Concrete extrusion machine

An extrusion machine for making hollow elongated articles of concrete has an eccentric compaction disc that reciprocates and rotates to compact and release air from zero slump concrete. The machine avoids having to have a high frequency converter which is both expensive and noisy. At least one extruder screw is provided in the machine to feed concrete and form the elongated article. The screw has a die former at the outlet end to form a cavity in the elongated article. An eccentric compaction disc is positioned between the outlet end of the extruder screw and an input end of the die former, the input end of the die former is eccentric and coplanar with an eccentric disc face mounted for movement in a circular orbital path about the extruder screw axis. The output end of the die former is concentric with the extruder screw axis.

BACKGROUND OF THE INVENTION 
The present invention relates to an extrusion machine for making hollow 
elongated articles of concrete and more specifically to a concrete 
extruder apparatus that provides improved compacting of the concrete 
without undue noise. 
The extruding of concrete by means of one or more extruder screws into an 
elongated article, sometimes referred to as a slab or plank, which has 
hollow cavities therein to provide the minimum amount of concrete to 
provide the required strength, is known. One example of such a forming 
machine is disclosed in U.S. Pat. No. 4,548,565. In this machine, concrete 
is forced through extruder screws onto a deck. The machine has wheels that 
ride on tracks on each side of the deck. As the concrete passes from the 
extruder screws, the machine moves along the tracks, the movement caused 
by the extruding concrete. A non-rotatable forming element or die former 
is provided to form the hollow cavities immediately following the 
downstream end of the extruder screws. Thus the concrete slab is formed 
and slowly hardens on the deck as the machine moves along the tracks. Side 
plates and a top plate are provided to control the external dimensions of 
the slab and the apparatus moves slowly so that the concrete does not 
collapse. In this way, concrete slabs of almost any length can be 
produced. These slabs are later cut by means of a diamond saw into 
required lengths. 
After extrusion and before the concrete hardens, it is necessary to compact 
the concrete and remove any air trapped therein. This is generally 
achieved by vibration. The vibration helps to remove air in the wet 
concrete which rises to the top surface of the slab. It is known to 
provide a vibrator on the top plate of the forming machine. This top plate 
controls the depth of the slab after it has been extruded. A vibrator is 
also provided in or adjacent the die former to compact the concrete and 
release air from the hollows and voids in the concrete. In most of the 
existing concrete extrusion machines it has been found that high frequency 
vibration is required. In order to achieve this a frequency converter is 
positioned on the machine to provide high frequency for motors to rotate 
at high speeds to drive vibrators on the top plate and in the die former. 
In most cases the motors have rotation speeds in the order of 12,000 rpm. 
Whereas this arrangement works well, the converters produce an excessive 
noise causing an unpleasant environment for operators and others. Attempts 
to provide lower vibration frequencies on the top plate of the extrusion 
machine have been partially successful, but lower vibration frequencies on 
the vibrator in the die former has not provided satisfactory compacting of 
the concrete. The die former used in existing machines is a rigid steel 
unit, high frequencies are transmitted through the die former to the 
uncured, zero slump concrete, but low frequency does not provide 
sufficient vibration to fully compact the formed slab. 
A vibration system presently available for die formers includes an 
eccentric weight on a shaft that rotates inside the die former at speeds 
as high as 12,000 rpm. The die former is made from steel and is rigid, 
thus high frequency vibrations are required in order to transmit the 
vibration through the die former to the concrete to provide compaction and 
air release. 
SUMMARY OF THE INVENTION 
It is an aim of the present invention to provide a concrete extrusion 
machine that compacts and releases air from zero slump concrete as the 
machine moves along on tracks with significantly reduced noise emissions. 
This will be achieved by eliminating the noisy and expensive frequency 
converter and high speed motors previously required. It is a further aim 
to provide a die former which is more flexible and has an eccentric entry 
end which follows a circular orbital path. Thus, a vibration or movement 
is provided by the die former itself rather than providing a separate 
vibrator within the die former. 
The present invention provides in an extruder apparatus for making an 
elongated article of concrete, including at least one extruder screw and 
feed means to feed concrete to the extruder screw to form the elongated 
article and move the apparatus along a track, the extruder screw having a 
die former at an outlet end, adapted to form a cavity in the elongated 
article, and a finishing tube at an output end of the die former to 
provide smooth walls in the cavity, the improvement of means for 
compacting the elongated article while being formed, comprising: an 
eccentric compaction disc between the outlet end of the extruder screw and 
an input end of the die former, the disc having a concentric disc face 
adjacent the outlet end of the extruder screw concentric with an extruder 
screw axis, and an eccentric disc face eccentric with the extruder screw 
axis, the input end of the die former being eccentric and coplanar with 
the eccentric disc face, mounted for movement in a circular orbital path 
about the extruder screw axis, the output end of the die former being 
concentric with the extruder screw axis, and means to concurrently rotate 
the disc and cause the input end of the die former to move in the circular 
orbital path.

BEST MODES FOR CARRYING OUT THE INVENTION 
FIG. 1 illustrates an extrusion machine 11 showing a hollow concrete slab 
12 extruded from the machine onto a base and track 14. There is a hopper 
16 through which the concrete is fed to the machine 11 and an electric 
motor 18 to drive the extruder screws. The machine 11 has wheels 24 to 
move the machine 11 on the track 14 in the direction of the arrow as the 
slab 12 is extruded. This is an existing type of machine known in the 
prior art. 
FIG. 2 illustrates the machine of FIG. 1 in somewhat more detail. The 
hopper 16 leads to an extruder screw 26 which has a trough 28 to guide the 
concrete as it is extruded. The extruder screw 26 compacts the concrete as 
it moves towards the outlet end 27. A die former 30 is connected to the 
outlet end 27 of the extruder screw 26, which in turn is connected to a 
finishing tube 32. The extruder screw 28 is driven by the motor 18 as 
shown in FIG. 1 through the chain drives 29 which rotate a chain sprocket 
34. A stationary tubular shaft 36 extends through the extruder screw 26, 
on the extruder screw axis, and is connected to the die former 30 so that 
the die former 30 itself does not rotate. Furthermore, the finishing tube 
32 is attached to the die former 30 therefore it too does not rotate. An 
eccentric weight 38 inside the die former 30 is mounted in bearings 40 and 
driven by shaft 42 from a high speed motor 43 rotating at a speed of 
approximately 12,000 rpm. The eccentric weight 38 causes the die former 30 
to vibrate. The die former 30 itself is not flexibly mounted thus a high 
speed is required to provide a high frequency vibration to the die former 
30. 
The die former 30 has a slightly larger exterior cross-section than that of 
the finishing tube 32 to allow for some contraction as the machine 
advances and the concrete hardens. The speed of the machine 10 is variable 
but is dependent on the cross section of the slab 12 and the materials in 
the concrete mix. When several extruder screws are positioned 
side-by-side, it is necessary to control the feed of concrete through the 
hopper 16 to each screw. In some situations more concrete is needed in the 
end extruder screws to ensure the slab has a consistent thickness across 
the width. 
Above the die former 30, and attached on each side of the machine 11 is a 
top plate 44 which has mounted thereon a vibrator motor 46. The vibrator 
motor rotates at 12,000 rpm and has a small eccentric weight therein to 
provide a similar vibration to the top plate 44 as is provided by the 
eccentric weight 38 rotating in the die former 30. The top plate 44 is 
vibrated to assist in compacting the concrete and to remove air from 
within the wet concrete. A troweling or finishing plate 48 is positioned 
downstream of the top plate 44. This finishing plate 48 smooths out the 
top of the concrete slab 12 as the machine moves along the track 14 
leaving a smooth surface. An improved system for reciprocating the top 
plate 44 and a system for reciprocating side plates will be shown 
hereafter. 
The extruding machine described and shown in FIGS. 1 and 2 is the type 
known in the prior art. In both cases the vibrating mechanisms are powered 
by motors that have to rotate at about 12,000 rpm and these motors operate 
on a high frequency produced by a frequency converter 49 positioned on one 
end of the machine 11 as shown in FIG. 1. All frequency converters are 
excessively noisy which, added to the vibratory noise from the forming 
dies 30 and vibrating plate 44, provides an unpleasant work environment. 
FIGS. 3 to 5 illustrate an embodiment of the present invention with a 
different system for vibrating or eccentrically moving the die former 30. 
In this embodiment there is provided a compaction disc 50 mounted on the 
outlet end 27 of the extruder screw 26 and having a concentric disc face 
52 adjacent the outlet end 27 of the extruder screw 26 concentric with the 
extruder screw axis 53. The diameter of this concentric disc face 52 is 
somewhat smaller than the diameter of the outlet end 27 of the extruder 
screw 26 to ensure there are no restrictions to prevent the flow of 
concrete off the extruder screw 26. The compaction disc 50 has an 
eccentric disc face 54 which is not parallel to the concentric disc face 
52 but is coplanar with an input end 55 of the die former 56. The die 
former 56 at the input end 55 is mounted on a bearing 58 which in turn 
rotates on a bushing 60 which is eccentric to the conveyor screw axis 53. 
This eccentricity represents the same eccentricity as the compaction disc 
50 between the concentric disc face 52 and the eccentric disc face 54, and 
therefore the eccentric disc face 54 is coplanar and has exactly the same 
diameter as the input end 55 of the die former 56. 
The compaction disc 50 is keyed to a portion of the eccentric bushing 60 
concentric with the conveyor screw axis 53 and is attached to a tubular 
drive shaft 62 that rotates at approximately 500 rpm. Thus, the drive 
shaft 62 is rotated through gears or chain and sprocket by a motor driven 
off standard frequencies and no frequency converter is required. When the 
shaft 62 rotates, the compaction disc 50 rotates with it and the eccentric 
bushing 60 also rotates which causes the input end 55 of the die former 56 
to move in a circular orbital path about the extruder screw axis 53. The 
output end 63 of the die former 56 has another bearing 64 mounted on the 
end of the tubular drive shaft 62 concentric with the conveyor screw axis 
53. Thus the die former 56 may remain stationary as the tubular drive 
shaft 62 rotates. A Teflon, registered trade mark for 
Polytetrafluroethylene, seal 66 is provided in the input end 55 of the die 
former 56 which rotates up against the eccentric disc face 54 of the 
compaction disc 50. A further Teflon seal 67 is provided in the output end 
27 of the conveyor screw 26 which rotates up against the concentric disc 
face 52 of the compaction disc 50. These seals prevent liquid or concrete 
paste from entering the die former 56 or cavities in the conveyor screw 
26. 
FIG. 4 illustrates a section looking in the direction of arrows 4--4 in 
FIG. 3 on the eccentric disc face 54 showing that the eccentric disc face 
54 is not concentric with the conveyor screw axis 53. FIG. 5 illustrates 
the same section looking in the direction of arrows 5--5 on the input end 
55 of the die former 56, showing how the seal 66 and the periphery of the 
die former 56 are eccentric relative to the conveyor screw axis 53 yet 
concentric with the eccentric disc face 54 of the compaction disc 50. 
A flexible seal 70 is provided between the output end 63 of the die former 
56 and the attachment end 71 of the finishing tube 32. The flexible seal 
70 permits the input end 55 of the die former 56 to move in the circular 
orbital path. The seal 70 compresses and flexes as the orbital movement 
moves the output end 63 of the die former 56 relative to the attachment 
end 71 of the finishing tube 32. As shown the finishing tube 32 is 
attached to a central shaft 72 by a thrust bearing 74, thus the finishing 
tube 32 is held in position but is free to rotate. The finishing tube 32 
is joined at the attachment end 71 to the flexible seal 70 by bolts 76. 
Long bolts 77 join the flexible seal 70 to the output end 63 of the die 
former 56, thus the finishing tube 32 and the die former 56 cannot rotate 
relative to each other, but can rotate together. 
The embodiment shown illustrates a die former 56 and finishing tube 32 
which have a circular cross-section, as shown in FIGS. 5 and 5A, and on 
this basis the die former 56 and finishing tube 32 are free to rotate but 
are not driven. If, however, the cavity or hollow in the concrete slab is 
not circular but is oval, or another non-circular shape, then the thrust 
bearing 74 is omitted and the finishing tube 32 is keyed to the fixed 
shaft 72, as shown in FIGS. 3A, 3B and 5B, so that neither the finishing 
tube 32 nor the die former 56 can rotate. The die former 56 to produce a 
non-circular cavity starts with a circular input end 55 and slowly changes 
shape along the length to the required shape at the output end 63. This is 
seen in FIG. 3B which is a cross-sectional view looking downstream from 
the input end 55 of the die former 56 similar to FIG. 5 which shows a die 
former 56 to produce a circular cavity. The cross-sectional shape of the 
finishing tube 32, as shown in FIGS. 5A and 5B, is preferably slightly 
smaller than that of the output end 63 of the die former 56 to allow for 
relaxation of the concrete as it hardens. 
As well as compacting the concrete with the eccentric rotation of the die 
former 56, in another embodiment, compacting side plates 90 are provided 
as shown in FIGS. 7 and 8. Side members 92 of the extrusion machine 11 
support the compacting side plates 90 with flexible mountings 94, and 
rubber seals 96, at the bottom of the side plates 90 rest on the tracks 14 
to prevent concrete paste leaking as the extrusion machine 11 advances. 
As shown in FIG. 8, a drive shaft 98 is supported by two pillow block 
bearings 100 mounted on the side member 92, and is driven by a chain and 
sprocket 102. A motor which, is preferably a 3600 rpm motor (not shown), 
so that it can operate on a standard frequency rotates the shaft, and the 
drive shaft 98 has an eccentric end 104 which rotates in another pillow 
block bearing 106 mounted on the inside of the compacting side plate 90. 
Thus an eccentric movement from the eccentric shaft end 104 is transferred 
to the compacting side plates 90 which has a compacting effect upon the 
sides of the concrete slab 12 as the machine 11 advances. 
FIGS. 9 and 10 illustrate a compacting top plate 110 replacing the 
vibratory top plate 44 shown in FIG. 2. A cross support member 112 extends 
across the two side members 92 and has a bracket 114 attached thereto 
having a motor 116 which drives belt drive 118 to a drive shaft 120. This 
is supported on pillow block bearings 122 from the cross support member 
112. The drive shaft 120 has eccentric end bushings 124 which rotate in 
bearings 126 attached to a reciprocating arm 128 attached to the 
compacting top plate 110 by rubber bushings and washers 130. The motor 116 
rotates at 3600 rpm in one embodiment and provides a reciprocal movement 
through the eccentric bushing 124 and the rubber bushings 130 to the 
compacting top plate 110. The compacting effect is adequate for compacting 
the concrete and releasing air. A finishing plate 48 is shown supported 
from the cross support member 112 and performs the same function as shown 
in FIG. 2. 
FIG. 6 illustrates a concrete extruded slab 12 resting on a base 14 having 
cavities 80 therein. After the machine 10 as shown in FIG. 1 and FIG. 6A 
has extruded the slab 12, and the concrete has hardened, it is cut by a 
diamond saw into the required lengths. 
The extruder screw 26 generally rotates at about 50 rpm, whereas the 
compaction disc 50 is required to rotate at about 500 rpm. It has been 
found that a vibratory motor 46 mounted on a top plate 44 as shown in FIG. 
2 may rotate at approximately 3600 rpm. An eccentric weight rotating at 
this speed provides sufficient vibration to assist in compacting the 
concrete and releasing air as the concrete slab is formed. The top plate 
44 is supported on mounts (not shown) that are sufficiently flexible so 
the rotor 46 vibrates the plate 44. 
Various changes may be made to the embodiments shown herein without 
departing from the scope of the present invention which is limited only by 
the following claims.