Note: Descriptions are shown in the official language in which they were submitted.
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CONCRETE WALL BLOCK
Field of the Invention
The invention relates to concrete blocks, such as wet cast or dry cast
concrete
blocks for use in the creation of walls, including blocks having an embossed
front face.
More particularly, the invention relates to concrete blocks with natural stone
appearance
for use in the creation of curved walls, such as retaining walls.
Background Art
Concrete blocks are well known for the use in landscaping applications,
particularly retaining walls. Various different block configurations or shapes
are known.
To allow the assembly of curved walls, concrete retaining wall blocks are
usually provided
with a rearwardly tapered body with sidewalls that are at an angle of less
than 90 degrees
to the front face of the block. Stacking such blocks side by side with the
angled sidewalls
of adjacent blocks engaging one another results in a convexly curved wall.
Concave
curvatures are obtained by stacking the blocks side by side with the front
edges touching,
while the tapered rear ends are spaced apart. This provides significant
flexibility in the
creation of curved walls the radius of curvature of the wall being limited
solely by the
angle of the sidewalls relative to the front face. However, tapered blocks and
walls built
with such blocks have several drawbacks.
Straight walls built with stacked blocks of tapered shape have a substantially
continuous front face, but include a pattern of multiple gaps in the back face
of the wall,
due to the angled sidewalls. In fact, even curved walls with a curvature less
than the
maximum convex curvature allowed by the taper of the blocks will always
include this
pattern of gaps. Consequently, tapered blocks cannot be used to build
freestanding walls,
since the appearance of the rear wall will be very different from the front
face and will not
be aesthetically pleasing due to the pattern of gaps. A freestanding wall with
natural
appearance on both sides is not achievable with tapered blocks. Thus, a wall
block system
for building freestanding curved walls is desired, wherein all sides are
continuous and
have a natural stone appearance.
The retaining capacity of a retaining wall is determined in part by the mass
of the
wall. However, the gaps formed in the rear surface of walls made with tapered
blocks
significantly reduce the overall mass of the wall. Thus, a wall blocks system
for
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freestanding curved walls is desired, which maximizes the mass of the wall and
minimizes
any gaps between laterally adjacent wall blocks.
Molding dry cast tapered blocks with converging side walls and an embossed
front
face is challenging due to the need for stripping the compressed block from
the mold. Dry
casting uses a no slope concrete mixture which is filled into a mold cavity
and compressed
to sufficiently pre-consolidate the block to permit handling of the block
prior to curing of
the concrete mixture. After pre-consolidation, the block is stripped from the
mold and
transported to a curing station for curing of the concrete mixture. Stripping
of the block is
achieved by pushing it out of the mold with a stripper shoe which has a dual
function. The
stripper shoe is used during pre-consolidation to compress the dry cast
concrete mixture.
After pre-consolidation, the stripper shoe is used for forcing the pre-
consolidated block
from the mold. To produce blocks with an embossed surface structure or pattern
on the
front face, the stripper shoe is provided on its dry cast mixture engaging
face with a
negative of the three-dimensional surface structure to be produced on the
block face
during pre-consolidation.
Stripping the pre-consolidated block by pushing it from the mold requires a
clear
path for the block through the mold, which mandates the use of movable mold
walls in the
manufacture of tapered, embossed blocks. To facilitate handling and stacking
of pre-
consolidated embossed blocks and especially to minimize damage to the embossed
front
face during curing, the embossed blocks are usually manufactured with the
front and rear
faces oriented up and down in the mold, respectively. That means the sidewalls
of the
mold must be movable from the angled position required for the shaping of the
tapered
shape of the block, in order to provide a clear path of the block through the
mold. Thus,
embossed wall blocks for the assembly of curved walls are desired which are
more easily
manufactured.
It is now an object of the invention to overcome at least one of the
disadvantages
associated with known dry cast embossed wall blocks.
Summary of the Invention
In a preferred embodiment, the invention provides a stackable concrete wall
block,
having a prism shaped body with front and rear faces, in a stacked
orientation, top and
bottom faces for placement opposite like blocks positioned above and below in
a stacked
condition of the wall block and at least a pair of side walls for placement
opposite a like
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block placed side by side to the wall block, and a lip protruding from at
least one of the
sidewalls and coplanar with the front face for spacing the body of the block
from the body
of a like block placed adjacent thereto. Preferably, the front face of the
block and the lip
have a three-dimensional surface structure, preferably an embossed surface
structure. The
block is preferably a dry cast, embossed concrete block.
The lip is preferably provided on one or both of the side walls to create
lateral
spacing between concrete blocks stacked side by side in a wall, while
providing the wall
with a continuous front face. As is the case with tapered blocks, this spacing
allows the
assembly of curved walls. However, a prism shaped block with straight side
walls and a
lip is more easily manufactured than a tapered block with angled side walls,
since no
movable mold walls are required, when the block is a dry cast block. The lip
can be
achieved by way of a draw plate which is placed in the mold for filling and
compression of
the dry cast mixture and is pulled from the mold cavity prior to stripping.
The use of draw
plates in the manufacture of dry cast concrete blocks is known, but is
generally used for
the production of three-dimensional structures and/or undercuts on the rear
face of the
block.
The lip preferably has a depth which is at the maximum 50% of the overall
depth
of the block as measured from the front face to the back face and preferably
between 5%
and 50%, most preferably between 25% and 50%.
In another preferred embodiment, the dry cast concrete block further includes
a
connecting structure for connection of a secondary structure, such as a
setback pin, a like
concrete block, a veneer block, or a filler block to the rear face of the
concrete block.
Filler blocks are used for covering any rearward gap created in an installed
condition by
the lip between the block and an adjacent like block. A back to back
attachment of a pair
of like blocks by way of the connecting structure allows for the assembly of a
two sided
wall. The connecting structure is preferably a dovetail type connection with
one or more
female connector members provided in a back surface of the wall block and a
corresponding number of complementary male connector members provided on the
secondary structure to be connected to the back surface.
In a further embodiment, the invention provides a set of dry cast concrete
blocks
including a wall block, a filler block and a connecting structure for
connecting the wall
and filler blocks in a back-to-back arrangement. The wall block preferably has
a prism
shaped body with front and rear faces, in a stacked orientation, top and
bottom faces for
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placement opposite like blocks positioned above and below in a stacked
condition of the
wall block and at least a pair of side walls for placement opposite a like
block placed side
by side to the wall block, and a lip protruding from at least one of the
sidewalls and
coplanar with the front face for spacing the body of the block from the body
of a like
block placed adjacent thereto. Preferably, the front face of the block and the
lip have a
three-dimensional surface structure, and the filler block has a prism shaped
body with
generally front, rear, top and bottom faces and generally parallel side walls.
In a preferred embodiment of the set of concrete blocks, the wall block has an
overall width X, n protruding lips, with n=1 or 2 and each lip having a
protruding width Y,
the wall and filler blocks have the same depth and the overall width of the
filler block is
between X and X-2nY. The wall and filler blocks may have a different height.
In another preferred embodiment of the set of concrete blocks, the wall block
has
an overall width X, n protruding lips, with n=1 or 2 and each lip has a
protruding width Y
and a depth B. The wall block has a depth A and the filler block has a depth C
and the
overall width of the filler block is between X and X-n(Y+YC/A-B). The wall and
filler
blocks may have a different height.
The connecting structure is preferably in the form of a dovetail type
connection
with one or more male connector members provided on one of the wall and filler
blocks
and a corresponding number of female connector members provided on the other
of the
wall and filler block. Alternatively, the connecting structure may be a
separate connector
insertable into complementary recesses in the wall and filler blocks. However,
any other
connecting structure can be used, which is incorporated into or separate from
one or both
of the wall and filler blocks, as long as the connecting structure renders the
wall and filler
blocks connectable in a back-to-back orientation.
Brief Description of the Drawings
The invention will now be further described by way of exemplary embodiments
and with reference to the attached drawings, wherein,
Fig. 1 is a perspective view of a pair of wall blocks spaced apart by the lip
portion;
Fig. 2 is a perspective view of a pair of wall blocks as shown in Fig. 1, but
positioned to touch at the lip and at the rear edge, to form an angled
arrangement;
Fig. 3 is a perspective view of a wall block and a filler block in separation
and
when engaged;
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Fig. 4 is a perspective view of a wall and filler block combination as shown
in Fig.
3, with the filler block having the same length as the wall block;
Fig. 5 is a schematic illustration of a curved wall assembled with the set of
wall
and filler blocks of Fig. 3;
Fig. 6 is a schematic illustration of a curved wall assembled with a the set
of wall
and filler blocks similar in construction as the set of Fig. 3, but with the
blocks being
longer;
Fig. 7 is a schematic illustration of a curved wall assembled with the
different sets
of wall and filler blocks of Figs. 6 and 7;
Fig. 8 is a schematic illustration of a straight wall assembled with the set
of wall
and filler blocks of Fig. 4;
Figs. 9a to 9c are perspective, front elevation and top plan views of a mold
frame
arrangement for the dry casting of a set of short and long wall and filler
blocks;
Figs. 10a to 10d are perspective, bottom plan, front plan and end elevation
views of
a wall block with a stepped lip;
Fig. 11 is a schematic illustration of a curved wall assembled with the wall
blocks
of Figs. 10a to 10d;
Figs. 12a and 12b are a front and top perspective view and a front plan view
of a
partial wall including seven (7) stacked blocks in accordance with one aspect
of the
invention; and
Fig. 13 is atop plan view of the first row of blocks of the partial wall shown
in
Figs. 12a and 12b.
Detailed Description
The present application is directed to a wall block for use in retaining walls
or
freestanding walls, preferably a cast concrete block, more preferably a dry
cast, embossed
concrete block.
In a preferred embodiment as illustrated in Figs. 1 and 2, the wall block 100
includes, a prism shaped body 110 with a front face 112, a rear face 114, top
and bottom
faces 116 and 118 and generally parallel side walls 119. The wall block 100
further
includes a protruding lip 120 on at least one of the side walls 119, which lip
120 protrudes
from the side wall 119 and is coplanar with the front face 112. The lip 120
can be provided
on either one or both of the side walls 119. The spacing created by the lips
120 allows the
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assembly of straight walls as shown in Fig. 1 or curved walls as shown in Fig.
2, by
arranging the wall blocks in such a way that terminal edges of the block at
the lip 120 and
the rear face 114 touch the respective edges of an adjacent wall block. The
protruding
length of the lips 120 determines the radius of curvature which can be
achieved by
placement of the wall blocks 100 side by side in wall with the lips 120 and
the bodies 110
of adjacent blocks touching (see Figs. 5-7). The larger the protruding width
of the lips, the
smaller the minimum radius achievable. Moreover, the shorter the length of the
wall block
100, the smaller the minimum radius achievable.
In the installed condition of the wall block 100, wherein the wall block 100
is
stacked with like wall blocks 100 into a wall, the lip 120 provides for
spacing between the
bodies 110 of adjacent wall blocks 100 placed side by side, while providing
the resulting
wall with a continuous front surface, as shown in Fig. 1. The front face 112
of the block,
which extends over the lip 120, preferably has an embossed three-dimensional
surface
structure. Preferably the front face 112 is embossed with a surface structure,
which
provides the wall block 100 and any wall assembled with such wall blocks with
the
appearance of natural stone. This feature will be described in more detail
further below
with reference to Figs. 10-13.
The lip 120 can be provided on either one or both of the side walls 119,
preferably
both, to create bi-lateral spacing between the bodies 110 of wall blocks 100
stacked side
by side in a straight wall (see Fig. 1), while providing the wall with a
continuous front
surface. As is the case with tapered blocks, this spacing allows the assembly
of curved
walls, by arranging the wall blocks in such a way that terminal edges of the
front and rear
faces 112, 114 of adjacent wall blocks 100 are in engagement (see Fig. 2).
A wall block 100 with a prism shaped body 110 with parallel side walls 119 is
more easily manufactured by dry casting than known, tapered blocks, since no
movable
mold walls are required.
In another preferred embodiment as illustrated in the Figures, the dry cast
wall
block 100 further includes a connecting structure 300 for connection of a
secondary
structure to the rear face 114 of the wall block 100. The secondary structure
can be a
setback pin, a like block, a different block, or a veneer. The different block
is preferably a
filler block 200 as shown in Figs. 3 and 4 for covering any rearward gap
created in an
installed condition by the lip between the block and an adjacent like block.
The connecting
structure 300 includes at least one pair of interconnecting protruding and
recessed
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elements, most preferably in the shape of a dovetail arrangement (see Figs. 3-
8), one of the
elements being incorporated into the rear face 114 of the wall block 100 and
the other one
into the secondary structure. The connecting structure preferably includes
multiple
alternating protruding and recessed elements 310, 320 in the shape of a
repeated dovetail
arrangement as shown in Figs. 3 and 4. The filler block 200 is provided for
covering any
rearward gap created by the lip 120 between the wall block 100 and an adjacent
like block
100 in the installed condition. When the wall blocks are installed in a curved
configuration, the length of the filler block must be less than the length of
the wall block
(see Figs. 3 and 5-7), while in a straight configuration the filler block must
have the same
length as the wall block (see Figs. 4 and 8).
A preferred embodiment of a filler block 200 is illustrated at different
lengths in
Figs. 3 and 4. The filler block 200 includes a prism shaped body 210 with a
front face
212, a rear face 214, top and bottom faces 216 and 218 and generally parallel
side walls
219. The filler block 200 further includes a connecting structure 330 which
interlocks with
the connecting structure 300 on the wall block 100 for connection of the
filler block to the
rear face 114 of the wall block 100. The connecting structures 300 and 330 are
preferably
of complementary shape in order to provide for an interlocking of the wall and
filler
blocks 100, 200.
In a further embodiment (as illustrated in the bottom portion of Figs. 3 and
4, there
is provided a set of dry cast concrete blocks including a wall block 100 and a
filler block
200. The wall block 100 has a prism shaped body 110 with an embossed front
face 112
and generally planar rear, top and bottom faces 114, 116, 118 and generally
parallel side
walls 119, and a protruding lip 120 extending from at least one of the
sidewalls and
coplanar with the front face 112 for spacing the body 110 of the wall block
100 from the
body of a like block placed adjacent thereto, while providing a continuous
front surface.
The front face 112 of the wall block 100 and the lip 120 have a three-
dimensional surface
structure embossed into the front surface by the stripper shoe in the dry cast
molding
process. The three dimensional structure preferably provides the wall block
with a front
face 112 having the appearance of natural stone. The filler block 200 has a
body 210
shaped as a rectangular prism and having a front face 212, a rear face 214,
top and bottom
faces 216, 218 and generally parallel side walls 219. The filler block 200
preferably has a
three-dimensional surface structure embossed into the front surface 212 by the
stripper
shoe in the dry cast molding process. The three dimensional structure
preferably provides
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the filler block 200 with a front face 212 having the appearance of natural
stone. The wall
block 100 further includes a connecting structure 300 and the filler block 200
of the set of
blocks includes a connecting structure 330 for connecting the wall and filler
blocks in a
back-to-back arrangement.
A pair of interconnected wall and filler blocks 100, 200 is illustrated in
each of
Figs. 3 and 4. In each pair, the interconnecting structure 300 and 330 is a
series of dovetail
shaped protrusions 310, 340 alternating with dovetail shaped recesses 320, 350
in the
respective rear faces 114 and 214 of the wall and filler blocks 100, 200. The
dovetail
shaped connectors on the respective rear faces are offset so that the a
protrusion 310 in the
rear face 114 of the wall block 100 engages a recess 350 in the rear face 214
of the filler
block 200 and a connector 340 in the rear face 214 of the filler block 200
engages a recess
320 in the rear face 114 in the wall block 100.
The protruding length Y of the lips 120 determines the radius of curvature
which
can be achieved by placement of the wall blocks 100 side by side in a wall
with the lips
120 and the bodies 110 of adjacent blocks 100 being in engagement. The larger
the
protruding width Y, the smaller the minimum radius achievable. An angle a is
enclosed by
the side wall 119 of the wall block 100 and an imaginary line 400 connecting
the free end
121 of the protruding lip 120 with the terminal edge 115 of the rear wall 114.
This angle is
the minimum angle at which adjacent wall blocks can be placed without forming
a gap
between the blocks at the front face 112. Of course, wall blocks 100 can also
be placed
side by side in straight alignment to form a straight wall, in which case the
protruding lips
120 are in engagement, but the blocks do not touch at the rear face 114,
resulting in a
space between adjacent wall blocks 100 at the rear face 114. In order to
provide the
straight wall with continuous front and rear surfaces, filler blocks 200 are
used which have
the same overall width X as the wall blocks 100, as shown in Figs. 4 and 8. To
achieve a
curved wall, the wall blocks 100 are placed side by side with the lips 120 in
engagement,
while the lateral edges 115 of the rear faces 114 are placed closer to one
another as in the
straight orientation. In a curved wall of minimum radius, the lateral edges
115 of the rear
faces 114 of adjacent blocks 100 are in engagement and the blocks are placed
at the angle
a relative to one another. In order to provide the wall with a continuous rear
surface, the
width of the filler blocks 200 must then be adapted to fit within the
imaginary lines 400
defined on each side of the associated wall block 100 by the angle a, as
illustrated in Fig.
4. As will be apparent, the overall width of the filler block 200 then not
only depends on
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the angle a, but also on the depth C of the filler block 200, since the larger
the depth, the
shorter the overall length required for the block fitting between the
imaginary lines 400.
The length of the filler block 200 is then determined by the overall width X
of the wall
block 100, the protruding width Y of the lips 120, the depth B of the lips
120, the depth A
of the wall block 100 and the depth C of the filler block 200. Since the angle
a is enclosed
between the imaginary line 400 and the side wall is the same for both the wall
block 100
and the filler block 200, the minimum length D of the filler block 200, which
is required
for the filler blocks to form a continuous back wall at the smallest radius
achievable, can
be calculated according to the formula D = X-n(Y+YC/A-B), wherein n is 1 or 2
and
defines the number of lips 120 included in the wall block 100, Xis the length
of the wall
block 100, A is the depth of the wall block 100, B is the depth of the lip
120, C is the
depth of the filler block 200, Y is the length of the lip 120 and D is the
length of the filler
block 200. Thus, the length D of the filler block can vary between X (for
straight walls)
and X-n(Y+YC/A-B) (for a curved wall of minimum radius, as shown in Fig. 5).
Casting of the lip 120 can be achieved by way of a draw plate 140 (see
schematically in Fig. 9b), which is placed in the mold for the wall block. The
draw plate is
left in the mold for the filling of the mold and compression of the dry cast
mixture in the
mold and is pulled from the mold cavity prior to stripping of the block. The
use of draw
plates in the manufacture of dry cast concrete blocks is known.
The lip 120 preferably has a depth B, measured in a direction parallel to the
associated side wall 119, which is a maximum of 50%, preferably between 50%
and 5%,
most preferably between 50% and 25% of the overall depth A of the wall block
100 as
measured from the front face 112 to the back face 114 (see Fig. 3). The larger
the depth of
the lip 120, the wider a gap 117 between the front faces 112 of adjacent
stacked blocks
100 in a curved wall. Thus, in order to minimize the gap 117, it would be
preferable to
minimize the depth of the lip 120. Yet, the smaller the depth of the lip 120,
the harder it is
to manufacture the block 100 by dry casting, since the lip 120 may brake or
sag during or
after demolding and prior to complete setting of the block. Moreover, the
minimum radius
achievable with stacked blocks 100 including the lip 120 is determined by the
protruding
length Y, or overhang, of the lip 120, which is the distance the lip 120
protrudes laterally
outward from the sidewall 119 of the block 100. The larger the overhang
created by the lip
120, the smaller the minimum radius achievable. However, the larger the
overhang, the
higher the risk of the lip 120 braking or sagging during or after demolding.
Consequently,
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the range of radius achievable by adding a single lip 120 on each side of the
block 100 is
limited.
In order to address these limitations to the depth and protruding length of
the lip,
the invention also provides variant of the block 100 in which a larger total
protruding
length Y or overhang is achieved by providing a stepped lip 120 including two
or more
steps 120a, 120b, as illustrated in Figs. 10a to 10d. By dividing the total
protruding length
or overhang of the lip 120 into multiple, staggered steps 120a, 120b, the
chance of the lip
braking or sagging during or after demolding is much reduced. Each step 120a,
120b is
defined by perpendicular walls respectively parallel to the sidewall 119 and
the rear face
114 of the block 100. The protruding length of each step is preferably the
same and equal
to the total protruding length of the lip divided by the number of steps. The
outermost step
is coplanar with the front face. Any additional step is located further back
towards the rear
face 114 and provides a setback or undercut, so that the overall width of the
block
becomes progressively more narrow with each additional step. By providing the
lip with
multiple steps, the danger of braking or sagging of the lip during or after
demolding is
significantly reduced, since the tendency of the lip to brake or sag then
becomes directly
dependent on the protruding length of the largest step, rather than the
overall protruding
length of the lip. Since the potential of the lip braking or sagging during or
after
demolding also directly depends on the depth of the lip, the depth of the
outermost step
adjacent the front face 112 is preferably larger than the depth of any
subsequent step.
Moreover, the protruding length of the outermost step is preferably smaller
than the
protruding length of any subsequent step. When two steps are provided, the
protruding
length of the outermost step is preferably less than half the protruding
length of the
subsequent step.
As illustrated in Figure 10a, the block 100 in one embodiment includes an
irregularly shaped front portion 190 and a regularly shaped rear portion 195,
the front
portion including the embossed front face 112 with an irregularly shaped
contour 112a
with lateral edges 113. The block of Figure 10a further includes an
interconnecting
structure 300 for the connection of a secondary structure (not shown), such as
a setback
pin, a like concrete block, a veneer block, or a filler block, to the rear
face 114 of the
concrete block. The connecting structure is preferably a dovetail type
connection with one
or more female connector members 350 provided in a back surface of the wall
block and a
corresponding number of complementary male connector members provided on the
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secondary structure to be connected to the back surface 114. Filler blocks
when attached
by way of the interconnecting structure 300 can be used for covering any
rearward gap
created in an installed condition by the lips 120a, 120b between the block and
an adjacent
like block. A back to back attachment of a pair of like blocks by way of the
interconnecting structure 300 also allows for the assembly of a two sided free
standing
wall.
In one embodiment of the set of concrete blocks for the assembly of curved
walls
of minimum radius of curvature, the wall block 100, including the protruding
lips 120, has
an overall width X, protruding lips 120, with n=1 or 2, each lip has a
protruding width Y,
the wall and filler blocks 100, 200 have the same depth and the overall width
of the filler
block is between X and X-2nY. The wall and filler blocks may have a different
height.
In another embodiment of the set of concrete blocks, the wall block 100 has an
overall width X, including the protruding lips 120, n protruding lips 120,
with n=1 or 2
and each lip having a protruding width Y and a depth B, the wall block 100 has
a depth A,
the filler block 200 has a depth C and the overall width of the filler block
200 is between
X and X-n(Y+YC/A-B). The wall and filler blocks may have the same or different
heights.
The connecting structure is preferably in the form of a dovetail type
connection
with one or more male connector members provided on one of the wall and filler
blocks
and a corresponding number of female connector members provided on the other
of the
wall and filler blocks. Alternatively, the connecting structure may be a
separate connector
insertable into complementary recesses in the wall and filler blocks. However,
any other
connecting structure can be used, which is incorporated into or separate from
one or both
of the wall and filler blocks, as long as the connecting structure renders the
wall and filler
blocks connectable in a back-to-back orientation.
In another embodiment of the block 100, illustrated in Figures 12 to 13 as
block
100a, the block 100 is provided with an embossed front face 112, which
includes at least
one false joint 180, which may extend at an angle to the top and bottom faces
116, 118.
This provides the block with the appearance of a natural stone. In the
particular
embodiment illustrated, the false joint extends at an angle of about 45
degrees to the top
and bottom faces, but other orientations of the false joint at any angle from
0 to 45 degrees
are possible. Of course, the front face can include multiple false joints
respectively
oriented at different angles to the top and bottom faces.
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As illustrated in Figures 12 to 13, the block 100 or 100a can also be provided
with
irregularly shaped front faces 112 where at least one lateral edge 113 of the
front face
extends at an angle of up to 45 degrees to the side wall 119. Thus, in this
embodiment of
the block, the lateral edges 113 of the front face are oriented at an angle of
0 to 45 degrees
to the sidewall in order to give the block the appearance of a natural stone.
One or both of
the sidewalls 119 can also be oriented at an angle other than perpendicular to
the top and
bottom faces 116, 118, for example at an angle of 70 to 110 degrees to the top
or bottom
face. However, it is preferred that the angled sides of the block be limited
to only a front
portion 190 of the block, with a rear portion 195 of the block having parallel
sidewalls 119
perpendicular to the top and bottom faces 116, 118, for maximum stability of a
wall of
stacked like blocks.
As shown in Fig. 11, the blocks 100 with multiple steps 120a, 120b can also be
used to build curved wall, whereby the radius of the curvature achievable is
determined by
the combined protruding length of all the lips 120a, 120b at each end of the
block.
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