The invention relates to a cutter head according to the preamble of Claim 1. Such a device is known for in ^¬ stance from EP 1978160. In the known device, the cutters are next to each other and the cutters do not make the un ^¬ derwater objects sufficiently small so that the pump can suck them up.

In order to prevent this drawback, the cutter head is in accordance with Claim 1. By using two counter rotating cutters with rings with cutter teeth that intersect, the cutters reduce the underwater objects that extend above the soil to small parts that can be sucked up in the suction mouth .

In accordance with an exemplary embodiment, the cutter head is in accordance with Claim 2. In this way, the cutter teeth transport the loosened material of the underwater ob ^¬ jects directly to the suction mouth so that the cutter acts is effective in removing the underwater objects.

In accordance with an exemplary embodiment, the cutter head is in accordance with Claim 3. As a result, the side- walls support the cutters and guide the material loosened by the cutters directly into the suction mouth.

In accordance with an exemplary embodiment, the cutter head is in accordance with Claim 4. As a result, remains of an obstacle adhering to the cutter teeth are scraped off the cutter teeth by the comb and sucked into the suction mouth .

In accordance with an exemplary embodiment, the cutter head is in accordance with Claim 5. As a result, the mix- ture of loosened material and water is mainly sucked in be ^¬ tween the two cutters and the loosened material is en ^¬ trained more efficiently. In accordance with an exemplary embodiment, the cutter head is in accordance with Claim 6. As a result, encrusta ^¬ tion of material on the comb of the cutter teeth is pre ^¬ vented .

In accordance with an exemplary embodiment, the cutter head is in accordance with Claim 7. As a result, the cables can tilt the cutter head so that the cutters can approach the underwater obstacles under an angle so that cutter can remove these while moving in lateral direction.

The invention will be explained below with reference to an exemplary embodiment by means of a drawing, in which: Fig. 1 shows the cutter head according to the invention during use,

Fig. 2 shows a front view of the cutter head from Fig. 1, Fig. 3 shows a cross section along I I I - I I I of a cutter housing of the cutter head from Fig. 2,

Fig. 4 shows a cross section IV- IV of a cutter housing from Fig. 3, and

Fig. 5 shows a cross section V-V of a cutter housing from Figs . 2 , 3 and 4.

Fig. 1 shows obstacles 12 which stuck out from a soil 1 under water 13. In ancient cultivated areas, the soil 1 often contains ancient remains of bridges, foundations and the like. If new structures are to be erected and the water 13 has to be deepened, such obstacles 12 have to be re ^¬ moved. To this end, the cutter head 8 is suspended from ca ^¬ bles 7 by means of lifting eyes 18 and held upright by ca ^¬ ble 5 that is connected to a lifting eye 19. The lifting eye 19 is in a higher position than the lifting eye 18. The cutter head 8 is taken to the obstacles 12 under water 13. Near the obstacles 12, one or more cables 5 position the cutter head 8 at an angle, for example at an angle of 30° to the vertical. By positioning the cutter head 8 at an angle, cutters 10 operate at a working height 11 and remove the obstacles 12 during lateral displacement.

Fig. 2 shows a front view of the cutter head 8. The cutter head 8 is composed of a pump frame 4 on top of a cutter housing 9. The pump frame 4 and the cutter housing 9 are coupled to one another by means of an intermediate frame 14 and a suction line 3. In the pump frame 4, an underwater pump (not shown) is installed which pumps the mix- ture sucked in by the suction line 3 to a flexible pressure pipe 6. The underwater pump is driven in a known manner by means of an electric motor or a hydraulic motor (not shown) .

The cutter housing 9 has a sidewall 22 and a top panel 31. Between the sidewalls 22, two cutters 10 are installed which rotate in opposite directions of rotation 15 about rotation axes 35. Hydraulic motors 21 drive the cutters 10, for example up to a maximum speed of 500 revolutions per minute. Each cutter has four rings 17 that are fitted with cutter teeth 16. The two cutters 10 together form an underside of the cutter head 8 and the cutter teeth 16 loosen or cut free parts of the obstacle 12 and pull these parts in between the cutters 10 in the cutter housing 9. The distance between the rotation axes 35 is such that the tracks of the cutter teeth 16 of the two cutters 10 partly over ^¬ lap, so that the parts of the obstacle 12 which have been loosened or cut free are comminuted between the cutters 10 so that they can be discharged by means of the underwater pump via the suction line 3.

The top panel 31 comprises a flushing water connection

2. The flushing water that is introduced into the cutter housing 9 via the flushing water connection 2, is used to flush away dirt on the cutter teeth 16 and the rings 17 in the cutter housing 9. If desired, an opening located behind an inspection flap 20 is used to check if the cutter teeth 16 are sufficiently clean and any dirt or blockage can be removed via the opening. The hydraulic lines, flushing wa- ter line and the like which are required in order to be able to use the cutter head 8 have not been shown.

Figs. 3, 4 and 5 show the cutter housing 9 in various cross sections. A cutter 10 comprises a sleeve 30 with four rings 17 which are provided with cutter teeth 16 on both sides. The sleeve 30 is rotatably installed between the sidewalls 22 by means of bearings (not shown) , with a laby ^¬ rinth seal (not shown) being provided between the sidewall 22 and the sleeve 30 in order to prevent soiling of the bearings. A top panel 31 and an intermediate panel 27 con- nect the sidewalls 22 on the upper side of the cutter hous ^¬ ing 9 and form a space with a flushing water pipe 26, the flushing water pipe 26 is connected to the flushing water connection 2. A suction mouth 25 connects the suction line 3 to a space below the intermediate panel 27. The suction mouth 25 has a centreline 34 that has the same direction as the direction of movement of the cutter teeth 16 between the cutters 10 where the movement of the cutter teeth 16 overlaps .

The cutters 10 are positioned in the space below the intermediate panel 27 between the sidewalls 22. Near each cutter 10, a comb 24 is positioned between the sidewalls 22 and the comb 24 forms a gap 33 with the sleeve 30 of the cutter 10, this gap 33 forms a seal such as a labyrinth seal. The comb 24 has openings 23 through which the cutter teeth 16 and the rings 17 can rotate. A baffle plate 32, which encloses the cutter 10 and the cutter teeth 16, runs with play from the comb 24 up to a side panel 34. The combs 24 and the baffle plates 32 ensure that water that is sucked in by the suction mouth 25 is mainly sucked in from between the two sleeves 30 so that material that has been loosened by the cutter teeth 16 and that moves with the cutter teeth 16 in the direction of the suction mouth 25 is sucked in the suction mouth 25.

The comb 24 also ensures that the material adhering to the cutter teeth 16 is loosened and is sucked away in the suction mouth 25. Spray nozzles 29 are provided on the comb 24, between the openings 23. Pressure pipes 28 connect the spray nozzles 29 to the flushing water pipe 26. The water jets from the spray nozzles 29 clean the cutter teeth 16 and ensure that loosened material is sucked away by the pump via the suction mouth 25.

In the above-described exemplary embodiment, the cut- ters 10 are designed with sleeves 30 that are cylindrical. It will be clear that the cutter head 8 works in a similar way if the cutters 10 have a different shapes. The sleeve 30 of the cutter 10 may be conical instead of cylindrical which means that the cutter teeth 16 are arranged on rings