BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to underwater hull cleaning of floating vessels, and more particularly to a rotary brush for removing barnacles and other fouling from the hull of a ship.
2. Review of the Problems and the Prior Art
The fouling of hull surfaces is a major concern to ship owners. For example, it is well known in the shipping industry that the speed of a vessel can be increased by removing the fouling from its hull. If a ship is prepared to embark on a relatively lengthy journey, a heavily fouled hull can increase its fuel consumption and transit time, thus resulting in a substantial loss of income to the shipowner.
If the hull is fouled with algae or grass for example, it can be cleaned relatively easily with a variety of presently available equipment. Barnacles, however, are a particular nuisance to ship owners because they are difficult to remove without damaging the hull paint. At the present time, hull cleaning may be done by rotary disc brushes with bristles made of nylon or wire. If the hull is moderately fouled, as with algae or grass, it can easily be cleaned with a nylon brush. But, a nylon brush alone cannot remove barnacles. Moreover, a wire brush is capable of removing barnacles, but not without damaging the paint coating on the hull, which paint coating is provided to prevent corrosion and fouling, and is effective as a corrosion preventive only so long as it is intact. Underwater vacuum cleaners may be used to remove grass and algae from the bottoms of small pleasure craft, but this equipment is likewise incapable of effectively removing barnacles. Rotary brushes having wire bristles interspersed among slightly longer nylon bristles have been used to remove barnacles, but, as the nylon bristles wear out, the wire bristles eventually come into contact with the hull paint and remove such paint as well as hull fouling growths.
Large commercial vessels are drydocked at regular time intervals for routine hull maintenance. A hull fouled with barnacles is usually cleaned by rotary wire brushes or wire scrapers which remove the hull paint; this removal of paint is not objectionable because repainting the hull normally is included in the hull maintenance operation. The point is that hull fouling often necessitates drydocking at intervals more frequent than would otherwise be necessary. Consequently, commercial ship operators often apply antifouling paints to the hulls of their vessels in an effort to extend the period between drydockings for the purpose of hull cleaning. These paints contain toxic substances which prevent the growth of plant and animal life. The more effective antifouling paints, particularly the copper base and vinyl or epoxy types, are extremely costly, however. Inexpensive grades of antifouling paint are available, but they become relatively ineffective after a few months at sea. Where expensive antifouling coatings are used on the vessel, existing while-afloat hull-cleaning procedures and devices cannot be used to advantage to remove barnacles, because such procedures and devices also remove the hull coating. Therefore, because drydocking a vessel is costly (both per se and in terms of lost vessel operating time) and because existing barnacle removing devices also damage or remove hull paints or coatings, a need exists for a device which can be used effectively, while the vessel is afloat, to remove barnacles and other fouling growths without harm to underlying hull coatings.
SUMMARY OF THE INVENTION
This invention provides a brush which is capable of removing barnacles from the hull of a ship without damaging an underlying paint coating. The brush can be easily stored aboard ship and requires a relatively small capital investment. The invention is adaptable for cleaning all types of vessels, regardless of their service requirements, but it is particularly useful for cleaning drilling vessels because they generally experience acute hull fouling problems. Drilling vessels tend to remain in one area of operation for extended periods of time before relocating. Since the accumulation of plant and animal life on hull surfaces depends upon the relative inactivity of the vessel (most fouling growths appear on a ship hull while the ship is inactive in port), drilling vessels are usually heavily fouled by the time they are ready to proceed to a new area of operation. The use of this invention allows the vessel to be cleaned while it is afloat and before it proceeds to its next location. As a result, no damage is done to the hull surface, transit time between jobs is minimized, fuel economy is maximized, and the necessity of drydocking the vessel to remove fouling growths is avoided.
Briefly, the brush contemplated by this invention has a base with an obverse surface and a plurality of bristles extending away from the base obverse surface to free ends spaced from the obverse surface. At least one metal element having a substantially straight working edge is secured to the base by mounting means positioning the working edge a selected distance toward the base obverse surface from the free ends of the bristles and substantially parallel to the obverse surface.
The preferred form of the invention includes means for rotating the base about an axis substantially normal to the obverse surface. Preferably, the metal element mounting means includes a resilient element disposed between the metal element and the base. The mounting means is also preferably adjustable to vary the distance from the base obverse surface to the working edge of the metal element.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features of this invention are more fully set forth in the following detailed description of certain presently preferred embodiments of the invention, which description is presented with reference to the accompanying drawings, wherein:
FIG. 1 is a perspective view showing the hull-cleaning brush of this invention and drive unit therefor;
FIG. 2 is a perspective view showing the hull-cleaning brush;
FIG. 3 is a fragmentary elevation view of one embodiment of the brush;
FIG. 4 is an enlarged fragmentary cross-sectional elevation view of the structure shown in FIG. 3;
FIG. 5 is an enlarged fragmentary elevation view of an alternative embodiment of the brush;
FIG. 6 is a perspective view showing a further alternative embodiment of the brush; and
FIG. 7 is a fragmentary elevation view of the structure shown in FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a rotary hull-cleaning brush 10 according to this invention comprises tufts of flexible bristles 12 projecting outwardly from a obverse surface 11 of a disc-shaped baseplate 14. The bristles preferably consist of nylon or some other nonmetallic filament material, but metal bristles may be used if desired; the degree of bristle stiffness may be adjusted depending upon many factors, including the nature of the materials to be removed from a particular ship hull. Preferably, the baseplate is constructed of marine grade plywood which has the desirable attributes of strength, buoyancy, and low cost; however, any structural material having these characteristics may be used, such as plastic, for example. A plurality of spaced-apart resiliently mounted metal elements or impacting blades 16 are secured to obverse surface 11 of baseplate 14 adjacent to its outer periphery. In one embodiment of the invention shown in FIGS. 3 and 4, the impacting blades 16 are defined by suitable lengths of heavy-duty angle iron segments defining a series of upper working edges 18 disposed outwardly from obverse surface 11 of the baseplate 14 a selected distance inwardly of the unsupported ends of the bristles toward the obverse surface of the baseplate. The blade working edges 18 are rounded to avoid unnecessary gouging of the paint on a ship hull in the event a blade happens to strike the hull surface during cleaning operations.
An elongated, transversely circular shaft 20 projects outwardly from the lower (i.e., reverse) surface 21 of baseplate 14 along a line normal to base obverse surface 11. In use of the brush, shaft 20 is coupled to the output shaft of a pneumatic motor (not shown) for rotating the brush during hull-cleaning operations. A buoyant casing 22 encloses the motor and any gearbox assembly associated with the motor. Casing 22 has sufficient positive buoyancy to render the entire combination of the brush, the motor and the casing substantially neutrally buoyant and readily manipulated by a diver operator. The casing is preferably hemispherical in shape to bring the center of buoyancy of the entire brush combination close to its center of gravity, thereby increasing the ease with which the brush is handled under water. The hemispherical shape of the casing also eliminates any corners which might otherwise be exposed to damage. A pair of elongated handles 24 and 25 project laterally outward from the casing to provide means for manually applying the brush to the hull surface. Handle 24 additionally provides a connection 26 for cooperation with the end of a compressed air supply base 27 via which compressed air is supplied from a compressor (not shown) to the motor for operating the motor. Exhaust air from the motor is led away from the motor by a second hose 28 connected to handle 24 adjacent to the motor casing; alternatively, exhaust motor air may be vented from the motor through the casing, but this arrangement is not preferred since direct venting of exhaust motor air through the casing reduces visibility of the work area for the diver operator. The speed of the air motor is adjusted by a pneumatic pressure regulating device operated by a hand lever 30 mounted on a handle 24.
In the embodiment of the invention shown in FIGS. 3 and 4, each impacting blade 16 is supported on obverse surface 11 of baseplate 14 by mounting means in the form of a wedge-shaped rubber mounting block 34 and a plurality of flat removable shims 36. A bolt 38 extends downward through the lateral base of the impacting blades, the rubber block, the shims, and the baseplate where it cooperates with a nut 40 to secure the blade to the base plate. The nut is set in a recess 42 in the lower surface of the baseplate.
The working edges 18 of the impacting blades 16 are spaced about 1/8 inch to 3/16 inch inwardly toward obverse surface 11 of baseplate 14 from the tops of bristles 12. It is desirable to maintain this spacing during cleaning operations so that the bristles continuously contact the hull surface and serve to space the blades slightly from the hull. Thus, when the rotary brush of this invention is applied in use to a hull surface fouled by barnacles and the like, the impact force of the blades shears off the barnacles at their base approximately 1 /16 inch outboard of the hull surface. As a result, a 1/16 inch thick "dime" is left on the hull surface and the hull paint is not damaged. If the barnacle is removed intact from the hull, the paint also will be removed. Shims 36 are removable as desired to maintain proper spacing between the blades and the bristle ends as the bristles wear during continued use of the brush. The shims preferably are constructed of stainless steel in order to prevent rusting.
When the brush is rotated during cleaning operations, it rotates in a counterclockwise direction as illustrated by the arrow at the top of FIG. 3. Preferably, the rubber mounting blocks 34 are disposed on base 14 so that their upper surfaces, with which the blade bases are engaged, slant away from the direction of brush rotation. The mounting blocks permit the blades to deflect angularly inward toward the baseplate and away from the direction of brush rotation in the event the blades strike a stationary object on the hull surface, such as a rivet head for example. Each bolt 38 is disposed within a cylindrical metallic sleeve 44 which extends substantially concentric to the bolt shank through the blade base, the rubber block, and the shims to base 14. The space between each sleeve 44 and bolt 38 is filled with the rubber to allow the bolt to deflect laterally of its length, thereby reducing fatigue failure of the bolts during use of the brush.
FIG. 5 shows an alternative arrangement for resiliently mounting the impacting blades to the brush base. In this embodiment of the invention an impacting blade 46 is comprised of an angle iron segment 48 having an elongated arcuately curved base flange 50. Flange 50 is curved concave away from baseplate 14. The blade is spaced from the baseplate by a plurality of removable shims 36. A bolt 52 extends downward through flange 50, the shim stack, and baseplate 14 into a recess 54 in the reverse side of the baseplate where it cooperates with a washer 56 and a nut 58 to secure the blade to the base. A coil spring 60 is disposed between the baseplate and the washer about the bolt shank. During use of the brush shown in FIG. 5, if the blade working edge 18 strikes a stationary object, the blade base flange rocks along the adjacent shim against the tension provided by spring 60. The shock mounting of the blade thus prolongs the useful life of the blades and reduces the vibration produced by the brush.
FIGS. 6 and 7 show another embodiment of the invention wherein an impacting blade 62 comprises a segment of heavy-duty steel plate defining an upper working edge 64 rounded at one end to avoid gouging the hull paint during use; the rounded end of the blade preferably is located toward the circumference of baseplate 14 when connected to the baseplate. A pair of elongated steel mounting plates 66, each having a threaded central bore 68, are integral with each of the opposite ends of the blade remote from working edge 64. Each mounting plate 66 extends laterally of the generally planar blade. The bottoms of the impacting blade and the mounting plates define a flat base surface 70, with the blade being disposed so that it slants upwardly with respect to base surface 70. Each mounting plate defines an arcuately curved upper surface 72 curved convex away from base surface 70. The blade and mounting plate combination is bonded to a rectangular rubber mounting block 74 by vulcanizing the lower portion of the impacting blade and substantially the entire portion of each mounting plate into the top of mounting block 74. The exposed portion of the impacting blade slants away from the direction of rotation of base 14 in use of the device, upwardly relative to the upper surface of the mounting block, and the arcuate upper surfaces 72 of the mounting plates extend slightly above the upper surface of mounting block 74 as shown in FIG. 7. Impacting blade 62 and rubber mounting block 74 are supported on obverse surface 11 of baseplate 14 by a plurality of removable shims 76. The blade is secured to the baseplate by a pair of mounting bolts 78 each extending through a respective bore 68 in mounting plates 66 and through cooperating holes in mounting block 74, shims 76, and baseplate 14 to the reverse side of the baseplate where it cooperates with a washer 80 and a nut 82. The head portion of each bolt 78 has an arcuately curved lower bearing surface 84 curved concave away from the cooperating curved upper surface 72 of mounting plate 66.
During use of the brush having the blade arrangement shown in FIGS. 6 and 7, if the blade working edge 64 strikes a stationary object the blade deflects relative to mounting block 74 inward toward the baseplate 14 away from the direction of brush rotation indicated by the arrow in FIG. 7. During inward deflection of the blade, the curved bearing surfaces 84 of each bolt 78 are free to rock along the adjacent curved upper surface 72 of its respective mounting plate 66, thereby reducing fatigue failure of the bolts during use of the brush. The configuration of mounting plates 66 provides means for securely bonding the blade to the block so that the possibility of blade separation therefrom is substantially reduced. Although impacting blade 62 could be disposed in a position normal to baseplate 14 without departing from the scope of this invention, a slanted position relative thereto is preferred because it reduces the amount of inward deflection when the blade strikes a stationary object, thereby exerting less load on the blade and its mounting bolts and reducing the magnitude of vibration transmitted to the operator of the brush.
In view of the foregoing description, it is apparent that this invention provides an improved brush for use in efficiently and effectively cleaning the submerged surfaces of ship hulls and the like fouled by marine plant and animal growth. The bristles of the improved brush function to remove plant and most animal growths, and the impacting blades function to remove barnacles and the like in a manner which is both effective in terms of hull smoothness and conserving of the integrity of the paint coat of the hull. Also, the resilient mounting of the impacting blades to the brush base minimizes the extent to which the impacting blades may scratch and remove hull paint; such mounting also reduces shocks and vibrations transmitted to the person operating the brush. The brush is particularly useful in that it may be used by a diver to clean a ship hull while the ship is tied up at a dock working cargo. Thus, it is no longer necessary to drydock the vessel and thereby move the vessel from useful service, for the purposes of effectively cleaning the vessel of marine growths which produce economic loss to the vessel operators. Also, since the brush is constructed to preserve to the greatest extent possible the hull paint coating, the vessel need be drydocked for repainting at less frequent intervals.
The invention has been described above with reference to certain specific structural arrangements which, while constituting the presently preferred embodiments of the invention, are not the only embodiments in which the invention may be manifested. Other structural arrangements effectively equivalent to the arrangements described above will be apparent to workers in the relevant art and technology. Accordingly, the foregoing description alone should not be interpreted as defining the precise limits of the invention.