GB2129697A - Surface skimming device - Google Patents

Abstract

A surface skimming device includes a sealed tank (11) pivotally mounted at (15) and having a filling pipe (14) which can be above, at, or below, the liquid surface in dependence upon the pivotal position of the tank. Foam or light liquid can be skimmed from the surface of heavier liquid by a pump connected through a flexible pipe (18). If the pump demand exceeds the flow into pipe (14) from the surface, liquid is drawn from tank (11) causing it to rise and thus dipping pipe (14) below the surface. As shown the device is pivoted to a float (17), but it can be pivoted to the wall of an enclosing vessel. <IMAGE>

Description

SPECIFICATION Surface skimming device This invention relates to a surface skimming device for skimming from the surface of a liquid floating foam or solids on a lighter liquid phase. Such a device can be usedforskimming offtramp oils from coolant systems and industrial washing machines, and oil spills from sumps.

Various skimming devices have been proposed in which a pipe is supported by floats, with the entry nozzle being at aboutthe surface ofthe liquid, but with some ofthose devices a pump for extracting the liquid can run dry if the nozzle isabovethesurfaceofthe liquid, perhaps due to the surface being turbulent, and in any case it is difficult to extract floating solids and foam. Some other prior devices do not operate well if the level of liquid can varysubstantially.

According to the present invention a surface skimming device comprises a pivotally mounted tank having a filling pipe leading to itfrom a nozzle or opening which will be above, at, or below, the liquid surface in dependence upon the pivotal position of the tank.

The arrangement can be designed so that as more liquid is drawn off, the device pivots to lowerthe nozzle below the liquid surfacesothatthere is always adequate liquid to prevent the pump from running dry. Then as liquid continues to be drawn off, the balance can be automatically readjusted until the nozzle is just above the liquid surface, so that automatic compensation for any variation in the rate of entry of liquid through the nozzle to the pump demand is achieved. Also the lowering of the nozzle belowtheliquidsurfaceenablesfoam andfloating solidsto be drawn throughthe nozzle asthe liquid enters.

Thetankwill generally be a sealed tank with a larger volumethan thefiiling pipe, sothat liquid being drawn offwill be preferentially taken from the tank until the free space in the tank is at reduced pressure when most of the liquid will be taken from the filling pipe.

An exit from the device to a pump is conveniently nearwherethe filling pipe joins the tank near the bottom ofthetank, and the exit may be byway of a flexible pipe.

The space above the liquid level in the tank may contain a damping pipe terminating part-way down thetank by having an adjustable airvalvesothat nodding movement ofthe device between its positions of which the nozzle is above and below the liquid surface can be damped, the degree of damping being capable of being set by adjusting the valve to setthe rate at which aircanflowthrough it.

In a preferred form oftheinvention,the pivotforthe tank is carried by one or more floats so that the device is independent of the level of liquid in the container. In anotherembodimentthe pivot is carried by a pairof horizontally spaced arms which are themselves pivoted from the wall ofthe container orfrom some other structure about a horizontal axis so thatthe device can set itself in accordance with the liquid level.

In another embodiment in which the liquid level. In another embodiment in which the liquid level is more-or-less fixed, the pivot axis can itself be fixed to some structure ofthe container.

The invention may be carried into various ways, and two embodiments will now be described by way of example, with reference to the accompanying drawings, in which FIGURES 1 and3aresideelevationsofthe skimming device in two pivotal positions of adjustment; FIGURE 2 is a plan view of FIGURE 1 and FIGURES 4 and 5 are on an elevation and plan of another form of skimming device.

The device comprises a sealed tank 11 having an opening 12 nearthe bottom connected through a pipe 13tothe nozzle 14forcollection of a surface liquid. The tank 11 is pivotally mounted at 15 on a horizontal bar and in the embodiments of FIGURES 1,2 and 3, that bar is supported a little above the surface ofthe liquid bya pair of horizontally spaced floats 17.

There is an exit from the pipe 13 atthe bottom near where it opens into the tank 11, and that leads by way of a flexible conduit 18to an extractor pump (not shown).

An air damping pipe 19 is sealed into the top ofthe tank 11 and projects about halfway intothetankwhile it is fitted with an adjustable needle valve 21 outside the tank.

If as shown in FIGURE 1, the liquid level in thetank and the pipe is about half way up the tank and pipe, then the unit will set itself aboutthe pivot 15 to be balanced with the nozzle 14 just above the surface level. In thatsettingthe lower end of the airdamping pipe 19 is just not covered bythe liquid inthetank 11, sothatthe pressure within thetank is equal to atmospheric pressurewhilethevalve 21 isopen. The valve is then closed.

During operation when the pump is started, liquid is drawn from the tank and pipe with most of it being taken from the tankwhich is the largestvolume, so thatthe tanktends to float higher in the liquid, and the device pivots in a clockwise direction about the axis 15 until the nozzle 14 drops belowthesurface of the liquid as shown in FIGURE 3.

Liquid enters the pipe 13 and such of that liquid as is not required to supportthe pump demand enters into the tankthrough the opening 12 so as gradually to increase ite weight, and so that the device pivots back in an anti-clockwise direction until the nozzle 14 is then abovethe surface of the liquid.

Thus, the nozzle continually seeks the liquid surface with a kind of nodding action, and that action is damped bythetrapped air space in the top of the tank 11 which expands as the internal liquid level drops, so that as the pressure in that space falls, more of the pump demand is met through the pipe 13 and nozzle 14, and the rate at which the level in the tank 11 falls is reduced. When the nozzle 14 is belowthe surface and the level in the tank 11 is rising, the space above it will be progressively compressed by the incoming liquid The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

so that more ofthe pump flow is taken from the tank, and less from the nozzle until that equals the pump demand.

The damping action can be set by adjusting the needle valve 21 from being fully closed, through allowing a trickle of airto pass, to being fully opened.

The pump cannot run dry because if the pump demand is not sufficient, the device pivots to lower the nozzle 14 belowthe liquid level.

This also hasthe advantage thatfloating solids and foam which cannot easily be removed by a device having a nozzle permanently at the surface of the liquid can be quite readily extracted as the nozzle is lowered in the FIGURE 3 position, and liquid will enter the nozzle drawing in solids and foam.

In the embodiment shown in FIGURE 4,the tank, nozzle, valve, and pump, connection are the same, but instead of being pivoted on a rod carried by floats, pivoting is on a rod 15 which extends horizontally between a horizontally-spaced pair of generally horizontal arms 23 which are themselves mounted about horizontal-pivots in thewall ofthetankasshown in 24.

The end ofthe pipe 18 is secured in a fitting above the pivots 24.

Operation is similar, but it will be noticed thatthe tank 11 acts as a float causing the complete pivoting device to go up or down with the level of liquid in addition to acting to control pivoting aboutthe axis 15 in acccordance with the relationship between the pump demand and the flow from the surface through the nozzle 14. With that arrangementthe liquid level can vary a little. In a system in which the liquid level wassubstantiallyconstant,thehorizontal bar 15 could itself be fixed. The advantage of the arrangement of FIGURES 1,2 and 3 isthatthe unit is free to travel over thesurface ofthe liquid being constrained only by the flexible hose 18.

The device could be used without a suction pump if the flexible pipe 18 was taken to a level belowthe level in the device, so that liquid could be drawn off by gravity.

CLAIMS (Filed on 11 Nov. 1983) 1. A surface skimming device comprising a pivotally mounted tank having a filling pipe leading to it from a nozzle which will be above, at, or below, the liquid surface in dependence upon the pivotal position ofthe tank 2. Adevice as claimed in Claim 1 in which thetank is a sealed tank with a largervolumethanthefilling pipe.

3. A device as claimed ineitherofthe preceding claims in which an exitfrom the devicefor connection to a pump is near where the filling pipe joins the tank.

4. Adeviceascaimed in any of the preceding claims in which the filling pipe joins the tank near the bottom ofthetank.

5. A device as claimed in any of Claims 3 or Claim 4 in which the exit constitutes a flexible pipe.

6. A device as claimed in any ofthe preceding claims in which the space at the top of the tank contains a damping pipeterminating part-way down the tank.

7. A device as claimed in Claim 6 in which the damping pipe includes an adjustable air valve.

8. Adevice as claimed in anyofthe preceding claims in which a pivotforthetank is carried by a float.

9. A device as claimed in any of Claims 1-7 in which a pivotforthetank is carried by at least one generally horizontal arm secured to a wall of the container for fluid whose surface is to be skimmed.

10. A device as claimed in Claim 9 in which the generally horizontal arm is pivotally mounted about a horizontal axis.

11. A device as claimed in Claim 9 in which the pivot axis is fixed in relation to the wall of the container.

12. A surface skimming device constructed an arranged substantially as herein specifically described with reference to FIGURES 1-3, or4 and 5, ofthe accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. so that more ofthe pump flow is taken from the tank, and less from the nozzle until that equals the pump demand. The damping action can be set by adjusting the needle valve 21 from being fully closed, through allowing a trickle of airto pass, to being fully opened. The pump cannot run dry because if the pump demand is not sufficient, the device pivots to lower the nozzle 14 belowthe liquid level. This also hasthe advantage thatfloating solids and foam which cannot easily be removed by a device having a nozzle permanently at the surface of the liquid can be quite readily extracted as the nozzle is lowered in the FIGURE 3 position, and liquid will enter the nozzle drawing in solids and foam. In the embodiment shown in FIGURE 4,the tank, nozzle, valve, and pump, connection are the same, but instead of being pivoted on a rod carried by floats, pivoting is on a rod 15 which extends horizontally between a horizontally-spaced pair of generally horizontal arms 23 which are themselves mounted about horizontal-pivots in thewall ofthetankasshown in 24. The end ofthe pipe 18 is secured in a fitting above the pivots 24. Operation is similar, but it will be noticed thatthe tank 11 acts as a float causing the complete pivoting device to go up or down with the level of liquid in addition to acting to control pivoting aboutthe axis 15 in acccordance with the relationship between the pump demand and the flow from the surface through the nozzle 14. With that arrangementthe liquid level can vary a little. In a system in which the liquid level wassubstantiallyconstant,thehorizontal bar 15 could itself be fixed. The advantage of the arrangement of FIGURES 1,2 and 3 isthatthe unit is free to travel over thesurface ofthe liquid being constrained only by the flexible hose 18. The device could be used without a suction pump if the flexible pipe 18 was taken to a level belowthe level in the device, so that liquid could be drawn off by gravity. CLAIMS (Filed on 11 Nov. 1983)

1. A surface skimming device comprising a pivotally mounted tank having a filling pipe leading to it from a nozzle which will be above, at, or below, the liquid surface in dependence upon the pivotal position ofthe tank

2. Adevice as claimed in Claim 1 in which thetank is a sealed tank with a largervolumethanthefilling pipe.

3. A device as claimed ineitherofthe preceding claims in which an exitfrom the devicefor connection to a pump is near where the filling pipe joins the tank.

4. Adeviceascaimed in any of the preceding claims in which the filling pipe joins the tank near the bottom ofthetank.

5. A device as claimed in any of Claims 3 or Claim 4 in which the exit constitutes a flexible pipe.

6. A device as claimed in any ofthe preceding claims in which the space at the top of the tank contains a damping pipeterminating part-way down the tank.

7. A device as claimed in Claim 6 in which the damping pipe includes an adjustable air valve.

8. Adevice as claimed in anyofthe preceding claims in which a pivotforthetank is carried by a float.

9. A device as claimed in any of Claims 1-7 in which a pivotforthetank is carried by at least one generally horizontal arm secured to a wall of the container for fluid whose surface is to be skimmed.

10. A device as claimed in Claim 9 in which the generally horizontal arm is pivotally mounted about a horizontal axis.

11. A device as claimed in Claim 9 in which the pivot axis is fixed in relation to the wall of the container.

12. A surface skimming device constructed an arranged substantially as herein specifically described with reference to FIGURES 1-3, or4 and 5, ofthe accompanying drawings.