The present invention relates to a coating method to be used in a fluid and an apparatus for laying a coating in a fluid, this apparatus comprising a shield which is open on the side or sides adapted to be fitted against the surface of an object, whereby a space substantially isolated from the environment is created inside the shield when the shield is fitted against the surface of the object; and means for feeding gas into the shield.

The invention particularly relates to underwater concrete coating. In this connection, 'coating' refers to all those measures by which a new material is applied to the surface of a certain repair or building object, which means that it is not necessarily a question of a surface layer intended as a permanent outer structural layer but that it is possible, case by case, to produce many successive structural layers of different materials onto the object.

A method is previously known for performing underwater concrete coating. In said known method the coating is commenced by building a mould around the object to be repaired. After this, the repair material, concrete for example, is run through hoses into the mould, in which situation the mould will prevent the concrete from being washed away from the object to be repaired during hardening. The greatest drawback with this known method is that the mould is difficult to construct. Constructing and mounting the mould is extremely slow and expensive because said measures have to be mainly performed under the water surface, which greatly impedes the process. Another drawback with this known method is that despite the mould, some of the

repair material will be washed away during hardening, especially with those objects that are exposed to the flow of water.

It is the object of the present invention to remove the above-mentioned problems and to provide a method by which the coating to be carried out under the water surface (or some corresponding substance) can be performed considerably more easily and quickly than by the known methods. These objects are achieved with the method of the invention, which is characterized in that the shield is fitted against the surface of an object, the shield being open on the side or sides against the surface of the object, whereby a space substantially isolated from the environment is created inside the shield by means of the shield and the surface of the object; gas is fed to the interior of the shield in order to replace the fluid contained therein by gas, whereby the gas feed causes the fluid to be discharged from the shield, and the coating is sprayed onto the object through a spray nozzle located inside the shield while continuing feeding gas into the shield by mixing gas with the sprayed coating.

The invention further relates to an apparatus by which the method of the invention can be used. The apparatus of the invention is characterized in that the apparatus comprises a spray nozzle for spraying the coating onto the object covered by the shield, whereby the shield comprises a common inlet for gas and coating, that is to say the spray nozzle. The space essentially isolated from the environment created inside the shield refers to a situation where the shield and the surface of the object isolate the space inside the shield well enough for the fluid to be removed from this space by feeding gas into the shield. Thus it is possible for the shield to have

small holes if necessary in order to enable the discharge of the fluid and any extra gas, and it is not necessary for the contact area of the shield and the object to be absolutely liquid proof. Experimental checks have shown that there can be a gap of at least 15 mm in width at said contact area without this having a considerable effect on the spray concreting performed by the apparatus.

The invention is based on the idea that underwater coating will become considerably easier and quicker compared to prior art methods now that coating is performed by creating a gas space (advantageously an airspace) at the object, after which it is possible to spray the coating onto the object, in which case it is not necessary to build a separate mould around the object. Since the coating material is taken onto the object by spraying, the coating material will pack considerably more tightly onto the object compared to known solutions, which involve running the coating material into a mould. Due to tighter packing, the coating material will stay well in place on the object and will not wash away during hardening. The most remarkable advantage of the method and apparatus of the invention is thus that coating can be performed considerably more quickly and simply than by the known methods. Since the gas is sprayed into the shield through the same inlet as the coating, it is possible to use the kinetic energy of the gas for spraying the coating. Using one inlet also enables using spraying equipment known as such for feeding the coating into the shield.

In a preferred embodiment of the apparatus of the invention, the spray nozzle is journalled to turn in relation to the shield. Thus it is possible to use a shield which covers a considerably larger area of the

object than what can be coated by a spray nozzle at a time because it is thus possible to direct the spray nozzle by turning it towards the different parts of the surface of the object covered by the shield. In another preferred embodiment of the apparatus of the invention, the shield is at least partly made of a transparent material, which allows the diver operating the apparatus to follow the coating process through plastic inspection doors for instance. In a third preferred embodiment of the apparatus of the invention, special sealing equipment has been fitted on the edges of the shield in order to provide better tightness between the edges of the shield and the surface of the object. In a fourth preferred embodiment of the apparatus of the invention, the apparatus comprises special recoil removing means by which the shield is pressed towards the surface of the object. This facilitates holding the apparatus in place during coating.

The preferred embodiments of the method and apparatus of the invention are disclosed in the appended dependent claims 2 - 3 and 5 - 8. In the following the invention will be described in greater detail by means of a few preferred embodiments of. the invention with reference to the accompanying drawings, in which

Figure 1 shows a preferred embodiment of the apparatus of the invention,

Figure 2 shows another preferred embodiment of the apparatus of the invention, and

Figure 3 shows a third preferred embodiment of the apparatus of the invention.

Figure 1 shows a preferred embodiment of the apparatus of the invention while being fitted against an object 2 under the water surface. A side view of the

apparatus in Figure 1 shows a shield 1 in the shape of a truncated cone made of steel plates. The shield 1 is presented as cross-cut in Figure 1. The diameter of the open side of the shield (the side fitted against the object 2) is about 35 cm. A slit is formed on the edges 3 of the shield 1 touching the object, and a hose-like rubber packing 4 is fitted in said slit. An air hose 5 is connected to the rubber packing, which allows the diver operating the apparatus to fill the hose-like packing 4 with air after the shield 1 is fitted in order to provide better tightness between the shield 1 and the object 2. Due to air filling, the rubber packing fills up to follow the roughnesses on the surface of the object. Experimental checks have, however, shown that it is not necessary for the gap between the edges 3 and the surface of the object 2 to be absolutely liquid proof but that said gap can be even 15 mm in width in places without the quality of the spray concreting performed by the apparatus suffering from this. A through hole 7 is made in the truncated cone shaped shield 1 in order to fit a spray nozzle 8 in the shield. To the spray nozzle 8 is connected a connecting pipe 9 through which air and/or concrete is conveyed to the spray nozzle. The connecting pipe 9 comprises a check valve 10 to cut off the feed of air and/or concrete. A suitable brand of concrete to be used would be some type of concrete insoluble in water, a brand of concrete available at Porvoon Vesirakennus Oy (Vanha Porvoontie 231 E, 01380 Vantaa, Finland), for instance. Transparent plastic windows 11 have been fitted in the upper and lower parts of the shield 1 through which the diver can follow the coating process. In order to keep the shield 1 pressed against the surface of the object 2 during coating, the apparatus shown in Figure 1 comprises recoil removing means 12. Said means

comprises a pump the suction face of which is on the side of the shield, that is, on the right in Figure 1, and the outlet side of which is away from the shield, that is, on the left in Figure 1. The arrow drawn in the recoil removing means 12 indicates the pumping direction thereof. The recoil removing means 12 thus produces a faint flow in the water surrounding the apparatus while pressing the shield tighter against the surface of the object 2. The recoil removing means is not necessary in situations where the amount of concrete sprayed by the apparatus is about 10 - 20 m ³ /h because in this case the diver is able to hold the apparatus in place manually during spraying.

In using the apparatus shown in Figure 1 for coating the object 2, the order of steps is as follows: the shield 1 is fitted against the surface 2, the packing 4 is filled with air, the recoil removing means 12 is started (not always necessary), - air is blown through the nozzle 8 at a pressure of about 6 - 10 bars (depending on the depth), whereby the water in the shield 1 (and any excess air) is discharged through the edges of the shield 3 and the surface 2, concrete and air are sprayed through the nozzle 8 onto the surface of the object 2, in which case the amount of concrete to be sprayed is for instance about 10 - 20 m ³ /h and the amount of air 8 - 10 m ³ /min, the sprayed concrete packing against the surface 2 while the air is discharged through the gap between the surface 2 and the edges 3, when the area of the surface 2 covered by the shield 1 has been coated, the spraying of concrete and air is finished, after which the shield 1 is transferred to another place and the steps described above are repeated.

It is also possible to use a shield which covers a considerably larger area than what can be coated by the spray nozzle 8 at one time. In this case, the spray nozzle 8 is preferably journalled at the inlet 7 to turn in relation to the shield so that the position of the spray nozzle can be altered during spraying by moving the pipe 9. The spray nozzle 8 can also preferably be movable in relation to the shield 1, in which case it can be moved for instance vertically and horizontally in relation to the shield.

In order to hold the shield in place with less

, effort, it can be provided with a special depth adjuster, in which case said depth adjuster will keep the shield in the required depth during spraying, thus facilitating the work of the diver (or the diver robot). The depth adjuster (not shown in the figures) can consist for instance of a tank filled with compressed air mounted on the upper part of the shield and/or weights mounted on the lower part of the shield, in which case adding weights and/or altering the amount of air in the tank will affect the floatability of the coating apparatus.

Figure 2 shows another preferred embodiment of the apparatus of the invention. Figure 2 shows a shield 13 seen from above and a cylindrical pile 14, which in the case shown in the figure is being coated by the concrete fed through the pipe 9. It is apparent from Figure 2 that the edge shapes of the side of the shield 13 fitted against the pile 14 differ from those of the shield shown in Figure 1 so that the shield 13 would better follow the surface of the pile 14 to be coated. The edges of the open side of the shield 13 are thus curved. Accordingly, it is necessary to choose the edge shape of the open side of the shield primarily on the basis of the shape of the object surface to be coated

so as to achieve the best possible result. For instance, in order to coat the corner of an angular pile, that is, a pile of a square cross section, it is necessary to choose a shield the edges of the open side of which are shaped to correspond to the shape of the angle to be coated.

In accordance with the invention, it is also possible to use a shield made of an elastic material, such as rubber, in which case said shield will adjust itself to most different shapes of the object surface due to the elasticity thereof.

Figure 3 shows a third preferred embodiment of the apparatus of the invention. The embodiment shown in Figure 3 is nearly identical to the one shown in Figure 1, but in the case shown in Figure 3, a hole 15 is shaped in the lower part of the shield so as to facilitate the discharge of excess coating material. In addition, the lower part of the shield is shaped so as to slant towards the hole 15. Thus it is possible for any excess coating material that will not adhere to the object 2 but will accumulate in the bottom of the shield 1 to be discharged from the shield. The discharge is assisted by the gas fed into the shield. If necessary, it is possible to provide the hole 15 with a back pressure valve (a flap for instance), in which case the liquid surrounding the shield will not flow into the shield through the hole 15.

It will be apparent that the method and apparatus of the invention have been illustrated above only by way of example with reference to concrete coating, and are not to be so restricted. Thus it is possible for said liquid to be instead of water quite as well some other liquid stored in a tank for instance, in which case by the method of the invention it is possible to coat the inside of the tank without it being

necessary to empty the tank. It is naturally possible to use some other gas than the air mentioned by way of example above. It is also not necessary to use concrete as coating material but it can quite as well be for instance paint or some other coating suitable to be laid by spraying that dissolves poorly or not at all in the liquid surrounding it. The preferred embodiments of the method and apparatus of the invention can thus vary within the scope of the appended claims.