Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to an extrusion machine fox
making elongated articles of concrete.
The extruding of concrete through a mold, usually
by the use of a screw conveyor to force the concrete through
S the mold, is well known. U.S. Patent 3,159,897 issued
December 8th, 1964 to Ellis discloses a machine having a
plurality of spiral conveyors or augers each with a flight
fixed to a core shaft. Each auger has a trowelling mandrel
secured to the downstream end and that mandrel rotates with
the auger. A vibrator is mounted on the machine outside the
molding area so that the entire machine is vlbrated. In the
Ellis machine the trowelling unit is fixed to an auger and
rotates with it and the machine thus forms concrete slabs in
which the cores must be of circular cross section.
Canadian Patent 910,030 issued September l9th,
1972 describes an extrusion machine having a forming element
of any cross sectional shape. In the extrusion machine of
Canadian Patent 910,030 there is a forming element of any
cross sectional shape independent of and ;mm~;ately follow-
ing the downstream end of the spiral conveyor. That forming
element is mounted so as not to be rotated by the conveyor.
It may be nonrotated or it may be rotated at a speed diffe-
rent from the conveyor or indeed at a speed the same as the
conveyor but the feature of the patent is that the spiral
conveyor and the forming element can be driven independently.
Canadian Patent 1,031,934 issued May 30th, 1978
shows a machine for extruding elongate articles of concrete
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in which a fixed transverse plate is positioned across the
upstream end of the mold and in which the conventional
screw conveyor is used to force the concrete towards the
mold. The invention of this patent is directed to formation
S o concrete bodies having cores of different sizes. In this
patent the molding elements do not rotate.
Canadian Patent 1,100,297 issued .~ay 5th, 1981
shows an extrusion machine of a generally similar ty~e but
including a support tube so that reinforcing members may be
introduced into the formed article. However, again tne
patent generally discloses a machine having a molding
section wlth a forming element in it and in which concrete
is forced through the mold by a screw conveyor.
The above machines generally move along a track on
wheels and extrude the formed concrete body on the upper
surface of the track. This is possible because the concrete
is a rPlatively stiff mix and, of course, modern technology
permits rapid setting of concrete.
The above machines have proved useful but, espe-
cially at present, it is important to seek ways in which them j n i mllm amount of concrete is used to produce a body of
adequate strength. In this regard all the prior art machines
could possibly be said to be inadequate because the structure
of the machines has not allowed the production o~ concrete
bodies in which the cores are above a certain percentage of
the cross sectional area. A relatively large core cross
section would in fact be perfectly acceptable in producing a
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body of adequate strength but the machines available are not
able to produce such bodies. It would fox example, be
desirable in certain circumstances, to produce bodies in
which the core is relatively deep, but in which the outer
walls provide sufficient material to meet the structural
requirements, but considerable problems have been encoun~
tered in attempting to produce such ~odies.
The present invention seeks to provide a machine
in which an optimum cross section of a hollow concrete body
can be produced, that is the minimum amount of concrete can
be used to produce a body of the required strength.
Accordingly, the present invention is an extrusion
machine for making elongated articlss of concrete by forcing
the concrete through a mold, the article having a relatively
large cavity and using the optimum amount of concrete for
required strength, the machine being moved forwardly by
reaction as the concrete is forced against the molded
concrete, a rotatable spixal conveyor in and ext~nd; ng
longitu~;n~lly of the mold for moving the concrete through
the mold; a nonrotatable forming element in tne mold to form
the internal cavity ;~e~iately following the downstream end
of the conveyor, the forming element having (a) its lower
edge positioned so that not more than 10% of the height of
the forming element is below the lower edge of the conveyor,
said lower edge and lower sides being free of any substan-
tial ramp, (b) its longitudinal center line higher than the
center line of the conveyor and (c) a ramp extending upwardly
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from the downstream end of the conveyor, the conveyor
forcing the concrete over the forming elements to form the
concrete article.
It is extremely desirable ~hat there be a vibrator
within the forming element. It is also useful, on occas-
ions r to include vibrator plate on top of tne mold, abo~e
the forming element.
The forming element should be free of any sub-
stantial ramp at its bottom upstream edge and sides. How-
ever, a ramp is permissible provided it is short. ~tslength must not exceed 25~ of the length of the forming
element.
As is common with machines as discussed in the
prior art it is desirable that there be a plurality of
forming elements. The first element is formed with a
vibrator and the subsequent elements are unvibrated. There
is thus a damper means between each formlng element.
Aspects of the invention are illustrated, merely
by way of example, in the drawings in which:
Figure 1 is a general view of a machine according
to the present invention;
Figure 2 is a section through a machine according
to the present invention;
Figure 3 is a section along the line 3-3 in Yigure
2; and
Figure 4 is a detail of the machine illustrated in
Figures 2 and 3.
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Figure 1 illustrates an extrusion machine 10
showing a block 12 extruded from the machine onto a base and
track 14. There is a hopper 16 through which the concreke
is fed to the machine 10 and an electric motor 18 to turn
the screw conveyors 20 and 22 shown in more detail in
Figures 2 and 3. The machine 10 has wheels 24 to move along
the upper surface of the track 14.
Figure 2 illustrates the machine in more detail.
Rotatable spiral convayors 20 and 22 extend longitudinally
of a mold 26. Concrete is fed through the hopper 16 and the
m~çh; ne 10 moves forward as the conveyors force concrete
against the already formed article. An internal cavity is
formed in the extruded article. In the illustrated embodi
ment the intarnal cavity has a depth, defined by its posi-
tion at formation, greater than its width but this is notessential. The invention, in effect, produces articles with
relatively large cores compared with the prior art. The
cores may be large by extending upwardly or laterally to an
extent not possible in prior art machines. This is achieved
in the present invention by the provision of forming elements
28, 30 and 32 each having its lower edge in line with a
lower edge of the conveyor as illustrated particularly in
Figure 2. However, it should be noted that the s~ne results
can be achieved if the forming element lower edge is below
the lower edge of the conveyor provide~ that not more than
10% of the total height of the forming element is below the
lower edge of the conveyor. The longitud;n~l center line A
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of the elements is higher than the center line B of tne
conveyor, as particularly illustrated in Figure 4, and a
ramp 34 as shown in Figures 2 and 4, extends u~wardly from
the downstream end of ~he conveyors 20 and 22 that i5
adjacent the end of the conveyor, within the mold 26.
The machine has, as may be considered conven-
tional, a main frame 36 having side members 38 and cross
members 40. ~here is a mounting frame 42 mounted on the
side members 38 which extends across the machine. This
mounting frame 42 can be adjusted up and down by the provi-
sion of bolts 44. The main frame 36 is provided with wheels
24 that ride on the rails 14 but it is also necessary to
prevent the downstream end of the machine from rising during
operation. ~heels 46 engage the undersurface of the sides
38 as shown in Figure 2 to prevent any possible lifting of
the machine. Weights added to the downstream end of the
machine can be used instead. There are shown two s~iral
conveyors 20 and 22 although the skilled man will know that
wide variation of that number is possible. Each is mounted
at one end in suitable bearings 48 carried by mounting frame
42. Each conveyors is made of a flight 50 securad to or
formed integrally with a hollow shaft 52. ~s particularly
shown in Figure 4 the hollow shaft 52 has a straight section
extending part of the length of the conveyor but the section
increases outwardly towards the downstream end. However, it
may be of uniform cross section.
Conveyor 20 is rotated in its bearing 48 by a
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chain and sprocket arrangement 54 driven by electric ~llotor
18 mounted on frame 42. The second conveyor 22 may be
provided with a separate electric motor but is desirably
driven by the same electric motor 18 through gears 56 and a
chain and sprocket arrangement 58 ensuring that the two
conveyors 20 and 22 rotate in opposite directions.
The forming elements 28, 30 and 32 are each
mounted on a shaft 60 extending through the hollow core
shaft 52. The first element 28, with ramp 34 is attached to
the end of the internal shaft. The rPm~;n;ng elements 30
and 32 are then bolted successively first to the ramped
element 28 by bolts 62 which also engage in dampers 64.
This is because the first element 28 is provided with a
vibrator 66, driven by Plectric motor 68 through internal
shaft 70. The vibrator, which is a simple eccentric, will
not be described here further as it is well known in the
art. It should also be noted that an additional vibrator 72
may be provided on top of the machine as shown in Figure 2.
The structure of this vibrator 72 will also not be described
as it is conventional.
Again as is conventional the width of the body 12
to be produced may be controlled by side plates 74 mounted
on opposite sides of the mold 26. The side plates 74 are
mounted for adjustment on frame members 38 by bolts 76.
Similarly the depth of the mold 26 can be controlled by an
upper plate 78 positioned on top of the moldiny section and
adjustable on bolts 80 in conventional manner.
As previously indicated the position of tne
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forming elements in the mold can be controlled by bolts 44.
In operation concrete is fed through the hopper 16
to the spiral conveyors 20 and 22. The concrete is forced
over the forming elements 28, 30 and 32 in the mold 26 by
the screw conveyor. The machine is moved forward by the
reaction of the still fluid concrete against the formed
surfaces within the mold element and the machine then moves
on wheels 24 and deposits the formed elements 12 as shown in
Figure 1. Because of the concrete used the product sets up
extremely quickly and is self-supporting virtually ;mm~di ately
upon formation. The vibrator 66 in the first forming
element 28 ensures that the concrete flows smoothly around
the forming elements.
The particular virtue of the present invention is
that articles having relatively large cores and, for example,
cores that are of substantial depth relative to the deptn of
the article can be produced. This is made possible by the
having the center line B of the screw lower than the center
line A of the mold, by the provision of the ramp 34 on the
top of the first forming element 28 and by the absence of
any substantial ramp on the underside of the forming element.
It is also desirable that there not be a ramp on the lower
corners or sides of the forming element below the longi~u-
dinal axis of the screw as shown in Figure 4. ~owever, a
small ramp is permitted here provided that it is not of
great length or depth and does not exceed 25% of the forming
element length.
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The present invention thus permits the economical
production of concrete bodies having the same strength as
bodies produced on prior art machines but using less con-
crete.
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