Note: Descriptions are shown in the official language in which they were submitted.
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Machine fog extruding concrete elements.
The present invention relates to a machine for extruding reinforced
elements in concrete, particularly hollow reinforced concrete elements and
slabs.
Such extruding machines usually include a moveable frame or carriage
which in front has an operational unit, thereafter an open feeding hopper unit
for
supply of fresh concrete which opens down into a horizontally backwardly
extending feeding chamber for concrete, one through the feeding chamber
stafiionary arranged support shaft for a rotating feeding screw which at the
to downstream end extends outwards into a forming tube in order to provide
openings or voids in the extruded concrete element. The machine is furthermore
provided with a number of vibrators, at least one of which is positioned on
the top
of the feeding chamber, and one inside each of the forming tubes. The machine
is
mounted on a casting floor or so called steel bench. In use the concrete mass
is
is pressed from the feeding screws into and round the forming tube and from
there
out on the supporting base or stratum, simultaneously as the casting machine
is
pressed or moved forwards with suitable velocity, for instance one meter per
minute,
In order to accomplish a satisfactory production of hollow elements using a
Zo such machine it is, firstly, necessary to use fresh concrete with
relatively law water
content) usually so called «soil moisty» concrete without slump. Further one
must
utilize high feeding pressure on the screw) and high vibration during the
compacting and feeding of the fresh or raw concrete, such that the concrete
attains sufficient liquid state. The moulding or extruding machine usually
inqludes
Zs a number of side by side arranged forming tubes wifih separate equipment
for
producing hollow elements with the required number of throughgoing openings.
Known machines of this type make in general satisfactory products but
exhibit still several shortcomings. A substantial shortcoming is that the
vibrators
produce high noise with a noise i~vel above 100 decibels. Powerful vibration
is
so however necessary in order to provide the necessary float in the concrete
mass.
The vibrators are usually driven with rotational speed of 10.-12.000 rpm. Not
only
causes such noise a large problem for the operators in the production
premises,
but subjects also the machine elements to large wear and necessitafies
frequent
prod~:ction shut-downs for rtiaintenance and replacement of parts.
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The inventor has studied this problem and has realized xhat a substantial
part of the noise originates from the fact that the vibrator means are
positioned
adjacent the forming tube such that the vibrations to all surrounding machine
parts, through the compacted concrete, through the rigid support shaft and fo
the
remaining parts of the machine will all result in a very high noise level.
A substantial part of these problems is solved through the present invention
which is generally characterized in that the vibrator device positioned in
connection with the forming tube is mounted in an elastic suspension which is
mechanically separated from the forwardly positioned stationary shaft
supporting
io the rotating feeding screw.
In a preferred embodiment of the invention the forming tube is together with
the vibrator mounted on an elastic body which in front is fastened to the
stationary
shaft.
Through this solution the forming tube is floating freely inside the concrete
~s mass and the vibration energy will migrate directly into the concrete mass
and is
not directly conveyed to the surrounding machine parts. Thereby the origin for
vibrational noise is radically reduced, simultaneously as the need for
vibration
power may be reduced. The invention thus results both in reduced noise and
less
wear.
2o An embodiment of the invention shall be described further with reference to
the accompanying drawings, wherein
fig, 1 shows a longitudinal schematic section through an extruding machine
of in per se known art and wherein the invention is included in the actual
parts of
the machine, more particularly in the forming tube)
2s fig. 2 shows two embodiments of hollow slabs of the kind produced rrvith
the
machine,
fig, 3 shows a longitudinal, schematic drawing, partly in section)
illustrating
the vital parts in a known machine, and ~Nhich illustrates the usual way of
mounting the vibrator in the forming tube, and
3o fig. 4 shows a somewhat enlarged corresponding longitudinal section and
which further illustrates the solution in accordance with the invention.
Fig. 1 shows a complete extruding machine comprising a driving unit 1
running on front wheels 2 and rear wheels 4 on a floor or so called steel
bench 6,
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At the ftont of the driving unit is mounted a drive unit 8, at the rear end of
which is
mounted a container or open hopper 10, opening down into a horizontal feeding
chamber 12, wherethrough is running a mandrel 14 which is supported on a
stationary shaft 16 which further is supported in a bearing house 18. At the
rear
s end of the stationary shaft 16 is mounted a stationary forming tube 20 which
envelopes the vibrator unit 22. On the top side of the feeding chamber above
the
forming tube is usually positioned a vibrator plate 24. It will be understood
that all
parts of the extruding machine which are in contact with the concrete are
stationary, disregarding the rotating feeding screw 14, which is supported on
the
io support shaft 16. The machine is provided with a number of side by side
situated
feeding chambers with separate feeding screws for making hollow stabs as shown
in fig. 2.
In use fresh concrete is poured down into the container 10 from where it
falls down into the feeding chamber 12 and is screwed backwards by means of
is the feeding screw 14, simultaneously as the concrete is compressed
simultaneously as it is vibrated. At the rear end of the feeding screw the
concrete
is circumferentially distributed around the forming tube 20 subject to strong
vibration, simultaneously as the entire extruding machine in result of the
pressure
from the feeding screw is being moved forward with desired velocity,
ao simultaneously as the extruded hollow element or slab is left behind on the
substrate shown at the reference number ZB to the right side of fig. 1. On the
fop
side is positioned finishing plate 27,
The internal parts of the machine at a known extruder embodiment are
shown in Fig. 4 in dE 20 59 760 C2 and ~s schematically illustrated on fig. 3.
zs Herein the feeding screw 30 is supported on a hollow support shaft 32. The
feeding screw 30 is at the front end provided with gear drive 34 connected to
a
motor drive 35. The forming tube 36 comprises in this embodiment two parts,
namely a rear part 36 which via an elastic coupling 38 is connected to a front
part
40 of the forming tube, and which in the front side is mounted on a support
disc
30 42) attached to the rear end of the stationary shaft 32. Inside the front
part 40 of
the forming tube 38 is mounted a vibrator 44 on a longitudinal shaft 46
extending
through the hollow stationary shaft 32 and which in front is connected to an
electric motor 48. The construction shown in fig. 3 has proved to generate
noise
on a very high level since a substantial part of the vibrations will migrate
to the
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support disc 42 at the rear end of the stationary shaft, and from there
further to
the machine parts. Simultaneously a correspondingly smaller part of the
vibration
energy will migrate radially outwards to the concrete mass which surrounds the
forming tube 36, 40 such as illustrated in fig. 1.
The reference number 7 in figs. 1 and 2 designates tension or stretching
cables which are introduced on the bottom side of the slabs by means of not
shown, knows equipment.
Fig. 4 shows a longitudinal view similar to fig. 3 through the internal parts
of
a machine in accordance with the invention. The section shown in fg. 4
o constitutes substantially enlargements of the corresponding parts shown in
fig. 1.
and the same reference numbers are utilized on the same parts. The forming
tube
20 is in accordance with the invention mounted on an elastic transition member
50, the front side of which is attached on a support disc 52 and which in
accordance with the invention suitably is provided with a radial widening in
~s direction rearwards, such that the circumference at this end runs flush
with tie
outside of the elastic dampening member 50, which have the same outside
diameter as the forming tube 20 (shown stitched). The vibrator device in
accordance with the invention consists suitably of an elongated body 22 which
extends coaxially through the forming tube 20, and at the rear end is
supported via
2o a support pin 56 in the transverse wall 58 on the forming tube) and the
foreend of
which in similar manner is mounted on a transverse wall 60 on the forming tube
via a support pin 62. The vibrator device itself includes an eccenter 6A~
positioned
at the front end in the vibrator body so close to the foreend of the forming
tube 20
as possible. The vibrator is preferably electrically driven and is receiving
electric
2s power through a cable 66 which is passed through the hollow support shaft 1
B. By
positioning the vibrator with eccenter as close to the elastic dampening
member
50 as possible, optimal vibration is provided on the concrete mass positioned
outside the forming tube. The forming tube will in this fashion obtain a
floating
suspension inside the rearwardly directed extrusion chamber, a fact which is
also
3o rather favourable with the aim to obtain even compression or compacting of
the
concrete mass. The arrows 70 in fig. 4 illustrates the vipration pattern,
namely
such that optimal vibration will be situated at the tore end of the forming
tube
behind the dampening member 50 and with gradually reduced vibrations to a zero
towards the rear end of the forming tube, a fact which is very desirable in
order to
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avoid sink in the concrete mass which otherwise may cause deformed hollow
openings through the hollow element or slab.
An extruding machine in accordance with the invention has proved to result
in a reduction of the noise leve) from 100-110 decibel down to a noise level
of 80-
s 90 decibel or lower. This implies in reality that the practical noise level
with a
machine in accordance with the invention only is a fraction of the noise Level
experienced with known machines, It can be informed that the maximum permitted
noise level in production premises in Norway with the use of hearing
protection
means is stipulated just at 80-90 decibel while a noise level of or above 100
to usually is not permitted on premises staffed with operators in close
vicinity of the
machine. Tryouts have furthermore shown that with existing machines operating
with satisfactory vibration the vibrators must be driven with a speed up to
12000
rpm, while a machine in accordance with the invention may utilize vibrators
With
vibration velocity down to 6000 rpm with correspondingly further r~duction of
the
~s noise level and wear on the machine.
V1/ith known machine today the vibrators cause rather large weer on the
machine parts such that for instance the bearings must be replaced frequently.
