US3872005A

US3872005A - Skimming apparatus for clarification tanks

Info

Publication number: US3872005A
Application number: US298595A
Authority: US
Inventors: Jeffrey A Baker
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1972-10-18
Filing date: 1972-10-18
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18

Abstract

This invention relates to a skimming apparatus for use in a liquid clarification tank which has a plurality of longitudinally open topped extending weir boxes that define the outlet for receiving clarified liquid. The skimming apparatus consists of a reciprocating bridge supporting an elongated blade that extends transversely of the tank and has recesses aligned with the longitudinally extending weir boxes with power means between the bridge and the blade for raising and lowering the blade. The power means define a first skimming position for the blade while the blade is in the weir box area of the tank where the lower edge of the blade is below the liquid level while the bases of the recesses are above the weir boxes and a second skimming position wherein the bases of the recesses and the lower edge of the blade are located below the liquid level. In one embodiment, the power means includes a fluid ram that has hydraulic fluid supplied thereto from a valve with switch means actuating the valve automatically when the bridge reaches a certain position and automatically moves the blade from the first skimming position to the second skimming position, as the bridge leaves the weir box area of the tank. In an alternate embodiment, the power means includes a drum on the bridge with cable means on the drum and connected to the blades. A reversible drive motor is actuated by switch means for reeling and unreeling the cable means on the drum and raising and lowering the blade.

Description

atent 1 United States Baker Mar. 18, 1975 I SKIMMING APPARATUS FOR CLARIFICATION TANKS [75] Inventor:

[52] U.S. Cl 210/141, 210/525, 210/527 [51] Int. Cl BOld 21/18 [58] Field of Search 210/143, 523, 525, 527,

[56] References Cited UNITED STATES PATENTS 1/1935 I-Iardinge 210/527 2,135,442 11/1938 Steindorf et al. 210/525 3,756,418 9/1973 Pentz et a1. 210/525 FOREIGN PATENTS OR APPLICATIQNS 728,855 11/1942 Germany 210/527 Primary ExaminerTheodore A. Granger Attorney, Agent, or Firm-Dressler, Goldsmith, Clement & Gordon, Ltd.

[57] ABSTRACT This invention relates to a skimming apparatus for use in a liquid clarification tank which has a plurality of longitudinally open topped extending weir boxes that define the outlet for receiving clarified liquid. The skimming apparatus consists of a reciprocating bridge supporting an elongated blade that extends transversely of the tank and has recesses aligned with the longitudinally extending weir boxes with power means between the bridge and the blade for raising and lowering the blade. The power means define a first skimming position for the blade while the blade is in the weir box area of the tank where the lower edge of the blade is below the liquid level while the bases of the recesses are above the weir boxes and a second skimming position wherein the bases of the recesses and the lower edge of the blade are located below the liquid level.

In one embodiment, the power means includes a fluid.

ram that has hydraulic fluid supplied thereto from a valve with switch means actuating the valve automatically when the bridge reaches a certain position and automatically moves the blade from the first skimming position to the second skimming position, as the bridge leaves the weir box area of the tank.

In an alternate embodiment, the power means includes a drum on the bridge with cable means on the drum and connected to the blades. A reversible drive motor is actuated by switch means for reeling and unreeling the cable means on the drum and raising and lowering the blade.

2 Claims, 4 Drawing Figures SKIMMING APPARATUS FOR CLARIFICATION TANKS BACKGROUND OF THE INVENTION In sewage treatment, one of the steps in the processing of the sewage involves the removal of all of the solids from the liquid before the liquid is returned to the water supply. Usually this is accomplished by gravity separation tanks wherein the liquid having solids entrained therein is fed into one end of the tank and slowly flows towards the opposite end of the tank while the solids are separated therefrom. Most of the time, the liquid that is fed to such tanks includes solids and other materials, known as scum, that have a specific gravity of less than that of the liquid and thereby float to the surface of the liquid as well as other solids that settle to the tank bottom. To remove the scum, it is customary to incorporate some type of skimming apparatus that skims the surface of the liquid while the settled solids are removed from the bottom of the tank.

In recent years, the use of rectangular gravity separation tanks has become increasingly popular. Rectangular tanks substantially simplify the construction of various portions of the sewage plant because in many instances a common wall may be employed between two different tanks. Furthermore, the rectangular tanks require substantially less space than do circular tanks, which have been standard in the industry for many years.

Because the capacity of most sewage treatment plants must be extremely high, very large rectangular final settling tanks are needed to accommodate the flow of all of the liquid while the solids are being separated therefrom.

In the use of large settling tanks, one type of outlet which has become increasingly popular includes a plurality of longitudinally extending weir boxes which are transversely spaced from each other and extend from the outlet end of the tank towards the inlet end.

In arrangements of this type, one of the problems that has been encountered is the removal of scum or other floating matter that reaches the surface of the liquid in the area of the weir system.

One arrangement for overcoming the problem of re moval of scum and other floating matter is disclosed in co-pending application Serial No. 298,506, filed October 18, 1972 by Wayne C. Bishop for a Skimming Blade and assigned to the assignee of the present invention.

SUMMARY OF THE INVENTION The present invention relates to a skimming apparatus for use in a rectangular clarification tank which has a bridge reciprocated along a path parallel to a plurality of longitudinally extending transversely spaced weir boxes that are located adjacent the outlet end of the tank with the inner ends of the weir boxes spaced from the inlet end of the tank. The skimming apparatus is designed to remove all of the scum and floating matter from the entire tank, including the area where the weir boxes are located.

The skimming apparatus consists of an elongated blade that has spaced recesses or cutouts extending from the lower edge, the cutouts being transversely spaced on the blade and longitudinally aligned with the respective weir box. The spaced cutouts allow the lower edge of the blade to be below the liquid level in the weir area of the tank.

According to the invention, the skimming apparatus also includes power means for raising and lowering the blade on the bridge and the power means define a first skimming position for the blade where the lower end of the blade is located below the liquid level and the bases of the recesses are above the liquid level while the bridge is traveling in the skimming direction in the weir box area of the tank. The power means also define a second skimming position for the blade where the recesses and the lower edge of the blade are located below the liquid level while the blade is moving in the skimming direction in the area of the tank, between the weir boxes and the inlet. The power means define an inoperative position where the entire blade is above the liquid level when the bridge is traveling in the opposite direction.

In one embodiment of the invention, the power means consists of fluid ram means between the blade and the bridge with a control valve for supplying fluid to opposite ends of the ram means. In this embodiment, the control valve is actuated by switch means which are automatically actuated at selected locations along the bridge travel to supply the necessary amount of fluid to the ram means and move the blade between positions.

In an alternate embodiment, the power mean consists of a drum on the bridge with cable means on the drum and connected to the blade. A reversible drive motor is connected to the drum means for reeling and unreeling the cable means to again move the blade between the plurality of positions. In this embodiment, the reversible drive means can again be actuated by suitable switches carried on the bridge and actuated at selected locations along the bridge travel.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF DRAWINGS FIG. 1 is a fragmentary section showing a tank having the present invention incorporated therein;

FIG. 2 is an enlarged fragmentary transverse section of the tank of FIG. 1 showing the skimming apparatus in a first skimming position;

FIG. 3 is a view similar to FIG. 2 showing the skimming apparatus in the second skimming position; and

FIG. 4 is a fragmentary side elevation view of a slightly modified form of the invention.

DETAILED DESCRIPTION While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail several embodiments, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated.

FIG. 1 of the drawings shows liquid clarification tank 10 that has side walls 12 (only one being shown), inlet end 14, outlet end 16 and bottom wall 18. The inlet end 14 has inlet 20 for supplying mixed liquor, consisting of liquid having entrained or suspended solids therein, to the tank. The mixed liquor flows towards the outlet end 16, during which time the solids either settle to the bottom or floor of the tank or will float to the upper surface of the liquid. The outlet end 16 has an outlet 22 that is connected to a plurality of transversely spaced longitudinally extending weir boxes 24 that communicate with outlet 22 through openings 26 in outlet end 16. The weir boxes have bottom walls 24a and side walls 27 and weir boxes are opened at the top with the upper edges 28 of side walls 27 (FIG. 2) defining the liquid level for the tank.

In order to prevent floating matter from entering the open top weir boxes, baffles 30 surround the weir boxes and have upper and lower edges respectively located above and below the upper edges 28 of side walls 27. The baffles are supported through support brackets 32.

The solids that settle to the bottom of the tank by gravity as well as the scum, consisting of solids and other floating matter on the surface 34 of the liquid, are collected through the traveling bridge 40 that is supported on opposite sides ofthe tank through wheels 42 riding on rails 44 that extend along the respective side walls 12. The traveling bridge is reciprocated between extreme positions at the inlet and outlet ends of the tank through suitable drive means, such as a reversible motor (not shown).

The settled solids that are deposited on the floor or bottom 18 of the tank are removed through settled solids collecting means 46 that are supported on the bridge. The material collected by the settled solids collecting means 46 is delivered to a trough 48 extending along the bridge for removal to a suitable location (not shown). Since the settled solids collection means form no part of the present invention, a detailed description thereof does not appear to be necessary.

The traveling bridge 40 also supports skimming apparatus 50 for removing all of the scum that floats to the surface 34 of the liquid. The skimming apparatus 50 delivers the scum to a scum collection trough 52 located adjacent the inlet 20. Scum collection trough 52 consists of an elongated tube that has an opening adjacent the top and is supported on the sides of the tank for rotation about its own axis through suitable automatic or manual rotating means 54. In lieu of the rotating trough, a fixed trough or vessel with an inclined ramp could be used.

According to the present invention, skimming apparatus 50 is designed to remove floating matter from the surface 34 of liquid in the tank. The skimming apparatus 50 incorporates an elongated skimming blade 60 that is similar to the blade disclosed in the above mentioned co-pending application, portions of which are not inconsistent with the present disclosure being incorporated herein by reference. The elongated skimming blade 60 extends between opposite side walls 12 of the tank and is supported on the bridge through a plurality of arms 62 that are pivotally supported on pins 64 and have the blade fixedly secured to the opposite ends. The skimming blade 60 has a plurality of spaced cutouts or recesses 66 that are respectively longitudinally aligned with the longitudinally extending weir boxes at the outlet end of the tank.

The skimming apparatus further includes power means for pivoting the blade between extreme positions and also maintaining the blade in an intermediate position that will be described later. The power means consists of fluid or hydraulic ram means 70 (FIG. 2) interposed between the bridge 40 and the blade 60. I-Iydraulic fluid is supplied to opposite ends of cylinder 72 of the ram means 70 through a control valve 74 connected to opposite ends of the cylinder 72 through conduits 76. Control valve 74 is preferably a solenoid operated valve which is actuated by switch means 78 carried on the bridge. The switch means or switch 78 has an actuating arm 80 depending therefrom and a plurality of actuating means 82, 84 and 86 (FIG. 1) are positioned at spaced locations along tank side wall 12 and located in the path of actuating arm 80.

In operation, with the bridge traveling to the left as viewed in FIG. 1 and in the solid line position, the power means '70 will be actuated when switch arm 80 engages actuating member or stop 86 to move the skimming blade 60 from the solid line position to a raised position wherein the entire blade is located above the level of the liquid in the tank. The direction of bridge travel is simultaneously reversed and the bridge is moved toward the outlet end of the tank while the skimming blade is in the raised or inoperative position.

When the bridge reaches the opposite extreme position at the outlet end of the tank, switch 78 will again be actuated by actuating member 82 and valve 74 will supply a sufficient amount of fluid to cylinder 72 to move the blade 60 to the dotted line position shown at the right hand portion of FIG. 1 and in the solid line in FIG. 2. In this position, the bases of the recesses 64 are located above edges 28 as well as the upper edges of the baffles 30, while the lower edge of the skimming blade 60 is located below the liquid level 34 in the tank. Thus, in this position, which is termed a first skimming position for the blade, the lower edge of the blade is lo cated below the liquid level while the bases of the recesses are above the liquid level and the bridge is traveling towards the inlet end 14 in the weir box area of the tank to remove all of the scum from the surface of the liquid between the weir boxes. When the traveling bridge 40 reaches an intermediate position adjacent the opposite or inner ends ofthe weir boxes, switch 78 will again be actuated by actuating member 84 to cause the valve again to be actuated and lower the blade from the position shown in the right hand portion of FIG. 1 to that shown in the left hand portion of FIG. 1. This second skimming position for the blade will place the bases of the recesses and the lower edge of the blade below the liquid level 34 during the period of time where the blade is traveling between the ends of the weir boxes and the inlet end of the tank.

A slightly modified form of the invention is shown if FIG. 4, wherein the traveling bridge 40 and skimming blade 60 as well as the support 62 are identical in construction. In this embodiment, the hydraulic power means is replaced with a plurality of spaced drums or drum means 90 each having one end of a cable 92 connected thereto, the opposite end of which is connected to the blade. The drums 90 are fixed to a shaft 94 that is rotated on the bridge through a reversible drive motor 96.

The modified embodiment operates in the same manner as the previously described embodiment and the actuating switch 78 operates the reversible motor 96 at the proper time to move the skimming blade between the three positions described above.

As can be seen from the above description, both embodiments of the invention provide a simple and inexpensive mechanism for positively holding the skimming blade in any one of a plurality of positions without any direct contact between the movable blade and any fixed portions of the tank.

Numerous modifications of either embodiment come to mind without departing from the spirit of the invention. For example, both embodiments show the blade as beingpivoted by support arms 62, the blade could readily be supported directly through the fluid rams or the cable means with or without positive guide means for producing vertical reciprocal movement of the blade relative to the bridge. Also, one or more fluid rams or drums could be used to support the blade in the various pivoted positions.

In addition, the motive power for the blade could be provided with other types of power means such as an electric ram, a chain and sprocket arrangement or a fluid motor.

It should also be noted that while the skimming apparatus has been shown as being operative to move the scum from the outlet towards the inlet of the tank, the blade could readily be operated in the reverse direction with the trough located at the outlet or it could be operative in both directions with troughs located at both ends.

I claim:

1. In a liquid clarification apparatus including a tank having an inlet for supplying fluid with entrained solids and an outlet for receiving clarified liquid, said outlet including a plurality of transversely spaced longitudinally extending weir boxes, said weir boxes each having a bottom wall and side walls having upper edges defining the liquid level for said tank; baffle structure surrounding each weir box, said baffle structure having upper and lower edges respectively located above and below said upper edges; a traveling bridge above said tank; drive means for reciprocating said bridge between extreme positions parallel to said longitudinally extending weir boxes; and skimming means depending from said bridge for removing scum from the surface of said liquid, said skimming means including an elongated blade extending transversely of said tank, said blade having recesses aligned with said weir boxes and extending from the lower edge of said blade, said recesses allowing the lower edge of the blade to be below the liquid level while the bridge is in the weir box area of the tank; power means for raising and lowering said blade on said bridge, said power means defining a first skimming position for said blade where the lower edge of the blade is located below the liquid level and the bases of the recesses are above said upper edges of said side walls when said bridge is traveling in one direction in the weir box area of the tank, said power means defining a second skimming position for Said blade wherein the recesses and the lower edge of said blade are located below said upper edges of said side walls while the blade is located in the area of the tank between the weir boxes and the inlet end, said power means defining a third inoperative position for said blade where the lower edge of said blade is located above said upper edges of said side wall; said power means including fluid rams between said blade and said bridge, valve means connected to said fluid rams; switch means cooperating with said valve means and carried by said bridge; and actuating means for actuating said switch means when said bridge is at opposite ends of said tank and at inner ends of said weir boxes to operate said valve means and move said blade between said positions.

2. In a liquid clarification apparatus including a tank having an inlet for supplying fluid with entrained solids and an outlet for receiving clarified liquid, said outlet including a plurality of transversely spaced longitudinally extending weir boxes, said weir boxes each having a bottom wall and side walls having upper edges defining the liquid level for said tank; baffle structure surrounding each weir box, said baffle structure having upper and lower edges respectively located above and below said upper edges; a traveling bridge above said tank; drive means for reciprocating said bridge between extreme positions parallel to said longitudinally extending weir boxes; and skimming means depending from said bridge for removing scum from the surface of said liquid, said skimming means including an elongated blade extending transversely of said tank, said blade having recesses aligned with said weir boxes and extending from the lower edge of said blade, said recesses allowing the lower edge of the blade to be below the liquid level while the bridge is in the weir box area of the tank; power means for raising and lowering said blade on said bridge, said power means defining a first skimming position for said blade where the lower edge of the blade is located below the liquid level and the bases of the recesses are above said upper edges of said side walls when said bridge is traveling in one direction in the weir box area of the tank, said power means defining a second skimming position for said blade wherein the recesses and the lower edge of said blade are located below said upper edges of said side walls while the blade is located in the area of the tank between the weir boxes and the inlet end, said power means defining a third inoperative position for said blade where the lower edge of said blade is located above said upper edges of said side wall; said power means including a shaft rotatable on said bridge, drum means fixed to said shaft, cable means between said drum means and said blade, reversible drive means connected to said shaft; switch means cooperating with said drive means and carried by said bridge; and actuating means for actuating said switch means when said bridge is at opposite ends of said tank and at inner ends of said weir boxes to operate said drive means and move said blade between said positions.