Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to flow restrictors for restricting
the outElow from catch basins in storm sewer systems.
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Canadian Patent No. ~,lG r ~ 707 discloses such a restrictor
in the ~orm of a specially shaped flow restricting orifice
which is secured in the entrance to an out~low pipe from a
catch basin to restrict the out~low from the latter under
storm conditions whilst mln;m; zing the risk of obstruction
due to the accumulation of debris in the catch basin.
Whilst the restrictor disclosed in this patent has proved
highly effective in terms of performing its intended
function, it has been found that its installation and main-
tenance presents some problems. The preferred embodiment
of restrictor descri.bed in the patent has a tapered tubu-
lar body portion which is pressed into the outlet pipe
from the catch basin. In order to adapt the restrictor
to the outlet pipe, a certain amount of grouting is fre-
quently necessary, as well as or instead of the sleeves
and O-rin~s mentioned in the patent. This fitting work
must be done at the bottom of a catch basin in conditions
which may be unpleasant and hazardous if an existing catch
basin is being equipped as will usually be the case. If a
restrictor must be removed for any of various reasons, sUch
as damage, a need to change the restrictor aperture, a
need to obtain access to the pipe for pipe cleaning pur-
poses,or because of blockage, the same or worse problemsarise. If a blockage has occurred, the catch basin will
likely be flooded, and must be pumped out before any work
can take place. Care must be taken when inserting or re-
inserting a restrictor that the restrictor orifice is
correctly oriented, which again entails working from the
bottom of the catch pit.
Yet a further problem arises be~ause the outlet pipes from
the catch basin fre~uently have a bend immediatel~ bey
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the opening from the basin, and will not accept the
tapered plug disclosed in the patent.
According to the invention, a flow restrictor for applica-
tion to an outlet pipe from a catch basin in a storm sewer
system comprises a frame constructed ~o be secured against
a vertically extending wall of a catch basin surrounding
A the ~ ~ aC~ to the outlet pipe, said frame presenting a
supporting surface lying in a common plane and facing awa~
from said wall, a planar restrictor plate de~ining a
restrictor orifice and having an operative position in
which one surface of the plate contacts said supporting
surface in a zone surrounding said restrictor orifice and
said outlet pipe entrance, and guide and support means or
said plate extending outwardly from said ~rame, said guide
and support means defining slots, in which lateral edges
of the plate are inserted to guide the latter for downward
movement into its operative position, and stop means for
preventing downward movement o the plate past said opera~
tive position, whereby the plate may be lowered into and
withdrawn from engagement with the ~rame from above.
With such an arrangement, and once the frame has been
attached to the catch pit wall, the restrictor plate can
be installed and removed from above, without requiring
entry to the catch basin. When the restrictor is opera-
tive to restrict flow from the catch basin, the build upo~ water in the catch basin will press the plate securely
against the frame and frame against the catch pit wall.
The restrictor opening in the plate provides a means by
which a tool or grapple can be engaged with the plate to
raise and lower it.
In order to facilitate still further the insertion and
removal of the plate, the slots defined by the guide means
preferably terminate well short of the top Q~ the plate
when in its operative position, thus reducing the distance
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through which the latter must be lifted to disengage it
from the guide means.
We have also found that the performance of the flow res-
trictor can be improved by chamfering the edges of the
restrictor orifice on that side of the restrictor plate
facing away from the catch basin. ~urprisingl~, although
the chamfering renders the orifice walls divergent, it
appears to assist in promoting a convergent flow pattern.
Further features of the invention will be apparent from
the following description of a preferred embodiment there-
of with reference to the accompanying drawings in which:
Figure 1 is a front elevation o a flow restrictor in
accordance with the invention; and
Figure 2 is a horizontal section on the line 2-2 in
Figure 1.
Referring to the drawings, a flow restrictor comprises
two main portions, a plate 2 and a ~rame 4. The frame
comprises an outer frame fabricated from L-section members
6, 8 and 10, the outwardly extending legs of which form
flanges by which the frame is secured to a vertically
extending wall W of a catch basin by means of fasteners
12 such as bolts suitably anchored in the wall W. In
order to seal the frame to the wall W, the frame may be
grouted; in this case it may be advantageous to adhere a
dressing of sand to the external surfaces of the frame.
An inner frame is formed by L-section members l~ , 18
and 20 secured within the outer frame, inwardly extending
flanges of the members providing a supporting surface
for the plate 2, lying in a common plane and facing away
from the wall W. Further flanges 24 extending from the
flanges of the members 6 and 8, outwardly of the support-
ing face, define slots 26 in which the lateral edges of
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the plate 2 are inserted to guide it for downward movement
into an operative position in which it is stopped by sup-
port means formed by the outwardly extending flange of
member 10. The slots 26 defined by the flanges 24 end
well short of the top of the frame Eor reasons discussed
further below.
The plate 2 is formed with an approximately central
restrictor opening 30 calibrated to provide a desired
degree of restriction. The shaping of this orifice is
discussed in Canadian Patent No. 1,165,207 and forms per
se no part of the present invention. It may be observed
however that the shaping is designed to provide desirable
flow control characteristics whilst also resi~ting clogg-
ing by foreign matter and limiting build up of sediment
in the catch basin. We have found that the performance
of the plate can be enhanced by orming chamfers 28 on
the edges of the orifice on the side of the plate facing
away from the catch basin. These chamfers are formed both
on the sides at thè main diamond shaped portion of the
oriice, and on the rectangular slot 34 extending down-
wardly from the bottom apex of the diamond shape. Surpris-
ingly, the presence of these chamfers appear to improve
the flow through the orifice inducing a desirable conver-
gent flow pattern, even though the passage through the
plate is divergent.
Both the plate 2 and the frame 4 may be fabricated from
type 1 polyvinyl chloride, 1120 compound.
In use, and assuming that the frame 4 has already been
secured to the vertically extending wall of the catch
basin so as to surround an opening 32 to an outlet pipe
from the catch basin, the plate 2 may be installed by
introducing the lower ends of the side edges of the plate
2 into the slots 26. The upper portions of the members 6
and 8 provide useful guides to aid such insertion. The
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plate may then be inserted until its lower edge meets the
stop provided by the member 10, thus positioning the ori-
fice 30 in front of the opening 32. ~len the catch basin
fills with an accumulation of storm water, hydrostatic
pressure will tend to press the plate against the support
surface formed by the flan~es 22, and the frame 4 in turn
will be pressed against the catch basin ~all W. Insertion
of the plate may readily be ~arried out from above, with-
out entering the catch basin.
If it is desired for any reason to remove the plate, a
suitable grapple may be lowered into the catch pit, even
if flooded, and engaged with the opening 32, and the plate
pulled upwardly until its side edges disengage from the
slots 26. By making the slots end well short of the top
of the frame, engagement and disenga~ement of the plate
is facilitated. In the event that the opening 32 has
foreign matter such as sticks jammed in it, the shortened
slots permit the plate to be pulled orwardly awa~ from
the frame before the whole of the opening has moved foul
of the frame, thus reducing the risk of jamming. Since
no part of the structure need extend into the pipe open
ing, the configuration of the latter is immaterial.
Whilst the foregoing description and the appended claims
refer or clarity to the restrictor plate as being planar,
it should be understood that moderate curvature of the
plate in one dimension would be possible provided that co-
acting parts were also similar~y curved to permit proper
cooperation of the parts as described above.
