Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relate~ to a method and
apparatus for forming continuous concrete structures, and in
particular a method and apparatus for continuously forming a
concrete curb.
Various apparatus are k:nown in the art for forming
continuous concrete curbs. In general, an open-ended curb
mold is used to define the cross-sectional shape o~ the curb.
The interior surfaces of the curb mold are adapted to ensure
that the concrete curb formed therein has an acceptable
surface finish when it leaves the open end of the mold. This
eliminates the necessity for finishing the curb by hand, after
it has been formed by the mold. A hopper generally encloses
the front end of the curb mold, and directs concrete into tha
curb mold. The hopper may also comprise vibrators, or other
means for compacting the concrete in the mold, and for
removing entrained air. This stiffens the plastic (i.e.
uncured) concrete so that it will retain the shape of the
curb mold, after the concrete has passed out of the open end
of the curb mold, until the concrete has cured.
The curb mold may be mounted on a machine adapted
for this purpose, such as, for example a Gomaco GT3300. This
machine comprises means for moving the mold at a controlled
speed along the dPsired path of the finished curb~ Typically,
a sensor system, for example a grade wire and probe, is used
to vary the vertical position of the curb mold with respect
to the ground, so as to ensure that the curb follows a
predefined grade.
By this means, it is generally possible to
economically construct any desired length of continuous
concrete curb, with a finished desired grade, and an
acceptable surface finish.
Typically, curb molds are constructed so that a
variety of cross-sectional shapes may be formed. One curb
mold is constructed for each different shape. one of the
most common shapes is a simple rectangular, or wall-like curb.
Another common curb shape includes a built~in gutter. The
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gutter curb is a variation of the simple rectangular curb.
In this case, a low step-like rectangular section is formed
integral with the base of the curb, on the side of the curb
facing the roadway. The top of the gutter portion of the curb
is maintained at or slightly below the finished road surface
elevation, typically using automat:ic control means such as the
above-mentioned grade wire and probe.
The conventional curb molds, as described above,
have proven to be an efficient means of forming concrete
curbs. However, their design is optimised to produce concrete
curb with a constant cross-section shape. When the mold is
used to build a curb past a lane-way, for example, the formed
curb must be modified by lowering the top of the curb down to
approximately the level o~ the finished road surface. In the
case of a simple rectangular curb, this can be accomplished
simply by lowering the curb mold by the required amount.
However, If the curb is constructed with a built-in gutter,
this approach is not possible, because the gutter must remain
at the level of the finished road surface.
A variety of solutions to this problem have been
proposed. The simplest is to form the curb using the curb
mold in the normal manner, and then manually cut away the
excess concrete as required ti.e. in the vicinity of the lane-
way). The surface of the reshaped curb is then refinished
by hand to achieve an acceptable surface finish. This
solution is labour-intensive, slow, and tends to produce a
significant amount of waste, particularly in areas
characterised by many lane-ways, such as housing developments.
In order to reduce the amount of labour and waste
concrete, it has been proposed to modify the curb mold by
adding a substantially vertical baffle which may be inserted
into the mold so as to block off the upper portion of the
mold. By this means, the upper portion of the curb may be
selectively "cut-off" in the vicinity of a lane-way. While
this method reduces the amount of wasted concrete, the
resulting curb must be finished by hand in order to achieve
an acceptable surface finish.
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It is th~refore an object of the present invention
to provide an apparatus for forming continuous concrete curb,
wherein the apparatus is adapted so that the top of the
finished curb can be varied, independently of the gutter or
lower portion of the curb, during the forming process.
According to one aspect of the invention, there is
provided an apparatus for forming continuous concrete curbs,
which apparatus comprises: an open ended mold section defining
the largest cross-sectional shaple of the finished curb; a
hopper generally enclosing the front end of said mold section
for directing the flow of plastic concrete into the mold; and
height adjusting means adapted for controllably adjusting the
height of the finished curb with respect to the lower portion
of said curb.
According to another aspect of the invention, there
is provided a curb forming machine for forming continuous
concrete curbs, which machine comprises: an open ended mold
section defining the largest cross-sectional shape of the
finished curb; a hopper generally enclosing the front end of
said mold section for dirscting the flow of plastic concrete
into the mold; and height adjusting means adapted for
controllably adjusting the height of the finished curb with
respect to the lower portion of said curb, wherein said height
adjusting means comprises: a top plate for shaping the top
surface of the curb; positioning means ~or adjusting the
vertical position of said top plate with respect to said mold
section; and control means for controlling said positioning
means.
The mold section may be formed to produce any
desired cross-sectional shape of the finished curb, within the
limitations of thP workability of the concrete being used.
For example, a curb with a built-in gutter portion. The mold
section defines tha largest shape o~ the curb, which may be
used, for example, away from any lane-ways etc.
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The hopper may comprise vibrators or other means for
compacting the concrete into the mold so as to stiffen the
concrete beEore it leaves the open end of the mold.
The height adjusting means generally comprises a
mold top plate, which is adapted to shape the top surface of
the finished concrete curb; a baffle attached to the forward
edge of the mold surface, to block off the portion of the mold
above the top plate and thus prevent concrete from passing
around the top plate; guide means for smoothly guiding the top
plate and baffle as they are alternately extended into and
withdrawn from, the mold section; and means for extending and
withdrawing the top plate and the baffle into (and out of) the
mold section so as to effectively lower and raise the top of
the mold with respect to the lower or gutter portions of the
finished curb. The top plate is further adapted to ensure
that an acceptable surface finish of the curb is obtained
irrespective of the vertical position o~ the top plate.
The height adjusting means may be either manually
of automatically controlled. For example, automatic control
may be effected by use of a grade wire and probe. In this
case, a first grade wire and probe may be used to control the
elevation of the cur~ mold as a whole. Thus the gutter
portion is maintained at the height of the finished road
surface. A ~econd grade wire and probe is then used to
control the elevation of the upper surface of the finished
curb, independently of the gutter portion~
The curb mold according to the invention may be
carried by an essentially conventional curb forming machine,
which has been suitably adapted for this purpose. As will be
explained in greater detail, the required modifications, even
for automatic control, are relatively simple and employ
readily available equipment. The invention can therefore be
implement~d as a comparatively inexpensive retrofit for
existing curb forming machines and molds.
According to another aspect the invention there is
provided a method of continuously forming a concrete curb,
which method comprises the steps of: maintaining a cu~b mold
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at a predetermined elevation with respect to the finished
grade of an adjacent road surface; supplying plastic concrete
to said mold, and compacting it therein 50 as to form the
curb; and controllably varying the vertical position of an
upper portion of said curb mo:Ld, with respect to said
predetermined elevation, so as to selectively vary the height
of said curb.
The preferred embodiments of the invention are
lo described, with reference to the appended drawings, in which:
Figure 1 is a perspective view of a conventional
curb mold o~ the built-in gutter type, and a section of curb
formed thereby;
Figure 2 is a perspective view of a curb mold of
the built-in gutter type according to the invention, and a
section of curb formed thereby;
Figure 3 is another perspective view of the curb
mold illustrated in Figure 2, and a section of curb formed
thereby; and
Figure 4 illustrates the use of two grade wires as
employed by the invention;
It will be noted that the above noted figures, and
the embodiments described herein refer to curbs of the built-
in gutter type. However, it will be understood that this is
by way of example only, and is not limitative o~ the
invention. It will be further noted that throughout the
figures, like features are referenced by like numerals.
Referring now ko Figure l~ A conventional curb mold
2 generally comprises a mold section 4l and a hopper 6 into
which plastic (uncured) concrete is placed. VibratGrs or
other compacting means (not shown) are employed to compact
the concrete into the mold section 4. As the curb mold
advances forward, the formed curb 3 emerges from the open rear
of the mold section 4. The vibrators or other compacting
means ensure that the plastic concrete has sufficient
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stiffness to resist slumping of the curb 3 before the concrete
has set and cured. The curb mold 2 is carri~d in close
proximity to the ground by a conventional curb molding machine
(not shown~ which maintains the curb mold 2 at a predetermined
elevation. For example, the curb molding machine typically
employs hydraulic actuators, controlled by a grade wire and
probe, to automatically adjust the height of the mold so that
the elevation of the gutter portion 5 approximately
corresponds with the finished height of the road ~urface. It
will be understood that the use of a grade wire and probe, in
this application, is well understood by those skilled in the
art, and therefore further detailed illustration and/or
description thereof is unnecessary.
It can be seen from Figure 1 that the mold section
4 is of a fixed geometry. Thus the height of the curb 3 is
determined by the shape of the mold section 4, and the
requirement that the gutter elevation conform to the roadway.
Thus in particular areas, or example in the vicinity of a
lane-way, at least a portion of the formed curb 3 must be cut
away, and the surface refinished, in order to lower to top of
the curb 3 by the required amount to permit passage of
vehicles or the like.
Figures 2 and 3 illustrate a curb mold accordiny
to the present invention. Like the conventional curb mold
illustrated in Figure 1, the curb mold of the invention is
carried in close proximity to the ground by a curb molding
machine ~not shown). The curb molding machine of the
invention is essentially a conventional curb molding machine
which has been adapted to permit either manual or automatic
control of the height adjusting means, and will be described
in more detail later.
~ curb mold according to the invention comprises a
mold section 4, a hopper 6 and a height adjusting means,
referred to ganerally by reference numeral 8. The height
adjusting means 8 comprises a movable top plate 10, which is
shaped to conform to the upper surface of the mold section
4. By this means, when the top plate 10 i~ in its fully
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raised position (as seen in Figure 2), it forms a surface
contiguous with the upper surface of the mold section 4. In
this condition, the curb mold produces a curb 3 of a maximum
height, in precisely the same manner as the conventional curb
mold illustrated in Figure 1. Disposed at front end (i.e.
towards the hopper 6) of the top plate 10 is a baffle plate
12. Similarly, a keeper plate 13 is disposed at the rear of
the top plate 10.
When the top plate lO is extended downwards into the
upper portion of the mold section 4, the contour of the top
plate 10 ensures that the upper surface of the formed curb
retains an acceptable profile and surface finish. The baf~le
plate 12 effectively closes off the portion of the mold
section 4 that extends above the level of the top plate 10.
By this means, the use of concrete varies with the size of the
cross-section of the curb being formed, and waste is reduced
to a minimum. In addition, the baffle plate 12 and the keeper
plate 13 are adapted to operatively slide in guides 14
provided on the outside of the mold for this purpose. Thus
the baffle plate 12 and the keeper plate 13 act to maintain
the top plate 10 in a correct alignment with respect to the
mold section 4, and prevent the top plate 10 from being forced
out of position by the pressure of the concrete in the hopper
6 and mold section 4. To further prevent displacement of the
top surface 10 during operation, gusset plates or other
bracing means (not shown) may be employed.
The vsrtical position of the top plate 10 is
controlled by positioning means 16 (for example, a hydraulic
actuator as illustrated in Figures 2 and 3) mounted between
the top plate 10 and a suitable mounting fram (not shown)~
As can be se~n in Figure 2, when the top plate 10
is raised to its maximum height, the curb mold according to
the invention functions in the same manner as the conventional
curb mold. Howevex, when the positioning means 16 extends
the top plate 10 downwards into the mold, as illustrated in
Figure 3, the top plate 10 and baffle plate 12 cooperate so
as to effectively reduce the height of the top of the curb 3
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relative to the gutter portion 5. Thus by selectively
lowering and raising the top plate 10, the finished height of
the curb 3 can be varied as required, for example in the
vicinity of lane-ways. Furthermore, the contour of the top
plate 10 ensures that the formed curb 3 will have an
acceptable surface finish, regardless of the height of the
curb 3, without the need Eor manual refinishing.
As mentioned previously, the vertical position of
tha top plate 10 is adjusted by positioning means 16, such
as a hydraulic cylinder, operatively mounted on a suitable
support frame (not shown). When the curb mold of the
invention is installed on a curb forming machine, means
provided thereon may be used to either manually or
automatically control the positioning means 16.
In the case of manual control, two methods may be
employed.
The conventional curb forming machine, such as a
Gomaco GT3300, comprises manually and/or automatically
controlled hydraulic circuits to ad~ust such parameters as the
height of the machine, the attitude (i.e. ~o keep the machine
level), and the lateral (i.e. side-to-side) offset of the
machine. Additional hydraulic circuits are used to propel the
machine in forward and reverse directions, as well as to
effect directional control.
Prior to starting to form a curb, the curb mold is
attached to the curb forming machine, which is then moved into
a position so that the curb mold is in close proximity to the
starting point for the curb, and aligned parallel to the
desired curb path. The curb mold is then levelled by
levelling the curb forming machine, and adjusted laterally~
using the lateral offset controls of the curb forming machine,
so that it is located vertically over the correct position for
starting the curb. Finally, th~ curb mold is lowered to the
correct elevation by lowering the curb forming machine until
a sensor probe attached thereto engages a grade wire which has
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been previously set out along the path of the curb. The grade
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wire is supported on poles or stakes placed at intervals
beside the desired path of the curb, and is set such that it
accurately defines the elevation of the curb. As the curb
forming machine forms the curb, the vertical height of the
curb forming machine (and therefore the curb mold) is
continuously adjusted in response to control inputs generated
by the sensor probe and the grade wire, so ~hat the elevation
of the finished curb conforms to the profile defined by the
grade wire.
In practice, it has been found that the lateral
offset circuit of the curb forming machine is used only during
the initial set-up prior ko starting the curb forming run.
Thereafter, the lateral adjustment of the curb is performed
by effecting steering corrections to the direction of travel
of the machine.
Thus in a first embodiment of the invention, the
positioning means 16 may be manually controlled using the
~! ~; t I lateral offset hydraulic circuit. In this case, the curb mold
and curb forming machine are set up and adjusted, prior to
2U beginning a curb forming run, in the usual manner. However,
immediately prior to starting the run, the hydraulic lines of
the lateral offset circuit are disconnected from the lateral
offset hydraulic actuator, and connected instead to the
positioning means 16. The conventional hydraulic lines and
couplers, whic~`-are already installed on the conventional
curb forming machine are ideal for this purpose. The
conventional couplers include a valve means which
substantially prevents leakage of significant q~lantities o~
hydraulic fluid. Thus when the hydraulic lines are
disconnected from the lateral offset hydraulic actuator, the
actuator is effectively locked in position. Under these
conditions, the curb forming operation may proceed in the
conventional manner until ~uch times as the curb forming
machine arrives at a location, such as near a lane-way, where
the top of the curb 3 must be lowered. At this point in the
operation, the operator of the curb forming machine uses the
manual control for the lateral offset to extend the
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positioning means 16, thereby lowering the top plate 10 into
the mold section 4 and effecting the required lowerlng of the
top of the curb 3. Similarly, the operator can raise the top
of the curb 3 by retracting the positioning means 16, again
using the lateral o~fset controls of the curb ~orming machine.
In a second embodiment of the invention, which also
employs manual control ~or adjusting the positioning means 16,
a separate hydraulic circuit is added to the conventional curb
¦ forming machine. This eliminates the need for disconnecting
the lateral offset hydraulic circuit of the curb forming
machine. In addition, a separate curb height adjustment
circuit can be designed to provide the operator with a greater
degree of control than is possible by using the lateral offset
circuit and controls.
A third embodiment of the invention permits the
height of the curb to be automatically controlled. It will
be recalled that during a conventional curb forming operation,
the vertical position of the curb mold is continuously
adjusted by using a sensor probe and grade wire to control the
vertical adjustment hydraulic circuit of the curb forming
machine. Automatic control of the positioning means 16 may
be performed in an analogous manner.
In this case, the sensor probe may be disposed on
mounting means depending from the height adjusting means 8.
In this manner, the sensor probe moves vertically in direct
relation to the top plate 10. A curb height grade wire, in
addition to the grade wire described above, is used in
conjunction with this second probe to supply control input
signals to an automatic hydraulic circuit in a manner directly
analogous to that used to adjust the vertical position of the
curb forming machine itself. As may be seen ~rom Figure 4,
in this embodiment, two grade wires are mounted on support
posts 20 set out beside the desired path of the curb 26, which
may be at least partially graded and prepared. A first grade
wire 22 defines the elevation profile of the curb mold as a
whole. Thus grade wire 22 is used to maintain the elevation
of the gutter at a predetermined height with respect to the
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ll
finished surface of the roadway. A second grade wire 24 is
then used to define the profile of the top of the curb, ~or
example, as shown in Figure 4, defining a smooth transition
between a general curb section and a lane-way.
It will be apparent to those skilled in the art that
there are various ways in which the invention may be modified.
For example, the positioning means 16 could electrical instead
of hydraulic. In this case, an electric motor and a drive
screw might be used in conjunction with appropriate control
means to effect the desired positioning of the top plate 10.
In another alternative~ the positioning means 16
might comprise more than one actuator. For example, two
actuators, disposed at opposite ends of the top plate 10 could
be employed. By this means the two actuators could be
independently controlled (for example by using two probes
travelling along the grade wire 24) so that the slope of the
top plate 10 may be adjusted to more accurately follow the
contour of the top of the curb 3, and thereby improve the
surface finish, during height transitions.
~ urthermore, it will be seen that in the appended
figures, the height adjusting means 8 comprises only a portion
of the top of the mold section 4. However, it will be obvious
that the height adjusting means 8 could be extended such that
the top of the mold section 4 is almost entirely composed of
the top platP 10.
