US3860987A

US3860987A - Device for applying a protective coating to an immerged surface

Info

Publication number: US3860987A
Application number: US358343A
Authority: US
Inventors: Peter Bolli; Jean-Jacques Asper
Original assignee: Battelle Memorial Institute Inc
Current assignee: Battelle Memorial Institute Inc
Priority date: 1972-05-10
Filing date: 1973-05-08
Publication date: 1975-01-21
Anticipated expiration: 1992-01-21
Also published as: IT985870B; BE799321A; GB1409837A; CH566824A5; JPS4948095A; FR2184352A5; ES414571A1; DE2323606A1; NL7306458A

Abstract

A coating applicator for the painting of underwater surfaces comprises a rotary brush whose hollow body, mounted on the shaft of a driven motor, has a chamber communicating with a source of paint under pressure. A bunch of bristles on the brush body is supplied with paint from the chamber via flexible tubes terminating just short of the bristle tips. A peripheral array of relatively hard bristles may receive another reagent, e.g., a solvent, from a separate compartment of the brush body while an inner core of harder bristles is supplied with paint.

Description

United States Patent 1191 [111 3,860,987

Bolli et a1. Jan. 21, 1975 [54] DEVICE FOR APPLYING A PROTECTIVE 2,682,067 6/1954 Coleman 15/29 COATING O AN IMMERGED SURFACE 3,084,069 4/1963 S1rnon 15/29 X 3,153,799 10/1964 W|lllams /29 [75] Inventors: Peter Bolli; Jean-Jacques Asper,

both f Geneva, Switzerland FOREIGN PATENTS OR APPLICATIONS Assigneez Banene Memorial Institute, 601,732 8/1934 Germany 15/29 l Carouge Swltzer and Primary Examiner-Edward L. Roberts 1 Flledi y 8, 1973 Attorney, Agent, or Firm1(ar1 F. Ross; Herbert 21 Appl. No.: 358,343 Dubno [57] ABSTRACT Foreign Application Priority Data A coatmg applicator for the paintlng of underwater May 10, 1972 Switzerland 7009/72 Surfaces Comprises a rotary brush whose hollow body 52 US. (:1 15/29, 15/50 R, 15/180, mounted 011F119 shaft'of a driven motor, has h m- 117/111 C, 118/200 ber commun1cating w1th a source of paint under pres- 51 1m. 01 A46b 13/04 A bunch of brlsfles on e b y 1s pp q 53 Field 01 Search 15/29, 34, R, with Paint from the chamber v19 flexlble tubes rm- 117/111 114/222 118/200 nating just short of the bristle tips. A peripheral array of relatively hard bristles may receive another reagent, lvent from a se arate com artment of the [56] References Cited e a so p p brush body wh1le an inner core of harder bristles 15 UNITED STATES PATENTS Supplied with paint.

1,479,233 1/1924 Gottlieb 15/29 0 1,796,641 3/1931 Zimmerman et a1. 15/29 6 C aims, 5 Drawmg Figures WWW ms sum 10F 2 S if r, 1; r: FIG. '2

FIG. 3

DEVICE FOR APPLYING A PROTECTIVE COATING TO AN IMMERGED SURFACE This invention relates to a device for applying a protective coating to an immerged surface.

The maintenance of the hull of ships poses problems which hitherto have only partially been solved. At present it is the practice to regularly brush the hull of ships while they stay in port to clean them of the layer of dirt which deposits thereon after they have been at sea for some months, to thereby reduce the hydrodynamic resistance of the hull. As such brushing operations have to be carried out rather frequently, the layer of paint on the ships hull is gradually destroyed and removed and the metal plates of the ship s hull are attacked by corrosion. Then the ships hull must be completely or par tially repainted.

To effect a complete careenage of the ship it is necessary to put it in a dry dock. The cost of such work and the loss of profit resulting from the ships idleness are considerable so that this operation is carried out only once every to 18 months. However, obviously such rare overhauling will affect the efficiency of a ship. In fact, a ship whose hull is not very well maintained will lose after 10 to 12 months from 6 to 8 percent of its nominal speed when drive power remains the same.

By investigations made recently in the field of marine paints some producers have developed paints which dry and harden under water. There exist at present two types of such paints, namely one having only one component containing a solvent which dissolves in water, and one having a plurality of synthetic-resin-based components which harden by reaction. This is, for example, the case with the paint Uwatex (registered trademark) which hardens by chemical reaction and not by evaporation of a solvent.

However, satisfactory means for application of such paints to immerged surfaces have not yet been found. Three types of difficulties have been encountered in the paint applicators known for such purposes, namely the transportation of the paint to the immerged surface to be painted, the adhesion of the paint to this immerged surface and the difficulty of obtaining a smooth aspect of the applied layer of paint.

To ensure adhesion of the paint on an immerged surface two essential conditions must be met, namely firstly the surface must be clean and not too rough and secondly the boundary layer between the liquid and the surface to be painted must be broken.

It is therefore an object of the present invention to solve the problems encountered in the application of a protective coating to an immerged surface and to overcome at least in part the aforementioned difficulties.

This is achieved according to the present invention by providing, in a device for applying a protective coating to an immerged surface, at least one rotary brush whose body has a chamber connected to a source of coating material under pressure, this chamber communicating through at least one flexible outlet tube with a set of bristles carried on the brush body. The outlet tube or tubes terminate just short of the tips of the bristles which are relatively hard in a central zone and relatively soft in a surrounding peripheral zone, the two zones being centered on the axis of rotation of the brush body whose bristle-studded lower surface is perpendicular to that axis.

These and others features of our invention will now be described by way of example and with reference to the accompanying drawing in which:

FIG. 1 is a schematic view, partly in section, of the first embodiment;

FIG. 2 is a schematic view as in FIG. 1, showing the second embodiment;

FIG. 3 is an explanatory diagram; and

FIGS. 4 and 5 are sectional views of the third embodiment, showing it in the operative and in the inoperative position, respectively.

In FIG. 1 a paint container is indicated by R and has an outlet connected by a pipe C, to a pump P communicating through a pipe C, and a passage C, with a chamber E provided in the interior of a casing B, the passage C*, extending through a lid B, of the casing B. The bottom of the casing B supports on its outside a bunch of bristles F whereas the lid B of the casing B is secured to a plate G firmly connected to the drive shaft of a drive motor M. Before reaching the chamber E the pipe C, extends through the housing and drive shaft of the motor M which is arranged coaxially to the passage C*, leading to the interior of the chamber E.

In the illustrated embodiment the motor M and the casing B are immerged in the liquid L which may be, for example, salt or fresh water. The end of the bunch of bristles F is in contact with a surface S to be painted. The container R and the pump P may be kept out of the liquid L and may preferably be mounted on a ship (not shown).

In the diagram of FIG. 3 the hardness p of the bunch of bristles F is indicated on the ordinate and the diametrical dimension D of the bunch of bristles on the abscissa. The curve 5 shows that the bristles in the zone Z, of the bunch of bristles F are harder than in the crown of bristles Z Z' surrounding the central zone 2,.

As further shown in FIG. 1, a plurality of tubular elements 2,, t t,, are arranged in the interior of the bunch of bristles F in the central zone Z and connect the chamber E with the liquid L which is in direct contact with the surface S to be painted.

The two zones of bristles forming the bunch F are designed so as to perform two complementary functions. In fact, the zone of hard bristles Z, which receives the paint is designed to penetrate the boundary layer between the water and the surface to be painted to ensure good adhesion of the paint whereas the crown of soft bristles Z Z is designed to smooth the paint.

The operation of the illustrated device is as follows:

The container R is filled with paint having one or more components, particularly designed for application under water, such as the paints mentioned above. When a paint with several components is used it is necessary to provide a dosing and mixing unit (not shown) at the outlet of each container R containing the components. Then the assembly to be immerged formed by the casing B supporting on one side the bunch of bristles P and on the other side the drive motor M, is carried to the surface to be coated to assume the position illustrated in FIG. 1. The pump P and the motor M are started simultaneously so that the paint will flow from the container R to the chamber E while the casing B is rotatively driven. As soon as the chamber E is filled with paint the pressure exerted by the pump P causes the paint to be discharged through the tubular elements 1,, t t,, which are firmly secured to the chamber E and therefore will rotate together with the bunch of bristles F. As the tubular elements terminate in the zone of the bunch F where the bristles are harder and as the bristles are rotating, the boundary layer of the water is penetrated in a circular area of the surface S which is in contact with the central zone Z, of the bunch of bristles F so that the paint leaving the tubular elements t,, t will be spread in this zone on the surface to be painted without leaving water drops enclosed between this surface and the paint, which would be prejudicial to the adhesion of the paint.

As the paint is leaving the tubular elements t,, t t the brush is moved laterally so that the bunch of bristles F is shifted while remaining in close contact with the surface S. Thereby the softer outer bristles of the peripheral crown Z Z' surrounding the zone Z, rub the layer of paint which has been spread by the harder inner bristles. By the rubbing of the softer bristles the paint is smoothed which is particularly important if the surface to be painted is the hull of a ship.

In tests which have been made with a paint having only one component we have found it possible to apply a second layer of paint half an hour after application of the first layer. Four hours after application of the second layer the paint was dry and partially hardened.

The second embodiment shown in FIG. 2 differs from the embodiment of FIG. 1 only in that it permits to add another reagent to the paint composition applied to surface S, namely a supplementary solvent or, in the case of a paint having several components, a reaction retarder designed to check the hardening of the two mixed components. This solvent or retarder is fed up to the immediate vicinity of the surface S in the peripheral zone of the bunch of bristles F,.

In this second embodiment a first container R for the paint has an outlet connected through a pipe C to the inlet of a pump P The outlet of the pump P communicates through a pipe C, and a passage C* with a chamber E, in the interior of a cylindrical casing B,, the passage C, extending through a lid B, of the casing B,. As in the first embodiment the bottom of the casing B, supports on its outside a bunch of bristles F, whereas the lid B, of the casing B, is secured to a plate G, firmly connected to the drive shaft ofa drive motor M,.

A second container R, serves to receive the solvent or reaction retarder and has an outlet connected through a pipe C to the inlet of a pump P,. The outlet of the pump P, communicates through conduits C';,, C*,, and C, with an annular chamber or compartment E provided in the casing B, around the chamber E,. As shown in FIG. 2, the pipe C* extends laterally from the drive shaft of the motor M, to the passage C which traverses the lid B', of the casing B, and opens into the annular chamber [5,.

Before reaching their respective chambers E,, E the pipes C, and C;, traverse the housing and drive shaft of the drive motor M, which is arranged coaxially to the passage C* leading to the interior of the chamber 13,.

The composition of the bunch of bristles F, is the same as that of the bunch of bristles F. The distribution diagram of the hardness p that of through the diametrical planes of the bunch of bristles along abscissa D shown in FIG. 3, thus applies also to the embodiment of FIG. 2.

In the embodiment shown in FIG. 2 two distinct groups of outlets are arranged in the interior of the bunch of bristles F,, namely tubular elements r',,

. t',, placed in the central zone of the bunch of bristles and connecting the chamber E, with the liquid L which is in direct contact with the surface S, and tubular elements r*, to t*,, placed in the peripheral portion of the bunch of bristles F, and connecting the chamber E with the liquid L in the peripheral portion of the surface S.

Thus, during operation of this embodiment of our invention the tubular elements t*, to t*,, supply a solvent whereas the paint is supplied by the tubular elements I, to r,,.

In painting an underwater surface, the applied composition on contact with the water tends to gradually stick to the outer bristles in the bunch, making them hard. It is however essential to avoid hardening of the bristles in the peripheral portion of the bunch F, to maintain the aforementioned curve of hardness e to thereby ensure a constant quality of the coating for the entire duration of paint application. It is for this reason that we supply the solvent from container R, to the peripheral region of the set of bristles F,.

When a large surface has to be coated such as the hull of a ship, a plurality of the described devices may be mounted on a common support so as to form a battery of rotary brushes.

Although the device according to the invention is particularly suitable for overhauling a ship it can obviously also be used for coating any other immerged surfaces such as the piers of bridges, gates of dams, submarine pipes and the like.

It may be desirable, both in the embodiment of FIG. 1 and in the embodiment of FIG. 2, to mount the crown of softer bristles on a support rotatable around the casing B, for example, by means of a ball bearing. In this instance the crown of softer bristles may rotate in a direction opposite to that of the casing B so as to produce a relative movement between the two zones of bristles.

In the embodiment shown in FIGS. 4 and 5, the bunch of bristles of the brush comprises a central zone of hard bristles F surrounded by a crown of softer bristles F which have free ends extending in the inoperative position beyond the free ends of the hard bristles; see FIG. 5. The greater length of the softer bristles permits them to bend until they are flush with the ends of the hard bristles F when the brush is applied to a surface S to be painted, as shown in FIG. 4. The bending of the softer bristles F helps smooth the layer of paint applied to the surface S as the boundary layer of the liquid is penetrated by the hard bristles F in the central zone of the bunch of bristles. This form of construction may obviously be applied both to the embodiment of FIG. 1 and to the embodiment of FIG. 2.

In all described embodiments the flexibility of the tubular elements 1,, t t,,, t',, t' t',, and t", 1",, serving as outlets for the coating material, is substantially the same as that of the bunch of bristles in which they are arranged so that during application of the paint they will behave substantially in the same manner as the bristles. Further, the free ends of the tubular outlet elements are somewhat withdrawn relative to the free ends of the adjacent bristles so that the bristles can slightly bend before these tubular elements contact the surface to be painted.

Although some preferred embodiments of the invention have been described herein in detail and illustrated in the accompanying drawing, it is to be understood that the invention is not limited to these precise emtively soft outer bristles on said body centered on said axis;

a source of coating composition under pressure communicating with said chamber;

at least one flexible outlet tube extending from said chamber to said set of inner bristles and terminating just short of the tips thereof; and

drive means for rotating both sets of bristles about said axis.

2. A device as defined in claim 1 wherein said body has a surface perpendicular to said axis supporting said sets of bristles, said outlet tube penetrating said surface.

3. A device as defined in claim 2 wherein said outer bristles project beyond said inner bristles.

4. A device as defined in claim 1 wherein said body is provided with a compartment separated from said chamber communicating with a supply of additional reagent, further comprising at least one other flexible tube extending from said compartment to the vicinity of the tips of said outer bristles.

5. A device as defined in claim 1 wherein the degree of flexibility of said outlet tube is substantially the same as that of said inner bristles.

6. A device as defined in claim 1 wherein said drive means comprises a motor having a shaft, said source communicating with said chamber through said shaft. l

Claims

1. A device for applying a protective coating to an underwater surface, comprising: at least one rotary brush having a body centered on an axis, said body being provided with an inner chamber; a set of relatively hard inner bristles and a set of relatively soft outer bristles on said body centered on said axis; a source of coating composition under pressure communicating with said chamber; at least one flexible outlet tube extending from said chamber to said set of inner bristles and terminating just short of the tips thereof; and drive means for rotating both sets of bristles about said axis.

6. A device as defined in claim 1 wherein said drive means comprises a motor having a shaft, said source communicating with said chamber through said shaft.