[0001] The present invention relates to a machine for the compression of a bulky mass,
so as to form an elongated, densely-packed body, this machine having a space conically
tapering towards an outlet opening and a driven screw arrangement arranged centrally
in the space.
[0002] Every year several thousands of tons of combustible industrial waste are produced
whose only extractable economic value rests in the possibility of utilizing as large
a part as possible of its latent energy content by means of combustion, for example,
for heating purposes. In order to make such a recovery of energyat all possible it
is necessary many times though to subject the waste to some type of processing which
means in principle that, after sorting out the inferior material, the remaining, more
combustion-effective material is converted to a final form suitable for combustion,
e.g. so-called fuel briquettes. This conversion of form or compression usually takes
place with the help of a machine of the type which has been described above and which
thus consists of a rotating screw located centrally in a conically tapering machine
space, with the help of which the refuse is pressed in form of a helical line through
the space, with successive compression, so as to form an elongated, well-integrated
and form-stable fuel body which subsequently is cut up to the final briquette shape.
[0003] The known machine described here functions well in association with waste of a more
or less easily sliding character, rarely or never, on the other hand, with dry bulky
refuse masses of the type of waste paper, especially plastic-coated waste paper of
the type which occurs in the manufacture of packing laminate for so-called non-returnable
packages for fluid contents. The only possibility of converting such dry paper waste
to effective form-stable fuel briquettes with the help of the known machine of the
screw type has been, therefore, either to eke outthe paper with waste material of
the more easily sliding kind and/or to add water in order to wet and thereby soften
up the paper and transform it into a more appropriate and easily processable consistency.
Such necessary measures involved, however, a worsened heat economy, owing to the additional
blending material as a rule being less combustion-effective than the "pure" waste
paper, whilst any transformation of consistency with the help of water usually required
a subsequent energy-consuming heat treatment in order to dry the moist fuel body formed.
[0004] It is an object of the present invention, therefore, to provide a machine of the
type as described above, but which in contrast to the known machine permits an effective
compression of combustible, bulky refuse, especially plastic-coated waste paper, without
the previously necessary energy-impairing pretreatment of the refuse material.
[0005] This object is achieved in accordance with the present invention in that the machine
described in the introduction has been given the characteristics specified in the
claims.
[0006] The invention will be explained and described in more detail in the following with
reference to the attached drawing which schematically shows a very simple, but practical
and well-functioning embodiment of the machine in accordance with the invention for
the manufacture of form-stable fuel bodies from combustible, bulky refuse material,
especially plastic-coated waste paper.
[0007] On the drawing is thus shown a machine, which has been given the general reference
designation 1, in accordance with the present invention for the compression of a bulky
mass of combustible, dry refuse material 2 which in the example described here is
assumed to be plastic-coated waste paper. The machine 1 comprises mainly three machine
sections, namely a feed-in section 3, an active working section 4 and a feed-out section
5, which are joined together to a machine unit which may be supported on a stand 6.
The feed-in section 3 of the machine 1 comprises a box 9 open at the top which is
limited by a horizontal bottom wall 7 and substantially vertical side walls 8 to receive
and collect waste paper 2 supplied from above which is to be compressed. The box 9
is connected through a hole provided in the front (lefthand) side wall 8 of the box
with a conically tapering compression space 10 in a housing body 11 of the active
machine section 4 arranged against this side wall. In the rear (righthand) side wall
8 of the box 9 a corresponding hole is provided for a hollow driving shaft 12 supported
in the hole in a rotatable manner for a feed screw 13 located in the lower part of
the box, which has a rear screw section 13a located wholly in the box 9 with screw
threads 14 of mutually equal pitch, and a front screw section 13b extending at least
partly into the conically tapering space 10 comprising screw threads 16 with a pitch
successively diminishing towards the space 10. Centrally inside the hollow of the
driving shaft 12 is supported in freely rotatable manner a driving shaft 17 for a
compression screw 18 arranged wholly inside the said space 10 in a straight line in
front of the feed screw 13, with screw threads 19 whose pitch decreases successively
towards the outlet opening 20 of the space 10. The driving shafts 12 and 17 can be
driven in a manner known in itself with the help of a suitable gear drive arrangement
by means of one and the same motor (not shown), and in accordance with the invention
it is important here that the transmission of power between the motor and the shafts
12 and 17 is adapted so that they can be driven at speeds of rotation freely adjustable
in relation to each other. Preferably the shaft 17 for the compression screw 18 is
adapted to be driven at twice the number of revolutions as the shaft 12 for the feed
screw 13.
[0008] With the object of facilitating the feed-in of the bulky waste paper 2 into the compression
space 10, this space has a feed-in region 21 facing towards the box 9 with a somewhat
larger taper than the front zone of the space 10, diminishing conically towards a
more acute top angle. Furthermore the space 10 preferably has surface irregularities
promoting the feed of the waste paper 2 in the form, for example, of parallel,longitudinal
grooves or ridges 23 spaced uniformly around the inner wall 22 of the housing body
11 delimiting the space.
[0009] The feed-out section 5 of the machine 1 finally comprises a hollow, mainly cylindrically
shaped housing body 24 arranged against the housing body 11 and located so that the
axial, cylin drical cavity 26 of the housing body 24 constitutes a direct continuation
of the outlet opening 20 of the conical space 10.
[0010] The machine 1 in accordance with the present invention described above operates in
the following manner. With the help of the said motor (which may be a conventional
electric motor of 55 kW with a motor speed of 1470 rpm) the shafts 12 and 17 are driven
via a suitable power transmission arrangement (e.g. a gear drive of known type) so,
that the compression screw 18 is rotated at a speed (e.g. 882 rpm) which is approx.
twice as high or even higher still than the corresponding speed (e.g. 411 rpm) for
the feed screw 13. The bulky paper refuse 2 supplied from the top and collected in
the box 9, which in the present example consists of shredded, or in a similar manner
homogenized, plastic-coated waste paper consequently will be picked up and advanced
in form of a helical line into the space between screw threads 14 of the screw 13
towards, and into, the conical space 10 through the open, wider end of the feed-in
zone 21. Owing to the fact that the free space between the feed screw 13 and the inner
wall of the housing body 11 successively diminishes in the direction in towards the
space 10, because of the conical tapering of the feed-in zone 21,the bulky mass of
paper waste thus fed will be subjected to a certain precompression during the passage
through the feed-in zone 21. This precompression, which mainly implies a squeezing
out of entrained air, is compensated slightly, though, in that the shaft as well as
the pitch of the screw threads 21 of the front screw section 13b located partly within
the feed-in zone 21 taper or decrease respectively in the direction of feed of the
feed screw 13.
[0011] The paper waste thus advanced and precompressed by the feed screw 13 through the
feed-in zone 21 is advanced further through the space 10, with the help of the compression
screw 18 arranged in front of the feed screw 13 and wholly in the conical space 10,
into the cylindrical feed-out cavity 26 of the housing body 24 through the outlet
opening 20.
[0012] Since the quantity of paper which is advanced through the feed-in zone 21 by the
feed screw 13 is greater than the quantity which actually should be received by, and
be advanced through,. the space 10, which successively tapers towards the outlet opening
20, this means consequently that a certain piling up of paper waste fed must occur
in the feed-in zone 21. However, in accordance with the invention this phenomenon
is avoided by virtue of the compression screw 18 being rotated at a higher speed than
the feed screw 13, more particularly at such a speed that the quantity which is advanced
per unit of time by the feed screw 13 exactly matches the quantity per unit of time
which the compression screw 18 at the higher speed is capable of advancing into the
free space between the threads 19 and the inner surface of the housing body 11. This
free space decreases, however, successively towards the outlet opening 20 and during
the advance with the help of the compression screw 18 heat will be generated owing
to inner friction in the paper waste thus advanced. The frictional heat generated
is sufficiently strong for the plastic coating (e.g. polyethylene) on the paper bits
to melt and thereby effect a fusing together of adjoining paper bits, so as to form
an elongated, compressed and, with the help of the paper bits so fused together, form-stable
fuel body which is fed out continuously through the cavity 26 in the housing body
24.
1. A machine for the compression of a bulky mass, so as to form am elongated, densely
packed body, this machine having a space (10) conically tapering towards an outlet
opening (20) and a driven screw arrangement arranged centrally in the space (10),
characterised in that the screw arrangement comprises a rear feed screw (13) with screw threads (16)
and a front compression screw (18) with screw threads (19), that the respective screw
threads (16 and 19) have pitches decreasing towards the outlet opening (20), and that
the two screws (13 and 18) are rotatable at mutually unequal speeds of rotation.
2. A machine in accordance with claim 1, characterized in that the respective speeds of rotation of the screws (13 and 18) are freely adjustable.
3. A machine in accordance with claim 1 or 2, characterized in that the feed screw (13) has on the one hand a rear cylindrical screw section (13a)
located outside the conically tapering space (10) and on the other hand a conically
tapering screw front section (13b) located wholly within this space.
4. A machine in accordance with anyone of the preceding claims. characterized in that the front end of the conically tapering space (10) is connected directly to
a cylindrical outlet duct (26)
