Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND DEVICE FOR CLEANING TRASH RACKS
FIELD OF THE INVENTION
The present invention relates to the field of trash racks or screens and is
particularly concerned with a method and device for cleaning trash racks or
screens.
BACKGROUND OF THE INVENTION
Mechanical bar screens are frequently used in a variety of circumstances, for
example, to prevent debris from entering a pump, a turbine, a water treatment
device
or other liquid dependent apparatus. Indeed, canals, irrigation channels and
the like
are frequently contaminated with so-called "natural" debris such as the limbs
of trees,
blocks of ice and like and with so-called "man-made" debris such as tires,
bottles and
the like. If such debris were permitted to enter a water dependent apparatus,
such
apparatus could be severely damaged or ruined.
In order to protect water dependent apparatus, it is common practice to mount
a mechanical bar screen commonly referred to as a trash rack in the liquid,
upstream
from the apparatus to be protected. Such trash racks usually include a
plurality of bars
in closely spaced, side-by-side relationship relative to each other so as to
define a
corresponding plurality of relatively narrow and elongated flow openings. The
flow
openings typically have a width narrower than the width of solid material to
be
screened so as to allow for separation of the solid materials from the liquid
flow
stream.
One of the disadvantages associated with the use of conventional trash racks
is
that they have a tendency to become clogged with trash and other debris so as
to
eventually severely restrict or even terminate the flow of water to the pump
or other
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apparatus. A recurrent cleaning of the trash rack therefore has to be
performed in
order to maintain proper flow to the pump, turbine or other water treating
apparatus.
The prior art shows various examples of devices specifically designed for
cleaning so-called trash racks. Some of these devices are particularly
complex. For
example, U. S. Patent 4,107,040 discloses a rake member which is moved along
an
asymmetric S-shaped curve by a plurality of articulated arms and driven chains
which
are passed around a number of chain wheels to generate the asymmetric S-shaped
curve. While the device may positively engage a bar screen, it is somewhat
unwieldy
and occupies a rather large volume. Various other rather mechanically complex
trash
racks are shown in the prior art. These mechanically complex trash rack
cleaning
devices have failed to provide satisfactory results, at least in part because
of their
inherent tendency towards mechanical failure and breakdown. Furthermore, their
inherent somewhat prohibitive cost has rendered them unpopular. Hence, in the
competitive field of trash rack cleaning devices, mechanically complex
structures have
failed to provide adequate results and generally have not succeeded
commercially.
Two types of trash rack cleaning devices having simpler structures have
succeeded in obtaining at least a partial commercial success. The first so-
called
"cable" type of structure is exemplified by the invention described in the
Swiss patent
specification No. 396,779. This type of structure includes a carriage
suspended from a
lift wire in abutting contact with the trash rack. The carriage is provided
with teeth
extending between the bars of the trash rack. A bucket is hingedly mounted to
the
carriage. When the carriage is allowed to drop by the action of gravitational
forces,
the bucket is pivoted away from the trash rack. When the carriage is pulled
upwardly
by the lift wire, the bucket collects the trash which has been gathered at the
trash rack.
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Although more reliable and less costly than the above-mentioned mechanically
complex structures, the so-called "cable" type of the trash rack cleaning
devices using
raking components suspended by hanging wires suffer from at least two major
drawbacks. First, since the wires are by nature relatively flexible and since
the device
relies on gravitational force for lowering the raking component, the latter
may be
impossible to lower when it encounters an obstacle during its descending
action.
Furthermore, when relatively large solid debris is present adjacent the
surface of the
liquid, the lack of downward pushing force may not allow the raking component
to get
at the debris in an attempt to move it as a whole.
A second major drawback associated with the so-called "cable" type of
cleaning devices is that they are susceptible to being affected by side
streams. The
problem is compounded by the fact that such side streams are particularly
prevalent
when trash racks become obstructed.
A second type of cleaning device presenting a relatively simple structure and
having achieved some commercial success is the so-called "arm" type of
cleaning
device. The arm-type cleaning device is exemplified by the structure disclosed
in
Swedish patent specification No. 302,430 and Canadian Patent No. 1,115,646.
Swedish patent specification No. 302,430 discloses a device including a rake
member mounted at the distal end of a rake arm. An hydraulic mechanism is used
to
lower the rake adjacent the bottom of the rack with the rack member spaced
from the
latter. The rake member is then pressed against the trash rack before the rake
arm is
lifted, thus lifting the trash gathered at the trash rack towards a disposal
container or
chute.
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Canadian Patent No. 1,115,646 discloses a trash rack cleaning device which
attempts to overcome some of the above-mentioned inherent drawbacks. The
structure disclosed in Canadian Patent No. 1,115,646 includes a rake member
having a
generally wedge-shaped body defined between wedge forming surfaces. The rake
member is pivotally mounted at a distal end of the rake arm. An hydraulic
mechanism
is used for moving the rake arm along the trash rack and for pivoting the rake
member
between a scraping configuration assumed during downward movement of the rake
arm and a scooping configuration assumed during the upward movement of the
rake
arm.
In the scraping configuration, the rake member is angled so that it engages
the
trash rack only with its apex, thus showing the trash gathered at the trash
rack and
allowing some of the smaller debris to pass between the trash rack bars. In
the
scooping configuration, the rake member has one of its surfaces pressed flush
against
the trash rack and another of its surfaces scoops the remaining trash
upwardly.
Although the above-mentioned structure succeeds in allowing some of the
smaller debris to flow through the trash rack bars, in situations wherein the
debris is
clogged together or wherein the debris is relatively large, this strategy may
not always
be successful and, hence, the inherent operational demands of the device are
such that
the device must be oversized to account for situations wherein large debris
obstructs
the trash rack. Indeed, it must be sized so as to be able to push on
relatively large and
heavy debris. Furthermore, in some situations, it may not be desirable to
allow smaller
debris to flow between the trash rack bars since such smaller debris may
damage the
downstream equipment such as turbines, pumps or the like.
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As outlined above, one of the major drawbacks associated with prior art
cleaning devices is that the inherent operational demands are such that they
must be
oversized to withstand the mechanical stresses that are seldom encountered.
Thus, not
only is the device oversized for most of its working cycles but a considerable
amount
of energy is wasted moving oversized components during the cleaning cycles.
Indeed,
since such devices must clean the trash rack by upwardly scooping the debris,
they
must access a position underneath the debris. In order to do so, they must be
sized so
as to be able to travel through relatively solid and large obstacles.
Furthermore, in the
event that the debris forms a large accumulation, the device must be sized to
withstand
the forces generated by the weight of the whole pile.
One of the main advantages of the present invention resided in that the
nibbling
capacity of the device allows the latter to divide relatively large debris
into smaller
debris and thus eliminates the need for oversizing the device so as to be able
to clean
relatively large debris that are only seldom encountered. The nibbling
operation can
also be performed for allowing the raking component to travel through
relatively large
solid obstacles during its cleaning cycle.
SUNINIARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved
method and device for cleaning trash racks.
It is a further object of the present invention to provide a cleaning device
for
trash racks that can be used to efficiently remove debris from a trash rack.
A further object of the present invention is to provide a cleaning device for
trash racks that prevents debris from accumulating near the bottom of the
trash rack
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when its rake component is used as a scraper in a downward movement to scrape
debris having adhered to the trash rack.
A still further object of the present invention is to provide a cleaning
device for
trash racks that has a built-in means for customizing the distance between its
rake
component and the trash rack so as to compensate for inherent variations in
trash rack
design and manufacturing precision.
A still further object of the present invention is to provide a cleaning
device for
trash racks that conforms to conventional forms of manufacturing, is of simple
construction and easy to use so as to provide a trash rack cleaning device
that is
economically feasible, long-lasting and relatively trouble-free in operation.
According to one aspect of the present invention, there is provided a cleaning
device for removing debris located adjacent a trash rack, the trash rack
including at
least two trash bars positioned in a relatively parallel relationship relative
to each other
so as to define at least one corresponding flow channel therebetween, the
cleaning
device comprising a device mounting base for mounting the device adjacent the
trash
rack; a longitudinally extending member movably mounted on the device mounting
base, the longitudinally extending member having a first end and a
longitudinally
opposed distal end; drive means for moving the longitudinally extending member
relative to the device mounting base in a direction generally parallel to a
longitudinal
axis of the longitudinally extending member, a debris collecting means for
collecting
the debris, the debris collecting means being mounted on the longitudinally
extending
member adjacent the distal end, the debris collecting means including a fixed
jaw
mounted on the longitudinally extending member and a mobile jaw movably
connected
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to the fixed jaw by a jaw connecting structure, the jaw connecting structure
allowing
the mobile jaw to both pivot and move linearly with respect to the fixed jaw.
In a preferred embodiment, the fixed jaw has a fixed jaw bottom wall and a
pair
of fixed jaw side walls extending therefrom, an axle mounted on the fixed jaw,
the
mobile jaw being pivotably mounted on the axle, an axle guiding means for
allowing
the axle to move within the axle guiding means to thereby permit the mobile
jaw to
move linearly with respect to the fixed jaw.
In one particular embodiment, the fixed jaw has a fixed jaw bottom and a pair
of fixed jaw side walls extending therefrom, a guiding means including a pair
of
guiding slots formed in each of the fixed jaw side walls, the axle extending
between the
fixed jaw side walls and being located at opposed longitudinal ends thereof,
the axle
being respectively inserted within corresponding guiding slots.
Preferably, each of the guiding slots has a generally L-shaped configuration
defining a slot proximal segment extending in a direction generally parallel
to the fixed
jaw bottom wall and a slot distal segment extending at an angle relative to
the slot
proximal segment in a direction away from the fixed jaw.
BRIEF DESCRIPTION OF TIDE DRAWINGS
An embodiment of the present invention will now be described, by way of
example, in reference to the following drawings in which:
Figure l, in a front perspective view, illustrates a trash rack cleaning
device in
accordance with a first embodiment of the present invention mounted at a water
intake
plant;
Figure 2 is an enlarged view of the trash rack cleaning device shown in
Figure l;
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Figure 3 is a front perspective view of a trash rack cleaning device removed
from the mounting rail;
Figure 4 is a rear perspective view thereof;
Figure 5 is a front perspective view of the arm and rake portion of a trash
rack
cleaning device;
Figure 6 is a rear perspective view thereof;
Figure 7 is a side elevational view, partially in cutaway, of the arm and rake
components of the trash rack cleaning system;
Figures 8, 8A and 8B are views illustrating the elongation and retraction of
the
arm segments of the arm and rake components;
Figure 9 is a rear perspective view of the rake component of the trash rack
cleaning device;
Figure 10 is a side sectional view of the rake component with the mobile jaw
in
a completely retracted position;
Figures 1 l, 11A and 11B are side views schematically illustrating the motions
for removal of debris from a trash rack;
Figure 12 is a sectional view of the rake component with the mobile jaw in a
partially opened position;
Figure 13 is a side sectional view showing the progression of the opening of
the
mobile jaw;
Figure 14 is a side sectional view illustrating the mobile jaw in a fully open
position;
Figure 1 S is a rear perspective view of a further embodiment of a trash rack
cleaning device according to the present invention;
s
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Figure 16 is a front perspective view thereof;
Figure 17 is a front perspective view of the embodiment of Figures 15 and 16
mounted on guide rails; and
Figure 18 is a side elevational view thereof.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figure l, there is shown, in a perspective view, a trash rack
cleaning device 10 in accordance with a first embodiment of the present
invention.
The cleaning device 10 is shown mounted on a platform 12 part of a liquid
treating
plant 14. The platform 12 is positioned adjacent a water intake 16. It should
be
understood that the water intake 16 could be a turbine intake, a fresh water
intake, a
waste water purifying plant intake or any other suitable water intake without
departing
from the scope of the present invention.
A conventional trash rack 18 spans across the water intake 16. The trash
rack 18 includes an array of bars 20 positioned in a relatively parallel
relationship
relative to each other so as to define substantially elongated flow channels
22
therebetween.
The cleaning device 10 includes a carriage component 24 slidably mounted on a
base component 26 so as to allow translational travel thereacross. In a
preferred
embodiment of the invention, the base component 26 includes a pair of
elongated
guiding rails 28 that are fixed in a parallel and spaced apart relationship
relative to each
other on the platform 12. In situations wherein the base member 26 is
positioned
adjacent a side wall 30 part of the water treatment plant 14, a mounting
bracket 32
may extend integrally from a lower surface of the guiding rails 28 adjacent
the
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longitudinal end thereof so as to further stabilize the guiding rails 28 on
the platform 12.
Referring now more specifically to Figures 3 and 4, there is shown in greater
details the cleaning device 10 removed from its base 26. The carriage
component 24
typically includes a base main platform 34 having a generally rectangular
configuration.
A set of wheels 36 are preferably mounted underneath the base main platform
34. Wheels
36 are configured and sized so as to be able to roll on the rails 28. A set of
wheel support
brackets 3 8 are also preferably mounted on the base main platform 34 so as to
cooperate
with the rails 28 to guide the carriage component 24 on the guiding rails 28
and to hold
down the device during its operation.
Carriage component 24 further includes a carriage frame 40 extending
substantially
upwardly from the carriage main platform 34. The supporting frame 40
preferably
defines a frame rear section 42 extending substantially perpendicularly from
the frame
main platform 34 and a frame front section 44 having a bracket 41 and a front
wall 43
extending at an angle relative to the frame main platform 34 so that the upper
section of
the frame front section 44 extends towards the frame rear section 42. A frame
auxiliary
platform 46 extends sidewardly from the frame main platform 34. The frame
auxiliary"
platform 46 is provided with hand rails 48. The frame auxiliary platform 46 is
configured
and sized to receive an intended user and is provided to allow such an
intended user
access to the device 10 while being supported on a rigid structure.
A longitudinally extending member or means comprising an arm component 50 is
mounted to the carriage component 24. In the illustrated embodiment of the
invention,
the arm component 50 is mounted to a protective casing 52 fixed to the
carriage frame 40.
The protective casing 52 protectively encloses mechanic and/or
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hydraulic components that are used to control the device 10 as will be
hereinafter
disclosed. In a preferred embodiment of the invention, the arm component 50 is
not
only fixed to the protective casing 52 but pivotally mounted on the latter by
an arm
pivotal bracket 54. When the arm component 50 is pivotally mounted to the
carriage
component 24, an arm pivoting means for pivoting the arm component 50 about
its
corresponding arm pivotal bracket 54 is also provided. The arm pivoting means
preferably takes the form of an arm pivoting piston 53 extending between a
pair of
pivoting piston mounting brackets 45, 58 respectively mounted on the carriage
component 24 and the arm component 50.
The arm component 50 is illustrated more specifically in Figures 5 through 7.
The arm component 50 defines an arm proximal end 51 and a longitudinally
opposed
arm distal end 55. Debris-manipulating means for manipulating debris
positioned on or
adjacent the trash rack 18 is mounted on the arm component 50 adjacent the arm
distal
end 55. The arm component 50 is preferably provided with an arm length
adjustment
means for adjusting the distance between the arm proximal end 51 and the arm
distal
end 55. In a preferred embodiment of the invention, the arm length adjustment
means
takes the form of at least two arm segments that are telescopically mounted
relative to
each other. The arm component 50 thus preferably defines an outer segment 57
and at
least one arm inner segment 60. It should be understood that the arm component
50
could include a plurality of arm inner segments 60 without departing from the
scope of
the present invention. The arm inner segment 60 is slidably inserted at least
partially
within the arm outer segment 57.
A motor means 62 is mounted preferably on the arm outer segment 57. The
motor means 62 is mechanically coupled to an output shaft 64 having a driving
gear 66
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mounted thereon. The driving gear 66, in turn, is mechanically coupled to a
pair of
driven gears 68. The driven gears 68 are, in turn, mechanically coupled to a
driving
chain 70. The driving chain 70 extends between a pair of driving chain pulleys
72 and
74 respectively mounted on both ends of the arm inner segment 57. When driving
chain 70 drives the arm into an extended position, a first auxiliary chain 76
rotates on
gear 82 between the two pulleys 80 and 81. This motion drives a second
auxiliary
chain 77 that rotates on gear 83 between pulleys 84 and 78. The motion of the
arms
activates movement of the hydraulic hoses 85.
The debris-manipulating means is illustrated more specifically in Figures 9
through 14. The debris-manipulating means 56 includes a fixed jaw 84 and a
moving
jaw 86. The fixed jaw 84 is adapted to be rigidly mounted to the distal end 54
of the
arm component 50. The fixed jaw 84 preferably includes a fixed jaw bottom wall
88
having a fixed jaw rear wall 90 and a pair of opposed fixed jaw side walls 92
extending
substantially perpendicularly from its peripheral edges. A scraping blade 94
preferably
having a generally frontwardly beveled configuration is rigidly mounted to the
fixed
jaw bottom wall 88 adjacent its front peripheral edge 96. Both the fixed jaw
84 and
the mobile jaw 86 are preferably provided with jaw slots 124 formed therein
for
allowing true flow of water therethrough while retaining debris.
The debris-manipulating means 56 also includes a jaw moving means for
moving the mobile jaw 86 relative to the fixed jaw 84. The jaw moving means
typically takes the form of at least one and preferably two jaw moving
cylinders 98 that
are mounted on the fixed jaw back wall 90 by mounting brackets 100 and extend
through the latter.
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The jaw moving cylinders 98 are also connected to the mobile jaw 86 so as to
provide movement to the latter. The mobile jaw 86 preferably has a generally
concave
configuration typically defined by a mobile jaw top wall 102 that extends
integrally and
at an angle with a mobile jaw front wall 104. The mobile jaw 86 also
preferably
includes a pair of opposed mobile jaw side walls 106.
The mobile jaw 86 is mounted so as to be pivotable relative to the fixed jaw
84.
In the illustrated embodiment of the invention, a jaw pivoting axle 108
extends
between a protruding section of the fixed jaw side walls 92. A pair of spaced
apart
mobile jaw mounting brackets 110 typically having a generally U-shaped cross-
sectional configuration are mounted on both the mobile jaw top wall 102 and in
an
overriding relationship relative to the jaw axle 108, so as to allow pivotal
movement
between the mobile jaw 86 and the jaw axle 108.
One of the main features of the present invention is that in a preferred
embodiment of the invention, the mobile jaw 86 is mounted on the fixed jaw 84
so as
to allow not only for relative rotation of the jaws 84 and 86, but also so as
to allow for
a predetermined linear movement between the fixed jaw 84 and the mobile jaw
86. As
can be seen, the jaw axle 108 is preferably slidably mounted at each
longitudinal end
thereof within a corresponding axle guiding bracket 112. Each axle guiding
bracket
112 has an axle slot 114 formed therein for slidably receiving the
longitudinal end of
the jaw axle 108 and guiding its translational movement. Each slot 114
preferably has
a slanted L-shaped configuration so as to provide a substantially cam-like
action. It
will be understood that the term linear movement includes movement in any
plane or
combination thereof.
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The mobile jaw 86 is thus adapted to pivot about the jaw axle 108 between a
jaw opened configuration and a jaw closed configuration wherein its distal
peripheral
edge 116 abuttingly contacts the blade 94. Also, the mobile jaw 86 is adapted
to move
linearly relative to the fixed jaw 84 between a retracted position illustrated
in Figure 10
and a fully extended position shown in Figure 14 wherein the jaw axle 108
pushes the
mobile rotating jaw 86 towards the distal segment of the slot 114. Thus, in a
jaw
extended position, the distal edge 116 of the mobile jaw 86 is in a spaced
relationship
relative to the blade 94. The combination of the rotational and linear
movement of the
mobile jaw 86 relative to the fixed jaw 84 aids in the efficient operation of
the device.
A slot cover plate 118 is preferably mounted on the exterior surface of the
fixed jaw side walls 92 in an overlying relationship with the external surface
of the
guiding plates 112 so as to prevent debris or other foreign objects from
exteriorly
penetrating within the slot 114 and blocking the latter. Also, a cylinder-
protecting
plate 120 preferably extends rearwardly from the mobile jaw 86 in an overlying
relationship relative to the latter.
A biasing means for biasing the mobile jaw 86 towards the mobile jaw closed
and retracted configuration illustrated in Figures 9 and 10 is preferably also
provided.
In one embodiment of the invention, the jaw biasing means may take the form of
spring pads 121 mounted on a pair of corresponding rods 122 that extend from
the
brackets 110. Thus, as shown in Figure 13, spring pads 121 are in a compressed
condition to exert the aforementioned biasing force on mobile jaws 86.
Referring to Figures 15 through 18, there is shown a trash rack cleaning
device 10' in accordance with a second embodiment of the present invention.
The
cleaning device 10' is substantially similar to the cleaning device 10 and
thus similar
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reference numerals will be used to denote similar components. One of the main
differences between the cleaning device 10' and the cleaning device 10 resides
in that a
pair of arm members 50' instead of the single arm member 50 form the
longitudinally
extending member or means. The use of two arm members 50' instead of a single
arm
member 50 allows the arm members 50' to be extended over a relatively great
length
without the risk of warping or being otherwise damaged. In other words, the
use of two
arm members 50' increases the overall structural stability and rigidity of the
device 10' so
as to allow for device 10' to dislodge debris located relative deep and even
within
relatively turbulent flows without the risk of having the arm component being
damaged.
Arm members 50' are pivotably mounted as indicated by reference numeral 51'.
In use, the carriage component 24 is moved along the rail 26 until the
carriage
component.24 is in a substantially overlying relationship relative to the
trash rack 18. The
arms 50 and 50' are then extended so that the debris-manipulating means 56 is
positioned
adjacent the trash rack 18. The pivotal movement about the arm distal end 54
allows for
compensation of the variations in the specifications of the trash rack and
associated
structure upon which the device 10 or 10' is to work. .In other words, the
pivotal action of
the arm component 50 or 50' about the arm distal end 54 allows for ideal
positioning of
the debris-manipulating means 56 on the trash rack 18 regardless of the
variations that
may occur either during manufacturing, insulation or actual use of the trash
rack 18. By
providing an ideal positioning of the debris-manipulating means 56 on the
trash rack 18,
the devices 10 and 10' reduce wear on both the trash rack 18 and the cleaning
device
itself. Hence, it increases longevity of
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both the trash rack and the cleaning device and improves the efficiency of the
cleaning
operation.
Another feature of the present invention resides in the specific construction
of the
arm components 50 and 50' that can be lowered into a relatively turbulent
current and at a
relatively great depth with minimal danger of warping or otherwise damaging
the
components. The arm components 50 and 50' may be lowered towards the bottom of
the
trash rack 18 while the blade 94 scrapes the trash rack 18 with a suitable
pressure.
Another main feature of the present invention resides in the fact that once
the
debris-manipulating means 56 has reached the position adjacent the bottom of
the trash
rack 18, the jaw moving cylinders 98 are activated so that the mobile jaw 86
moves
linearly and pivo t n open configuration about the slot 114 as shown in Figure
1 1A.
The linear action of the mobile jaw 86 allows the latter to reach and grasp
debris that has
been pushed by the blade 94 away from the latter. Hence, contrary to prior art
devices,
the mobile jaw 86 ensures that all the debris having been scraped by the blade
94 can be
reached.
The mobile jaw 86 is then retracted towards its closed configuration
illustrated in
Figures 8 and 9 by the biasing means or otherwise and as illustrated in Figure
11B. Once
the mobile jaw 86 is in its closed configuration, the arm components 50 and
50' pull the
debris-manipulating means 56 towards the surface of the volume of liquid as
shown in
Figure 11C. The debris contained within the debris-manipulating means 56 can
then be
discarded in a usual manner.
One of the main advantages of the present invention resides in that the
nibbling
capacity to allow the device to divide relatively large debris into smaller
debris and
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thus eliminates the need for oversizing the device so as to be able to clean
relatively
large debris that are only seldom encountered. The nibbling operation can also
be
performed for allowing the raking component to travel through relatively large
solid
obstacles during its cleaning cycle.
17
