Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02479095 2004-08-25
a
IMPROVED BARRIER SCREEN AND METHOD FOR PROTECTING A GUTTER FROM DEBRIS
BACKGROUND
The present invention relates to barriers for preventing debris from entering
drainage
gutters but more particularly relates to a mesh screen with improved water
penetration
and burner properties. The invention further provides a method for protecting
a gutter
from ingress of debris but which allows more efficient penetration of water
through a
gutter barrier. More particularly, the invention provides an improved screen
to prevent
unwanted entry of debris such as leaves sticks branches yet improves
efficiency of
water penetration before reaching a lip of the gutter.
PRIOR ART
Barrier screens for preventing unwanted ingress of leaves sticks and other
debris
into gutters are well known. Typically barrier screens are manufactured from
metals or
plastics and comprise an array of strands usually disposed at right angles and
which
define apertures through which runoff passes. Absence of the screens causes
debris
buildup in a gutter which eventually clogs the gutter and causes blockages and
unwanted overflow of rainwater.
There are a wide variety of screens which are manufactured as a mesh to cover
an
open mouth of a gutter. Known meshes may be screw fastened generally to the
lip of a
gutter via one edge and inserted under a roof tile along the other edge.
Alternatively
the mesh may be arced so that its elastic memory causes the mesh to bias
itself in
position between internal gutter faces or between one internal gutter face and
part of a
roof such as a tile.
The objective in manufacture of mesh screens is to ensure that on one hand
debris is
prevented from entering a gutter which is protected by the screen and on the
other hand
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ensuring that water drops through apertures in the mesh before spilling over
the edge of
the gutter. The mesh configuration is critical to its performance. Mesh
apertures must
be large enough that they allow roof runoff every opportunity to overcome
surface
tension and penetrate the gutter but small enough to prevent unwanted debris
entering
the apertures. Also, the disposition of the strands is critical to achieving
these
objectives. In the case where a strand runs parallel to a line of the gutter
this will tend
to retard the flow of the runoff causing water to cascade over the
longitudinal strands.
In the case where upper strands are normal to the line of a gutter, water may
run right
over the surface of the mesh without dropping into apertures due to an
inability of the
1o runoff to overcome surface tension created by the mesh. Attempts to
overcome surface
tension by increasing aperture size have resulted in an increase in the
tendency to trap
leaf stems and sticks in the larger size apertures. It has been found that
water
penetration through the mesh increases if the aperture size is increased.
Water
penetration is also increased if strands on an upper face of a mesh screen are
normal to
Is the direction of a gutter and to strands on a lower or underside face of
the screen.
However if a longitudinal strand is too deep. This may increase the
longitudinal
stiffness of the mesh making it much harder to install. One attempt to
overcome the
aforesaid prior art problems is disclosed in Australian patent 741254 which
teaches a
mesh screen for application to guttering which is characterized in that the
thickness of
20 longitudinal strands extends for substantially the full thickness of the
mesh from the top
and also characterized in that the holes in the mesh are increased in length
in the
direction of flow of water running across the width of the guttering in a
direction at
right angles to the length of the guttering. The strands of the mesh aligned
longitudinally to the guttering project below the plane of the mesh to
facilitate water
2s removal on the underside of the mesh. Mesh screens of this type suffer from
the
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disadvantage that water is prone to flow over the lip of the gutter before
penetrating the
mesh due to surface tension rending the mesh described in that patent less
efficient than
it might otherwise be. Parameters which effect the performance of a mesh
barrier
screen include the planar relationship between lateral and longitudinal
strands,
thickness of strands in each layer, center to center spacing between strands,
depth of
longitudinal strands and lateral strands, size of apertures defined by
respective lateral
and longitudinal strands. Various attempts have been made to improve the
performance
of mesh screens for gutters to ensure that all runoff penetrates the screen,
and that no
debris enters a gutter . Satisfaction of these objectives have involved
compromise of
parameters but there is further room for improvement.
INVENTION
The present invention employs some of the known characteristics of mesh
screens but
provides an improved geometry which increase the efficiency of the mesh in at
least the
areas of water penetration and prevention of unwanted debris penetrating the
mesh.
In its broadest form the present invention comprises;
a mesh screen for providing barrier protection of a draining gutter, the
screen
comprising a generally planar length of mesh having a first face and a second
face;
wherein the first face is an outside face comprising an array of strands
disposed parallel
to each other but at an angle other than normal to a longitudinal axis of said
gutter; the
second face comprising an array of strands disposed parallel to each other and
also
parallel to said longitudinal axis of said gutter; wherein the strands on the
upper face
deflect run off water along a path which is longer than a path normal to said
longitudinal axis of said gutter, thereby allowing water to drop through
apertures in
said mesh screen anywhere along the length of the angled strands.
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Preferably, the angled strands have a cross section which provides a damming
effect on
water runoff to ensure that water is inhibited or prevented from mounting the
strands of
said upper surface.
In another broad form the present invention comprises:
a mesh screen for providing barrier protection of a draining gutter from
sticks, leaf
litter and the like, the screen comprising a generally planar length of mesh
having a
first face and a second face; wherein the first face is an outside face facing
away from
the gutter and comprising an array of strands disposed parallel to each other
and when
the mesh is mounted on a gutter at an angle other than normal to a
longitudinal axis of
1o said gutter; the second face opposing the gutter when the mesh is installed
and
comprising an array of strands disposed parallel to each other and also
parallel to said
longitudinal axis of said gutter; such that the strands on the first face and
the strands on
the second face are respectively disposed at an angle other than 90 degrees,
wherein the
strands on the upper face deflect run off water along a path which is longer
than a path
normal to said longitudinal axis of said gutter, thereby allowing water to
drop through
apertures in said mesh screen anywhere along the length of the angled strands.
In another broad form the present invention comprises:
a method for providing baxrier protection for a gutter to prevent entry of
objects such
as leaf litter sticks branches and the like, into the gutter, wherein the
barrier protection
comprises a mesh screen, the screen comprising: a planar length of mesh having
a first
face and a second face; wherein the first face is an outside face comprising
an array of
strands disposed parallel to each other but at an angle other than normal to a
longitudinal axis of said gutter; the second face comprising an array of
strands disposed
parallel to each other and also parallel to said longitudinal axis of said
gutter; wherein
the strands on the upper face deflect run off water along a path which is
longer than a
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path normal to said longitudinal axis of said gutter, thereby allowing water
to drop
through apertures in said mesh screen anywhere along the length of the angled
upper
strands.
the method comprising the steps of ;
a) placing the mesh screen over an open face of a gutter such that a first
edge of the
mesh engages a lip of the gutter and a second edge engages a roof structure;
b) securing the screen to said gutter and said roof structure,.
The present invention described herein still may employ some of the known mesh
characteristics and manufacturing techniques of the prior art save for unique
to characterizing features described. The present invention seeks to provide
an alternative
to the known barrier mesh screens by providing a screen having optimal
stiffness
properties, optimal water penetration properties and optimal barrier
properties.
It is an object of the invention to provide a double layer mesh screen which
increases
water penetration properties of the mesh by relative disposition of strands on
upper and
lower faces of the screen.
Preferably the strands of the mesh layers are made from the same material but
it will be
appreciated that strands may be made from different materials.
In another broad form the present invention comprises:
a mesh screen capable of providing a barner for protecting a drainage gutter
from
ingress of debris;
the screen comprising a generally planar sheet of mesh having a first face and
a second
opposite face; wherein, the first face comprises strands disposed parallel to
each other;
the second face comprising strands disposed parallel to each other and at an
angle other
than 90 degrees to the strands on the first face.
Preferably, the strands comprising the first face form a first layer and the
strands
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comprising the second face form a second layer of the mesh screen wherein the
second
layer lies above the first layer and provides said first face.
Preferably the first layer of strands lies along an X axis of X-Y orthogonal
axes and the
strands of the second layer lie at an angle to the Y axis of the orthogonal
axes.
The strands in the first and second layers are spaced apart and equidistant.
Two strands on said first layer and two strands on said second layer together
define an
aperture shaped as a parallelogram and the mesh overall has a plurality of
parallelogram shaped apertures formed by said strands.
The strands on the first layer and the strands on the second layer are
disposed at an
l0 acute angle to each other within the range of 30 - 70 degrees.
The first and /or second layer of strands are ovoid in cross section.
The angle of repose of the mesh strands on the upper layer is such that a
distance
traversed by each strand of said second layer between a roof edge and a lip of
the gutter
is greater than the shortest distance between the roof edge and lip of the
gutter. Runoff
from the roof adopts a path along the strands of the second layer and drops
though the
parallelogram shaped apertures at any location along the distance defined by
said
strands of said second layer of the mesh.
The strands in the second layer are preferably disposed at an angle other than
90
degrees to a line defined by the lip of the roof edge, wherein the strands
have a cross
section which provides a damming effect on water runoff to ensure that water
is
inhibited or prevented from mounting the strands of said upper surface thereby
enabling it to be retarded for sufficient time despite its velocity drop into
the apertures.
According to one embodiment the strands are ovoid in cross section.
In another broad form the present invention comprises:
a mesh screen for providing harrier protection of a draining gutter from
sticks, leaf
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litter, debris and the like, the screen comprising a generally planar length
of mesh
having a first face and a second face; wherein the first face is an outside
face facing
away from the gutter and comprising an array of strands disposed parallel to
each other
but at an angle other than normal to a longitudinal axis of said gutter; the
second inner
face opposing the gutter and comprising an array of strands disposed parallel
to each
other and also parallel to said longitudinal axis of said gutter; such that
the strands on
the first face and the strands on the second face are disposed at an angle to
each other
than 90 degrees defining a plurality of parallelogram shaped apertures,
wherein, the
strands on the upper face deflect run off water along a path which is longer
than a path
1o normal to said longitudinal axis of said gutter, thereby allowing water to
drop through
apertures in said mesh screen anywhere along the length of the angled strands.
In its broadest form the present invention comprises:
a mesh screen for providing barrier protection for a gutter to prevent entry
of objects
such as leaf litter sticks branches and the like into the gutter, the mesh
screen
I5 comprising an array of parallel spaced apart strands disposed in a first
direction and an
array of parallel strands disposed in a second direction; characterized in
that the strands
define an array of parallelogram shaped apertures which allow water to flow
therethrough.
Preferably, a first layer of strands are disposed in a longitudinal direction
and a second
2o layer of strands are disposed at an angle to said first layer of strands
between 20 - 60
degrees.
In another broad form of a method aspect the present invention comprises:
a method for providing barrier protection for a gutter to prevent entry of
objects such
as leaf litter sticks branches and the like, into the gutter, wherein the
barrier protection
25 comprises a mesh screen, the screen comprising: a generally planar length
of mesh
CA 02479095 2004-08-25
having a first face and a second face; wherein the first face is an outside
face
comprising an array of strands disposed parallel to each other but at an angle
other than
normal to a longitudinal axis of said gutter; the second face comprising an
array of
strands disposed parallel to each other and also parallel to said longitudinal
axis of said
s gutter; wherein the strands on the upper face deflect run off water along a
path defined
by the strands on the first face and which is longer than a path normal to
said
longitudinal axis of said gutter, thereby allowing water to drop through
parallelogram
shaped apertures in said mesh screen anywhere along the length of the angled
upper
strands.
to the method comprising the steps of ;
a) placing the mesh screen over an open face of a gutter such that a first
edge of the
mesh engages a lip of the gutter and a second edge engages a roof structure;
b) securing the screen to said gutter and said roof structure.
15 DETAILED DESCRIPTION
'The present invention will now be described in more detail according to
preferred but
non limiting embodiments and with reference to the accompanying illustrations
wherein:
2o Figure 1 shows a perspective view of a mesh screen according to a preferred
embodiment;
Figure 2 shows a cross sectional view of strands of an upper layer of the
screen of
figure 1.
Figure 3 shows a plan view of the mesh screen of figure 1 inverted.
25 Figure 4 shows a side profile of a mesh screen fitted over a roof and
gutter.
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Figure 5 shows a perspective view of a mesh fitted to a roof and gutter edge.
As shown in figure 1, the present invention provides a mesh screen 1 for use
with a
drainage gutter for protecting the gutter from ingress of leaf litter sticks
and other
debris. Mesh 1 comprises a first upper layer 2 formed from an array of strands
3 and a
second lower layer 4 formed from an array of strands 5. The geometry of the
mesh 1 to
be described in more detail below increases the efficiency of the mesh in at
least the
areas of water penetration and prevention of unwanted debris penetrating the
mesh.
This is in part due to the relative disposition of the strands 3 forming first
layer 2
relative to the strands 5 forming lower layer 4. As may be seen in figure 2,
upper
layer 2 comprises a first upper face 6 and lower layer 4 forms a second
opposite face 7.
Upper face 6 is formed by strands 3 disposed parallel to each other but at an
angle other
than normal to a longitudinal axis of a gutter to which the mesh 1 is
attached. The
second and lower face 7 comprises an array of strands 5 disposed parallel to
each other
and also parallel to a longitudinal axis of a gutter to which mesh 1 is
fitted. Strands 3
are disposed at an angle to strands 5 such that the apertures 8 so formed in
the mesh
form a shape resembling a parallelograms. Figure 2 shows an end view of mesh 1
formed by upper layer strands 3 which are disposed over lower layer strands 5
forming
parallelogram apertures 8. In a typical arrangement, edge 9 engages a lip of a
gutter to
2o which mesh 1 is attached. As shown in figure 1, during rainfall, water
flows along
upper strands 3 in the general direction of arrow 10. Strands 3 act as a
barrier to roof
runoff water cascading over mesh 1. According to the prior art, strands 3
would be
disposed at 90 degrees to strands 5 as it was previously thought that this
would
facilitate water travel normal to the lip of the gutter and into apertures 8.
However, it
was found that in heavy downpours and even in moderate rainfall, surface
tension was
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maintained preventing water from naturally dropping through mesh apertures so
that
some of the water passed over the mesh and thence over the gutter. This
defeated the
purpose of the mesh, as although it prevented some debris from entering the
gutter, a
substantial amount of the runoff was also excluded. In order to find a
compromise, the
inventors found that if the distance the water travels before it reaches the
lip of the
gutter can be significantly increased, it will have an increased chance of
breaking the
surface tension as the velocity of the water will reduce due to the increased
distance it
must travel between a roof and a lip of the gutter.
Strands 3 on the upper face 6 deflects run off water along a path ( arrow 10)
which is
l0 longer than a path normal to the longitudinal axis of said gutter, thereby
allowing water
to drop through apertures 8 in the mesh screen 1 anywhere along the length of
the
angled strands 3 but before the water reaches edge 9 of screen 1. Preferably,
strands 3
are, when the mesh is in situ disposed above strands 5 such that strands 3 lie
in a plane
parallel to a plane in which strands 5 are disposed but elevated above the
latter plane.
This, together with the angle of repose of strands 3 relative to strands 5
enhance the
damming effect of strands 3 on water traveling in the direction of arrow 10.
Preferably, the angled strands 3 have a cross section which provides a damming
effect
on water runoff to ensure that water is inhibited or prevented from mounting
strands 3
of upper surface 6.
Due to the disposition of strands 3 relative to strands 5, water runoff cannot
take its
logical shortest normal ( 90 degree) path from a roof line to a lip of a
gutter as it is
deflected along a predetermined angle. According to one embodiment, strands 3
have
an elliptical shape but it will be appreciated that other cross sectional
shapes may be
adopted. It will also be appreciated that strands 3 may be rotated 90 degrees
from the
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angle shown in figures 2 and 3 so that strands 3 travel towards edge 9 from
left to right
instead of from right to left. According to the prior art mesh, apertures were
elongated along a line normal to the longitudinal direction of the gutter to
which the
mesh was attached. It was thought this would decrease surface tension of
runoff and
increase the prospects of penetration of water through the elongated holes to
prevent
skimming over the upper surface of the mesh. This increased the risk of sticks
and
debris entering the larger apertures. The parallelogram shape of the apertures
8 of mesh
1 does not increase the potential for unwanted leaves, sticks and debris
entering
apertures 8 but the disposition of strands 3 substantially reduces or
eliminates water
1o escape over the end of edge 9. Size of aperture 8 may be varied according
to the
number of strands 3 disposed per unit area or length of mesh. A reduced number
of
strands 3 will increase size of aperture 8. Likewise a reduced number of
strands 5 will
also increase aperture size. The size of apertures 8 may be determined
according to
prescription but strands 3 should be disposed at an acute or oblique angle to
strands 5
to maintain a runoff path which is longer than a path where runoff travels
normally to
the line of a gutter. Taken over the area of the mesh there is a substantial
retardation of
runoff so that most if not all water running over upper surface 6 of mesh 1
may enter
apertures 8 before it would otherwise jump off the lip of the gutter.
The improved mesh herein described is preferably manufactured from an extruder
2o which includes oblique passages which result in production of oblique/
angled strands
3.
The mesh screen provides barrier protection of a draining gutter from sticks,
leaf litter
and the like, the screen comprising a generally planar length of mesh having a
first
face and a second face; wherein the first face is an outside face facing away
from the
gutter and comprising an array of strands disposed parallel to each other but
at an angle
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other than normal to a longitudinal axis of said gutter. The second face
opposes the
gutter and comprises an array of strands disposed parallel to each other and
also
parallel to the longitudinal axis of the gutter. The strands on the first face
and the
strands on the second face are disposed at an angle to each other, other than
90 degrees,
wherein the strands on the upper face deflect run off water along a path which
is longer
than a path normal to said longitudinal axis of the gutter, thereby allowing
water to
drop through parallelogram shaped apertures in the mesh screen anywhere along
the
length of the angled strands.
Preferred dimensions of the strands and aperture sizes are as follows:
1o Thickness of strands ( longitudinal) 0.5-3mm
Thickness of strands ( diagonal ) 0.5 - 3mm
Strand spacing ( longitudinal) 4 - 9mm
Strand spacing ( longitudinal) 3 - 9mm
Aperture size Major axis 4- ~mm
Aperture size Minor axis 4- hrnm
The mesh is proportioned to satisfy the objectives of optimal water flow over
an upper
surface of the mesh, slip off of debris such as leaves and pine needles and
maximizing
ingress of runoff water through the apertures and into a gutter.
Suitable materials for the mesh strands are for example, high and /or low
density
2o polyethylene. The mesh is preferably constructed so that upper diagonal
strands
disposed at an angle to a roof line provide a damming effect whereas the lower
strands
which run parallel to the roof line are smaller than the upper strands to
allow optimal
ingress of water through the mesh and into the gutter.
The method of installation of the mesh may comprise the steps of ;
a) placing the mesh screen over an open face of a gutter such that a first
edge of the
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mesh engages a lip of the gutter and a second edge engages a roof structure;
b) securing the screen to said gutter and said roof structure.
c) ensuring that upper strands are at an acute or oblique angle to lower
strands , the
latter being disposed parallel to a longitudinal axis of a gutter.
The present invention seeks to provide an alternative to the known barrier
mesh screens
by providing a screen having optimal stiffness properties, optimal water
retardation and
penetration properties and optimal barrier properties. It is an object of the
invention to
provide a double layer mesh screen which increases water penetration
properties of the
mesh by relative disposition of strands on upper and lower faces of the
screen.
to Preferably, the strands of the mesh layers are made from the same material
but it will
be appreciated that strands may be made from different materials. The
elevation or
diameter of respective strands may be the same for the upper and lower strands
or they
may be of different elevations or diameters.
Figure 2 shows a cross sectional view of strands of an upper layer of the
screen of
figure 1. Figure 3 shows a plan view of the mesh screen of figure 1 inverted
so that the
angled upper layer 6 is shown on the bottom.
Figure 4 shows a side profile of a mesh screen fitted over a roof and gutter.
Mesh
screen 20 has the characteristics previously described and is typically fitted
at end 21
under roof tile 22 and over roof tile 23 . Opposite end 24 is fitted over
gutter 25 near lip
26.
Figure 5 shows a perspective view of a mesh 30 fitted to a roof structure 31
and gutter
32. Water runoff on roof surface 33 travels in the direction of arrow 34
engaging
upper strands 35 which deflects the runoff, which would usually travel normal
to the
line of the gutter, to an angle off normal and defined by upper diagonal
strands 35.
Since the strands 35 are disposed at an angle to a normal to the gutter, flow
of runoff is
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directed over a longer distance across the mesh and along strands 35 retarding
flow
long enough so that all the runoff will fall through the apertures 36 in the
mesh 30.
It will be recognized by ,persons skilled in the art that numerous variations
and
modifications may be made to the invention as broadly described herein without
departing from the overall spirit and scope of the invention.
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