Note: Descriptions are shown in the official language in which they were submitted.
1 FIELD_OF_THE_INVENTION
This invention relates to bar screens used to filter
solid substances commonly carried in the liquids of waste
waterways or sewage drainage canals.
BACKGROUN~ OF_THE INVENTION
In the past, various devices have been proposea for
cleaning and maintaining bar screens in suitable operating
condition. It is important that screens remain clean to
ensure the waterway does not become obstructed due to material
accumulating on the bar screen. If such accumulation does
occur, the waste waterway may back-up and cause flooding of
the upstream area. In order to minimize this occurence, a
number of automatic cleaning devices have been proposed that
are timed to clean the bar screen on a regular basis. In a
number of these devices, such as that disclosed in Canada
Patent 1,064,405; a rake member is inserted through the bar
screen and projects beyond the bars, such that when it is
drawn upwarà, any accumulated material on the bar members is
removed. However, if large objects have accumulated at the
base of the bar screen the rake is prevented from being fully
inserted through the bar screen. This prevents the rake from
cleaning the full height of the bar screen and the large
objects remain at the base of the screen. Furthermore,
aepending on the exact design of the cleaning apparatus,
damage to the rake may occur when large objects are
encountered.
The present invention is aesigned to overcome a number
of the problems of the prior art systems by providing a
modified bar screen that minimizes the problems caused by
large objects.
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1 SUMMARY OF THE INVENTION
The present invention provides an improved bar screen
for use in filtering a liquid in a waste waterway. This
screening device is used in conjunction with a device designed
to clean the bar screen which includes a rake means which is
inserted between the bar members of the screen and drawn upward
to clean these members. The bar screen comprises a plurality
of members having a base component adapted for securement to
the bed of the waste waterway and an upright component attached
to the base component to form an approximate L shape. These
bar members are spaced apart and positioned across the waste
waterway to provide a screening device for filtering solid
components from the liquid. The screening device is orientated
in the waterway to provide a protected area free of large
debris allowing the rake means to be inserted between the bar
members during the cleaning cycle.
According to another aspect of the invention, the
upper edge of the base component of the bar screen is at the
approximate level of the portion of the bed of the waterway
immediately upstream of the cleaning system, and the bed of
the waterway immediately downstream of the cleaning system is
lower. A height differential is established across the bar
screen and the base component of the bar functions as an
additional screening surface.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in
the drawings wherein:
Figure 1 is a side elevation of the bar screen and
cleaning apparatus;
! Figure 2 is a perspective view of the bar screen
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1 and rake of the cleaning apparatus.
Figure 3 is a sectional view of the bar screen adapted
for use in a manhole.
DETAILED DESCRIPTION OF THE PREFERRED E~BODI~ENTS
The cleaning apparatus as shown comprises a main frame
2 having four upright guide channels 4 positioned rectangularly.
A ~ shaped motor carriage member 6 is adapted with wheels 8 which
work in conjunction with the U-shaped guide members 4 to allow
the carriages to move vertically within the main frame. A motor
10 is secured to the carriage and drives a pinion gear 12 which
works in conjunction with the rack 14 for positioning the carriage
within the main frame.
Pivoted to the outer peripher~r of the T member 6 is
the rake 27. The rake comprises vertical Members 18 and a number
of finger members 20. A rake positioning channel 22 works in
conjunction with the wheel supports 24, journaled a distance below
the pivot connection 26 which secures the vertical support member
of the rake 18 to the carriage 6. This rake guide channel 22
allows the rake to be moved rearwardly away from the forward
guide channels 4 and behind the bar screen 28. As the carriage
continues to move downward, the rake reaches the bottom portion
of the guide means 22 and is urged forward between the individual
bars of screening member 28 due to the influence of gravity.
This pivoting of the rake forward is enhanced due to the lever
arm 30 and weights 32 which are secured to vertical members18.
Therefore, as the wheels 24 reach the lower portion of the guide
means 22 the rake swings forward and betw~en the bar members of
the screen 28.
As can be seen in Figure 1, each bar member is
essentially L shaped, and comprises a base cGmponent 40 and an
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1 upright component 42. ~he base component 40 has a height that
is sufficient to ensure that the finger members 20 of the rake
are inserted between the base components 40 and below the upper
surface of the base component. After the rake is positioned
between the bar members, the carriage is advanced upwardly and
the rake is drawn upwardly between the bar members an~ material
on the screening device is raised with the rake member. The
rake member continues its ascent upwardly following the forward
guide channels 4 and any swinging of the rake is limited due to
the wheel support 24 interacting with the guide channel 4. As
the rake continues upwardly, it encounters a wiper 50 which
interacts with the fingers of the rake member to remove debris.
The wiper is hinged near the back of the frame and is advanced
over the fingers as the rake moveC upward. The debris is pushed
towards a chute member 55 and subsequently, to a retaining bin
58. Within ihe rake quide means 22 is a flap member which is
hinged such that the rake follows the guide member 22 on descent
and pushes the flap member back as the rake is advanced to its
upper vertical position. Further details of the operation of the
cleaning mechanism are disclosed in Canadian patent 1,064,405.
As shown in Figures 1 and 2, the L shaped bar members are
spaced across the waterway and are aligned to allow the fingers
20 of the rake to be inserted ~etween the bars. The exact width
of the bar screen will vary according to the width of the waste
waterway and the various design considerations of the waste
waterway i.e., flow rate, expected occurence of solids, etc. As
shown, the blunt end 39 of base component 40 is positioned
upstream such that tt.e water flows across the base component
prior to contacting the upright portion. This arrangement
increases the submerged
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1 working surface and the efficiency of the device. The upper
surface of the base component provides a grate to support
the accumulation of large or heavy debris and as such provides
a protected area below the upper surface of the base component
such that the fingers of the rake may be inserted between the bars.
In a preferred embodiment of the invention, the base
component has been recessed in the bed of ~ne waterway 100 such
that the upper surface of the base component 40 and the bed of
the waterway immediately upstream are at approximately the same
level. Furthermore, the portion of the waterway downstream of the
screening member is lower such that the bed of the waterway is
essentially at the level of the lower portions of the base component
and as such provides both a grate for supporting large material
and additional filtering surfaces due to the drop across the
screening device.
It is understood that the spacing between bars will be
; a function of the material to be filtered and can be varied accord-
ingly. It can further be appreciated durlng low levels of liquid
in the waterway the flow will accelerate du~ to the drop across
the bar screen, and as such may tend to flusn out any material
that is located between the base components of the bar screen.
Although the accumulation of small material does not present a
significant problem when the rake means is inserted, this flushing
action does provide a useful function in t.;ha~ accumulation of
material may increase the possibility of corrosion of the bar
components.
The screening device can be secured to the base of an
existing waterway without providing this step profile. For example,
the bar screens could be set on the bed of a waste waterway with
the base component of each bar member prov ding a support
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1 grate for large objects. In this case, the upstream portion of
the base component could be adapted with a tapered end to
provide a somewhat smooth transition from the bed of the
waterway to the upper surface of the base component. The base
component woul~ still provide a protected area such that the
rake fingers may be easily inserted.
According to a preferred embodiment, the upright component
is not vertical and is angled slightly upstream. This
orientation of the upright component assures the rake 27 does not
bind as the rake is advanced upwardly.
It is also possible for the upstream edge of the vertical
component to be angled slightly~downstream from the vertical,
thus assuring the extension of the finger members of the rake is
constant or increasing during the clearning operation. Thus as
more debris is encountered the surface area of the finger
members is increasing, minimizing the possibility of debris
falling off the finger means.
According to Figure 2, the bar members may be fastened by
a common plate 41, at the lower extreme of the base members with
the plate subsequently secured in the waterway. However, it is
also possible for the bar members to be installed individually
when waterway is being poured and as such will be anchored
within the concrete.
This device may also be used in filtering a liquid entering
a manhole as shown in Figure 3. In this case, the water enters
the manhole 170 via conduit 72 and contacts the bar screen 28.
Depending on the velocity of the liquid, it will pass through
the upright components 42 or the base components 40. The
filtered liquid then leaves the manhole through conduit 74.
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1 According to this application, the base component may
be orientated to form an acute angle with the upright component
thereby urging filtered material to accumulate adjacent the
juncture of these components. As in the previously described
applications of the device, the bar screen provides a protected
area for easy insertion of the rake during the cleaning cycle as
well as providing an increased filtering surface. Side plates
76 assure the liquid passes through the screening device.
The exact width of the screening member will depend on
the application of the device, however, it normally will be
designed to transverse the width of the waste waterway and filter
the entire stream. As shown in Figure 2, there are a number of
upright components of reduced height, providing an emergency
overflow mechanism should a major portion of the screening device
become clogged with debris or for storm runoff. Therefore, it
is not necessary to provide an emergency divergent channel
around the filtering member, however, in some applications, this
also may be desirable.
The particular design of the bar screen members may
vary, however, they provide a protected area to allow the rake
to be inserted between the bar members. This particular structure
allows the rake means to be inserted without encountering a
large object, while also allowing the rake means to possibly
remove these large objects.
In prior art devices, vertical bar members have been
used, however, it can be appreciated as material accumulates
against these bar members, a considerable force is exerted on
these members due to the water flow striking this restriction.
The design of the present system distributes the moment caused
by this force over the length of the base component, and as
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1 such, provides a more stable structure.
Although various embodiments of the invention have been
described herein in detail, it will be understood by those
skilled in the art that variations may be made thereto without
departing from the spirit of the invention or the scope of the
appended claims.
