BACKGROUND ART This invention comprises improvements in the oil skimmers disclosed in United States Patent No. 3,715,034, Issued: Feb- ruary 6,1973 to A. Ivanoff entitled DEVICE FOR REMOVING OIL SLICKS and United States Patent No. 5,194,164, Issued: March 16, 1993 to George W. Adams. According to the above-identified Ivanoff patent"oil floating on a body of water is collected by moving a shallow-draft water craft, such as a barge, having a sternwardly slanted bow section and below the water line an in- gress opening in or near the bow section through an oil slick.

The slant of the bow section forces oil in its path downwardly thereby causing the oil, possibly intermingled with water, to flow as a flat layer along the bottom of the barge. As the oil reaches the ingress opening it is propelled into a hold of the barge due to the pressure differential between the outside and the inside of the barge. Oil thus accumulating in a hold of the barge may be removed therefrom from time to time and clear water as may also enter the hold is returned to the body of water." The effectiveness of skimmers, according to the above-iden- tified patent, decreases as the velocity between the skimmer and the water surface increases. This is due to the bow wave created by the inclined-plane which tends to collect oil in front of the bow wave and to reduce the velocity of the oil relative to the surface of the inclined-plane to the point where the oil does not go down it for collection.

I discovered that by positioning a transverse body ahead of the bow, water surface interface and below the surface of the water a surface wave may be created which is out of phase with the surface wave created by the inclined-plane and destructively interferes with it. This body can also increase the fluid veloc- ity at the forward surface of the inclined-plane. The simplest body that produces these results is a cylinder, the axis of which is generally parallel to the water surface, bow interface. A better form is a foil-lifting body. The foil-lifting body may be extended rearwardly toward the water surface, bow interface and may be extended upwardly in winglets at the outer edges thereof.

The winglets also extend inwardly to guide oil to the inclined- plane which would otherwise be pushed aside by the bow wave.

This improvement which I call the hydrodynamic induction bow foil is disclosed in the above-identified United States Patent No.

5,194,164.

Such a submersion plane skimmer employing my hydrodynamic induction bow foil is shown in Figures 1 through 3 and is manu- factured by Webster Barnes, Inc. of 18 McKinley Street, Roway- ton, Connecticut 06853.

As shown in Figures 1 through 3, the body of the skimmer 20 is a barge-like shape with an inclined submersion plane 22 at the bow 24. The separation tank 26 in the center of skimmer 20 has two horizontal layers of baffles or separation decks 28,30 and is open to the sea through a perforated bottom 32. At the forward end of the separation tank 26 is a collection basin or hold 28 where a discharge pump 34 is located. The skimmer body 20 is supported on each side by pontoons 36,38 which are detachable for transport. As the skimmer 20 advances, oil 40 and surface water 42 are gently deflected downward by the hydrodynamic induction bow foil 44. The mixture descends along the submersion plane 22 to a scoop 46 that directs the oil, and a thin layer of water, into the separation tank 26. As the mixture slows down, the oil floats upward and the water flows downward and out through the perforated bottom 32. A weak flow at the surface of the separa- tion tank moves the separated oil forward over floating weir 48 to the collection basin 28 and discharge pump (not shown).

Several problems have been encountered in operating the skimmer 20. The hydrodynamic induction bow foil ideally should remain at a preset distance below the surface to maximize the reduction in the bow wave. However, trim of the skimmer 20 was found to change, going bow down with increasing collection speed.

The skimmer 20 tends to pitch in rough water. These effects increased turbulence at the inlet scoop 46 reducing collection efficiency.

Some turbulence was noted starting between the trailing edge of the foil 44 and the nearest portion of the submersion plane 22 and some was induced at high collection speeds by the foil 44 itself.

Additional turbulence was induced at the inlet 49 between the scoop 46 and the bottom of the submersion plane 22.

The placement of a pump over the collection basin 28 was awkward because of the self-adjusting weir 48. When placed over the collection basin 28 or, even worse, on the forward deck 51, the added weight and high center of mass increased the previously mentioned bow down trim effect.

Ideally, the oil slick should move smoothly down the submer- sion plane, through the inlet 48, and into the separation tank 26 without any induced turbulence.

DISCLOSURE OF THE INVENTION I have discovered that greatly improved non-turbulent flow may be achieved by: transitioning the bottom of the submersion plane, when viewed from below, in convex, then concave, and then in substantially horizontal portions; forming the curvature of the scoop to be substantially coaxial with said convex portion; hinging the aft end of said scoop so that said opening may be varied by selectively positioning said scoop; cambering the foil; making the trailing upper surface of the foil substan- tially parallel to the submersion plane; using hull-like pontoons that narrow from about the waterline to the bottom thereof; locating the collection basin or hold substantially over the opening at the bottom of the submersion plane; locating the pump substantially over the opening at the bottom of the submersion plane; and locating said pump as aft as possible by placing a pair of weirs at either side of said pump.

Additionally, I have found that by extending the one of the sides of the hull-like pontoons forward and placing fastening means therein, a one of variety of differing boom connectors may be fastened thereto, as needed.

OBJECTS OF THE INVENTION It is therefore an object of the invention to improve in- clined-plane oil skimmers.

Another object of the invention is to increase the velocity with which such oil skimmers may operate effectively.

A further object of the invention is to decrease turbulence in the collection of an oil slick by such skimmers.

More specific objects of the invention are: to decrease turbulence caused by a hydrodynamic induction bow foil in such a skimmer; to decrease turbulence caused by the presence of said bow foil adjacent the inclined plane; to decrease turbulence induced at the inlet of an oil slick into such skimmer; to de- crease turbulence caused by velocity dependent trim effects; and to decrease turbulence caused by wave induced pitching of such skimmers.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of con- struction, combinations of elements, and arrangements of parts which will be exemplified in the constructions hereinafter set forth.

The scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings, in which: FIGURE 1 is a perspective view of an oil skimmer according to the prior art lashed to a tender therefore; FIGURE 2 is a diagrammatic top view of the prior art skimmer of Figure 1; FIGURE 3 is a diagrammatic side view of the prior art skimmer of Figure 1; FIGURE 4 is a perspective view of a hydrodynamic induction bow foil submersion plane oil skimmer according to my present invention; FIGURE 5 is a diagrammatic plan view of the skimmer of Figure 4; FIGURE 6,7, and 8 are diagrammatic side views of the skimmer of Figure 5; FIGURE 9,10, and 11 are diagrammatic side views of the separation decks and bottom of the oil skimmer of Figure 4; FIGURE 12 is a diagrammatic cross-sectional view, partially cut away, takes along the line 12-12 of Figure 7; FIGURE 13 is a diagrammatic side view, partially cut away, of the bow of one of the pontoons of the skimmer of Figure 4;; FIGURE 14 is a cross sectional view taken along the line 14-14 of Figure 13; FIGURE 15 is a cross-sectional view similar to Figure 14 showing how differing boom connectors may be affixed to the skimmer of Figure 4; FIGURE 16 is a diagrammatic cross-sectional view, partially cut away, showing how the scoop opening may be varied; and FIGURES 17 and 18 are preferred embodiments of the invention similar to Figure 8.

BEST MODE FOR CARRYING OUT THE INVENTION Now referring to Figure 4, a hydrodynamic induction bow foil submersion plane skimmer 50, according to my present invention, comprises a pair of hull-like pontoons 52,54 terminating in upper deck-like portions 56,58. Stern portion 60 may also be a sealed air compartment terminating at deck-like portion 62.

The pontoons 52,54 terminate at narrowed bow portions 64,66.

The forward bow portions of pontoon decks 56 and 58 are nearly planner with a bow deck 68 which is slightly inclined from bow to aft over an inclined submersion plane 70 (see Figure 6).

Attachment means 72,74,76, and 78 are provided for launching and removing the skimmer 50 from the water.

The upper separation deck or baffles 80 may be seen in Fig- ure 1. Oil comes up through the slot-like openings 82 therein during skimming operations. The oil, on top of any water that may have been collected flows forward over floating weirs 84 and 86 (only one of which is shown in Figure 4) into a small oil col- lection tank or hold 88.

A pump (not shown in Figure 4) may be located within and above the center of the collection tank for removing the oil therefrom to a work boat with the skimmer 50 in tow.

An arm 90 is provided for adjusting the scoop (not shown in Figure 4).

Now referring to Figures 5,6, and 7, the skimmer may be fitted with a bumper rail 92 about the upper periphery thereof.

The pump 94 (as best seen in Figure 5) is centered in the oil collection hold 88 on chair-like stand 89 (see Figure 8).

The weirs 86,88 are hinged at 96,98 at the bow end of separation deck 80. They are provided with floatation means 100,102 at their top edges.

The hydrodynamic induction bow foil 104 is located under the inclined submersion bow plane 70. It is preferable aft cambered with the trailing upper surface 106 thereof nearly parallel to the plane 70.

Plane 70, as seen from the bottom, terminates in a convex portion 108 then a concave portion 110 and then a plane hori- zontal portion 112. A plane portion 114 is located between con- vex portion 108 and concave portion 110.

The oil collecting hold 88 and pump 94 are located over the concave portion 108 terminating the immersion plane 70 with the center of mass of the oil and pump being slightly aft of concave portion 108.

In Figure 8, it can be seen how the immersion plane smoothly transitions from planar to convex (to planar), to concave and to planar, inline with the bottom of separation deck 116. The flow is further guided by scoop 118 which is hinged to the bottom 120.

The scoop 118 may be adjusted to several positions as dis- cussed below.

Frame members 122 support the immersion plane 70 and the deck 68.

The forward wall 122 and rear wall 124 of the oil collection hold 88 are shown in Figure 7.

Its"S"shaped bottom is generally indicated at 126 and structural ribs at 128. The corners 130,132 may be seen in Fig- ures 5 and 8.

Figures 9,10, and 11 show the upper and lower separation decks 80,116 and the bottom 120, respectively. Each is perfo- rated by transverse channels indicated at 134 in deck 80,136 in deck 116, and 138 in bottom 120. Note that these vary in size and are offset from each other in decks 80 and 116 and bottom 120.

Figure 12 is a partial representative cross-section showing the pontoon 52; decks 80,116 and bottom 120. The pontoon 52 comprises a vertical side wall 140 inside the skimmer to which are mounted decks 80,116 and bottom 120. Outer upper vertical wall 142 terminates at its lower edge 144 at about the water line. Lower diagonal wall 146 terminates at straight bottom section 148.

Various cross members (not shown) are used to strengthen the pontoon 52. Pontoon 54 is the mirror image of pontoon 52.

Vertical inner side wall 140 of forward pontoon 64 is ex- tended forward at 152 in front of skimmer 50 (see Figures 13-15 and 6). Diagonal side wall 154 is welded to wall 140 as shown.

Extended portion 152 has holes 155 therein for receiving bolts 156 for affixing differing boom connectors 158 and 160 thereto when booms are deployed as shown in Figure 1.

Now referring to Figure 16, scoop 118 is hinged to bottom 120 at hinge 162. Adjusting arm 90 is"L"shaped and rotates about pivot 164. Link 166 is pivoted to arm 90 and scoop 188.

Holes 168 in arm 90 cooperate with holes 170 and a removable bolt (not shown) to allow positioning scoop 118 in one of a variety of positions as required by the nature of the oil spill and speed of collection.

One of several debris exclusion bars 168 can also be seen in Figure 16.

I have tested a cambered foil 104 which was a NACA 5617 and it reduced turbulence due to the foil itself significantly over my uncambered prior art foils. Placing the trailing surface of the foil substantially parallel to the immersion plane 70, re- duced turbulence induced along the plane 70 due to the presence of the foil 104. However, I believe a thinner cambered foil such as NACA 5612 would further reduce turbulence due to the foil itself. NACA 5617 has a thickness to cord ratio of 17% while NACA 5612 has a thickness to cord ratio of 12%. Both of these foils have their point of maximum camber behind the center of their cord and reduce sensitivity to angle of attack.

I have discovered that the point of maximum camber of the foil should be from about. 5 to about. 85 of the cord rearward of the leading edge. More preferably in the range of about. 6 to about. 75.

The thickness to cord ratio of the foil should be less than about 17%. The optimum range is about 8% to about 12%, but from about 6% to about 15% will work.

The foil should have a high camber ratio, higher than about. 05 and may range up to about. 15. The preferred range is from about. 08 to about. 12.

I have found a NACA 9612 foil having a camber ratio of. 09 to work better than lower ratio foils and even higher camber ratios are better. The foil has a point of maximum camber of. 6 and a thickness to cord ratio of 12%.

Now referring to FIGURE 17, the foil 200 preferably is as big as possible for skimmer up to about 40 meters in length. Thus, the leading edge 202 should be as far forward as possible within the protraction of the pontoons 52 and 54. The trailing edge should extend as far aft as possible, limited by the size of opening between it and the bow surface 70. This reduces the tendency to stall under varying flow conditions.

Because the skimmer tends to go stern down at high speeds, I provide additional buoyancy aft in the air tanks indicated at 206. These preferably extend the breath of the transom. They are located above the static water surface 208. Underway, the external aft tank 210 resists upward bow by going under water aft.

Internal tank 212 reduces the amount of oil and water than can flow aft in the separator indicated at 214. This reduces the amount the center of gravity would otherwise move aft due to additional oil and water in the aft portion of the separator above the static water surface.

Now referring to FIGURE 18, I have found that the plane horizontal portion 112 should extend further aft under the upper baffle deck 80. Portion 112 extends into middle baffle deck 116 at 214. Portion's 112 length should be between about 4 to about 6 times the distance between decks 116 and 120. Extension 214 ends in a forward porous portion 215 of deck 216 that is less porous than the aft portion 217.

The upper baffle deck 80 is also less porous forward than aft, but less porous than middle deck 116.

Lower baffle deck 120 is closed off at 121 under substantially all of the more porous portions of upper decks 80 and 116.

The extended throat 216 smooths the flow between the lower and middle decks and the aft portion of the bottom deck 120 is made more porous to aid this flow, as is the aft portion of the middle baffle deck 116. The forward flow of oil above deck 80 is thus increased and less turbulent. The return flow between decks 80 and 116 is also increased and less turbulent.

Each of the above described features add to the efficiency and speed of collection. All but the multiple boom connectors comparatively decrease the turbulence of the flow of oil and water into the skimmer to minimize mixing of oil and water and allowing the oil slick to flow smoothly under the middle collection or baffle deck 116.

More specifically, the taper of the pontoons below the waterline reduces pitching and variation in trim due to speed. Placement of the oil collection hold and pump over the inlet and low down also reduces pitching and trim variation due to speed. Use of a rear cambered foil (one with the maximum camber behind the mid- point of the cord) allows fine adjustment of the angle of attack of the foil to minimize turbulence and greatly decreases turbulence caused by angle of attack variation due to pitching or skimmer trim variation. The smoothly varying terminating portion of immersion plane beginning below the bottom of lowest separation deck, initially convex, then concave, then planar with the bottom of the lowest separation deck and the coaxial shape of the scoop all direct the flow of the slick under the lowest separation deck with minimum turbulence. Having the near surface of the foil substantially parallel to the immersion plane minimizes the turbulence due to the interaction between the foil and the immersion plane. The adjustable scoop opening allows the amount of water taken into the skimmer to be minimized.

CLAIMS 1. In an oil skimmer comprising a hull for floating on a water surface and comprising a bow, a stern, and a hold within said hull for containing oil, said bow comprising an inclined surface extending from above said water surface downwardly and rearwardly through said water surface toward said stern and ter- minating in an opening into said skimmer, the improvement com- prising: said inclined surface when viewed from under the skim- mer substantially smoothly transitioning at said opening from said bow in substantially convex, then substantially concave, and then substantially horizon- tal portions; a foil lifting body under said water surface, ahead of said inclined surface, extending transverse to a center line of said skimmer drawn from bow to stern, and said foil lifting body being cambered ; a pair of hull-like pontoons forming the sides of said skimmer; said pontoons narrowing from about the water line to the bottom thereof; and said hold being located substantially above said opening; whereby smooth increased nonturbulent flow of oil and water into said skimmer is achieved.

2. The skimmer defined in claim 1 and a pump for pumping oil from said hold located substantially above said opening in said hold.

3. The skimmer defined in claim 1 and a pair of plates extending forward of said side walls comprising means for attaching one of a plurality of differing boom connectors thereto.

4. The oil skimmer defined in claim 1 and a pair of up- standing floating weirs at either side of the sternwise portion of said hold.

5. The oil skimmer defined in claim 1 and a pump for pumping oil from said hold located at least in part between said weirs.

6. The oil skimmer defined in claim 5 wherein said pump is substantially located above said opening.

7. The oil skimmer defined in claim 1 and a pump for pumping oil from said hold substantially located above said opening.

8. The oil skimmer defined in claim 7 wherein said pump is substantially located within said hold.

9. The oil skimmer defined in claim 1 wherein there is a straight portion between said concave and convex portions.

10. The oil skimmer defined in claim 1 and a separation deck and wherein said convex portion substantially smoothly tran- sitions the flow of oil and water along said inclined surface into the flow of oil and water into said separation deck.

11. The oil skimmer defined in claim 10 wherein said in- clined surface is substantially planner.

12. The oil skimmer defined in claim 1 wherein said in- clined surface is substantially planner.

13. The oil skimmer defined in claim 1 and a hinged bottom scoop located below said convex portion and means for positioning the forward edge thereof in a plurality of positions.

14. The oil skimmer defined in claim 1 wherein said hydro- foil is cambered.

15. The oil skimmer defined in claim 1 and a hydrofoil located in front of said inclined surface.

16. The oil skimmer defined in claim 15 wherein the trailing upper surface of said hydrofoil is generally parallel to the portion of said inclined surface closest thereto.

17. The oil skimmer defined in claim 15 wherein said hydro- foil is cambered.

18. The oil skimer defined in claim 1 wherein the trailing upper surface of said foil lifting body is generally parallel to the closest portion of said inclined surface.

19. In an oil skimmer comprising a hull for floating on a water surface and comprising a bow, a stern, oil and water sep- arating means, and a hold within said hull for containing oil, said bow comprising an inclined surface extending from above said water surface downwardly and rearwardly through said water sur- face toward said stern and terminating in an opening into said skimmer, the improvement comprising: said hold being located substantially above said opening.

20. The oil skimmer defined in claim 19 wherein: said inclined surface when viewed from under the skim- mer substantially smoothly transitioning at said opening from said bow in convex, then concave, and then substantially horizontal portions.

21. The oil skimmer defined in claim 20; and, a foil lifting body under said water surface, ahead of said inclined surface, extending transverse to a center line of said skimmer drawn from bow to stern, and said foil lifting body being cambered.

22. The oil skimmer defined in claim 21; and, a pair of hull-like pontoons forming the sides of said skimmer; said pontoons narrowing from about the water line to the bottom thereof.

23. The oil skimmer defined in claim 20; and, a pair of hull-like pontoons forming the sides of said skimmer; said pontoons narrowing from about the water line to the bottom thereof.

24. The oil skimmer defined in claim 19 ; and, a foil lifting body under said water surface, ahead of said inclined surface, extending transverse to a center line of said skimmer drawn from bow to stern, and said foil lifting body being cambered.

25. In an oil skimmer comprising a hull for floating on a water surface and comprising a bow, a stern, and a hold within said hull for containing oil, said bow comprising an inclined surface extending from above said water surface downwardly and rearwardly through said water surface toward said stern and ter- minating in an opening into said skimmer, the improvement com- prising: said inclined surface when viewed from under the skim- mer substantially smoothly transitioning at said opening from said bow in substantially convex, then substantially concave, and then substantially horizon- tal portions.

26. In an oil skimmer comprising a hull for floating on a water surface and comprising a bow, a stern, and a hold within said hull for containing oil, said bow comprising an inclined surface extending from above said water surface downwardly and rearwardly through said water surface toward said stern and ter- minating in an opening into said skimmer, the improvement com- prising: a foil lifting body under said water surface, ahead of said inclined surface, extending transverse to a center line of said skimmer drawn from bow to stern, and said foil lifting body being cambered.

27. In an oil skimmer comprising a hull for floating on a water surface and comprising a bow, a stern, and a hold within said hull for containing oil, said bow comprising an inclined surface extending from above said water surface downwardly and rearwardly through said water surface toward said stern and ter- minating in an opening into said skimmer, the improvement com- prising: a pair of hull-like pontoons forming the sides of said skimmer; said pontoons narrowing from above the water line to the bottom thereof.

28. In an oil skimmer comprising a hull for floating on a water surface and comprising a bow, a stern, and a hold within said hull for containing oil, said bow comprising an inclined surface extending from above said. water surface downwardly and rearwardly through said water surface toward said stern and ter- minating in an opening into said skimmer and a pair of generally verticle side walls extending above and below the water line, the improvement comprising: a pair of plates extending forward of said side walls comprising means for attaching one of a plurality of differing boom connectors thereto.