaped component 
37 Drive shaft 
38 Outer surface 
39 Web 
40 Minimum clearance 
41 Hollow space 
42 Maximum clearance 
43 Flange body 
44 Worm housing 
45 Axle journal 
46 Hollow space tapering in the shape of a wedge 
47 Outlet opening 
48 Wedge-shaped pressure worm 
49 Flange body 
50 Radial length 
51 Pressing channel (shaft) 
52 Depth of penetration 
53 Crushing cone 
54 Wear bar 
55 Radial guide plate 
56 Bolt 
57 Heating agent channel 
58 Wedge-shaped expansion 
59 Rotary liquid coupling 
60 Area of constant thickness 
61 Housing 
62 Wedge-shaped tapered section 
63 Housing area 
64 Undercut 
65 Heating agent channel 
66 Longitudinal groove 
67 Repressing roller 
68 Open outlet 
69 Repressing roller 
70 Web edge 
71 Die 
72 Heating agent hole 
73 Direction of rotation 
74 Cheek of flange body 
75 Housing halves 
76 Recess 
77 Coil 
78 Edge 
79 Canthever mounting 
80 Strip 
81 Bolt 
82 Screw 
83 Partition 
84 Groove 
85 Cutting edge 
86 Projecting area 
87 Groove 
88 Stop 
89 Hammer head-like projection 
90 Web projection 
91 Groove 
92 Milled slot 
93 Stop surface 
94 Screw 
95 Arrow 
96 Grinding device 
97 Axis 
98 Grinding roller 
99 Arrow 
131 Housing 
133 Conical pressing space 
135 Conical worm 
137 Worm outlet 
139 Die pipe 
143 Heating agent channel