Patent Description:
According to another aspect, the invention also relates to a method for using said cutter head according to claim <NUM>.

It is commonly known in the art to use cutter heads for dredging purposes. The cutter head is used solely for cutting the water bottom. A separate pump, or a plurality thereof, is provided for pumping away the mixture of solid material and water. <CIT> and <CIT> both relate to such cutter head arrangements.

Such known set up has a disadvantage in that the suction action is insufficient if the pump is positioned away too far from the cutter head. Positioning the pump close to the cutter head is no option, since the pump preferably is positioned above water level.

Tendency of most manufacturers is to apply stronger pumps which increases costs.

An alternative embodiment is described in Dutch patent application <CIT> relating to a cutter head with blades that are shaped such that a pumping action is provided upon rotation of the blades. This pumping action adds to the suction force of the pump allowing one to remove substantially all solid material that has been cut loose by the cutter head. The regular pump, that is commonly placed above water level, may be embodied smaller than pumps in common arrangements, like <CIT>.

The invention aims at providing an improved cutter head of the kind mentioned in the preamble.

The invention further aims at providing a cutter head that provides a still stronger pumping action by the cutter head itself.

So as to obtain at least one of the above mentioned aims, the invention provides a cutter head comprising the features of claim <NUM>. This cutter head has the advantage that a very high pumping action is obtained. As a consequence, a pump for transporting the mixture of solid material and water may have a smaller capacity than is required with known cutter heads or may be omitted completely. The pumping action is even higher than the pumping action obtained according to <CIT>, leading to less solid material lost when using the cutter head. A more efficient action is therefore obtained.

It has shown that the cutter head according to the present invention is able to remove all solid material that has been cut loose by the cutter head. Hence, no material is lost.

The invention therefore relates to a cutter head for removing a mixture comprising water and solid materials from a water bottom, said cutter head being rotatable around a rotation axis, said cutter head comprising blades helically placed around the rotation axis with a leading edge at a position directed away from said rotation axis, for collecting and transporting said mixture, characterized in that the blades extend from a central axis positioned near the rotation axis towards the leading edge for providing a substantially continuous transport route towards a tube connected to said cutter head, such that said mixture is transported between a first side of a first blade part and an opposite side of an adjacent second blade part towards the tube connected to said cutter head. An advantageous effect of the cutter head according to the present invention is obtained by the fact that the blade extends from the leading edge to a position at the rotation axis, leaving no free space between two successive passes of the blade parts. As a result, material is locked up in a transport route defined by two facing surfaces of blade parts.

The cutter head according to the invention preferably comprises cutting means, wherein the leading edge of the blade is provided with said cutting means.

So as to obtain a maximum pumping action by said blade, it is preferred that the leading edge of the blade is directed substantially into a rotation direction of the cutter head. Since the blade extends towards the rotation axis, any mixture can only leave the cutter head through the transport route defined by the blade towards the tube, yielding a pressure inside said tube and as a consequence a positive head to the pumping action.

A smooth operation yielding both a high pumping capacity and an optimum cutting action is obtained when the leading edge of said blade substantially fits a rounded cone. The cutting means then have a good grip on the water bottom to be dredged.

It is especially preferred that the rotating blades provide a guiding surface between the leading edge and the central axis and directed towards a position between said leading edge and said central axis, since that yields an instant pumping action to material cut away from a water bottom, wherein in addition material that is cut subsequently helps in transporting said material through the transport route defined by the blade towards the tube.

So as to obtain a stronger pumping action and an increased cutting speed, it is preferred that the cutter head according to the invention comprises blades in a double pitch, a triple pitch or a quadruple pitch.

In a cutter head with multiple blades, it is preferred that all blades are shaped substantially identically, such that upon rotation of the cutter head said mixture is transported between a first side of a first blade and an opposite side of an adjacent second blade towards the tube connected to said cutter head.

An embodiment wherein said cutter head and said tube are coupled and mutually rotatably driven is preferred, since this allows to drive the tube, for example by a coaxial motor, simultaneously driving the cutter head.

It therefore is further preferred that the tube is driven by means of a motor, preferably a coaxial motor, positioned at an outside of the tube.

In the cutter head according to the invention, said tube comprises a transport screw with at least one blade, the at least one blade being an extension of the at least one blade of the cutter head. Since the rotating blades are positioned partly inside the tube, the mixture of water and solid material is more effectively guided into the tube at a higher velocity so that the solid materials do not fall back towards the cutter head. Clogging is thus effectively prevented.

According to a further aspect, the invention relates to a method of dredging a water bottom by using a cutter head according to the present invention, said method comprising the steps of positioning said cutter head on said water bottom, and rotatably driving said cutter head so as to cut the water bottom and pumping an obtained mixture of solids and water through said tube by means of a pumping force induced by the blades of the cutter head. The effects and advantages that are obtained with a cutter head as mentioned above can be obtained with this method.

Preferably, the tube and the cutter head are driven simultaneously which can be easily obtained when the tube and the cutter head are mutually connected.

Hereafter, the invention will be further described by means of a drawing. The drawing shows in:.

The same and similar parts and features of the cutter head according to the present invention have been denoted by the same reference numerals in the figures. However, for ease of understanding the figures, not all parts that are required for a practical embodiment have been shown.

<FIG> shows a partially sectional perspective view of a cutter head <NUM> for dredging purposes and the like in a water bottom. The cutter head <NUM> comprises blades <NUM>, <NUM>, <NUM>, <NUM> to which cutting means <NUM> are provided for cutting the water bottom. In the embodiment shown in the figures, the cutter head comprises four blades <NUM>, <NUM>, <NUM>, <NUM> that are evenly distributed over the circumference of the cutter head. The blades are spirally wound around a rotation axis <NUM> (identified in <FIG>) of the cutter head, which thus is the central axis <NUM> of the cutter head <NUM>.

During use, the cutter head <NUM> is rotated along rotation axis <NUM> so as to consecutively cut the water bottom by means of said cutting means <NUM>. Generally, cutter heads <NUM> as shown in the figure are used in dredging for removing sand, rocks and the like from a water bottom. Therefore, a mixture of solid materials and water is obtained, that must be removed from said water bottom.

The blades <NUM>, <NUM>, <NUM>, <NUM> in the cutter head <NUM> according to the present invention are embodied somewhat helicoid. A plurality of blades <NUM>, <NUM>, <NUM>, <NUM> is provided, positioned symmetrically around a rotation axis <NUM>, extending from the rotation axis towards a leading edge <NUM>. Each blade covers a circle if viewed from a position on its rotation axis <NUM>, as schematically shown in the figures. Preferably, each blade <NUM> is embodied with a rake and skew (also mentioned slope and incline). As a consequence, the blades <NUM> are mutually coupled at the rotation axis <NUM>.

Each blade <NUM>, <NUM>, <NUM>, <NUM> provides a pumping action upon rotation of the cutter head <NUM>, said pumping action being dependent on the rate of rake and skew, the diameter of the blades <NUM>, <NUM>, <NUM>, <NUM> and the rotational velocity of the cutter head <NUM>.

The cutter head <NUM> is coupled to a tube <NUM>, for example through a rim <NUM>, but it may be manufactured as a single body as well. A rotation axis of said tube <NUM> is aligned with the rotation axis <NUM> of said blades <NUM>, <NUM>, <NUM>, <NUM>.

Due to the shape of the blades <NUM>, <NUM>, <NUM>, <NUM>, a pumping action is obtained upon rotation of the blades <NUM>, <NUM>, <NUM>, <NUM>. A leading edge <NUM> is directed into the rotational direction of the cutter head <NUM>. The blade <NUM> may bend progressively from the leading edge <NUM> towards the tube <NUM>, but a uniform bending is possible as well. The pumping action induced by the blades <NUM>, <NUM>, <NUM>, <NUM> on the mixture of water and solids is dependent on such shape of the blades. Furthermore, due to the shape of the blades, mixture of water and solid materials is directed towards the inside of the cutter head <NUM> and therefore directly towards the tube <NUM>, such that all mixture will be transported efficiently. The pumping head provided by the shape of the blades <NUM>, <NUM>, <NUM>, <NUM> of the cutter head <NUM> work together with the propelling action of the said blades <NUM> yielding a very efficient pumping effect. The pumping head provided by the cutter head of the present invention is significantly larger than the head obtained with any of the known cutter heads. This relieves the regular pump or may even allow shutting off the regular pump. A huge advantage is the cost reduction for pumping gear.

As shown in <FIG>, the cutting means <NUM> are provided on the leading edge <NUM> of each blade <NUM>, <NUM>, <NUM>, <NUM>.

As mentioned above, <FIG> shows a partly sectional side view of the cutter head <NUM>. The rake and skew of each blade <NUM> are clearly visible in <FIG> and also in <FIG>.

The partially sectional side view of <FIG> clearly shows that the blades <NUM> are mutually connected at first position <NUM>. A connecting member <NUM> is provided to which all blades <NUM> are connected at their respective top part. As a matter of fact, the blades <NUM>, <NUM>, <NUM>, <NUM> may be manufactured as a unitary body, as a result of which said connecting member <NUM> can be omitted.

<FIG> clearly shows that the blades <NUM>, <NUM>, <NUM>, <NUM> extend to a position beyond the cutter head <NUM> inside the tube <NUM>. More in particular, the tube <NUM> is provided at its inside with a continuation <NUM> of the blades <NUM>, <NUM>, <NUM>, <NUM>. As a consequence, the mixture of water and solid material is effectively guided into the tube <NUM> where clogging or blockage, due to solid material falling back towards the cutter head <NUM>, is effectively prevented. It is not necessary that part <NUM> also provides a pumping action. It may be sufficient for part <NUM> to guide said mixture through the tube <NUM>, although some additional pumping action provided by part <NUM> may help to more effectively transport said dredged mixture.

Claim 1:
A cutter head (<NUM>) with a tube (<NUM>) for removing a mixture comprising water and solid materials from a water bottom, said cutter head being rotatable around a rotation axis (<NUM>), said cutter head comprising blades (<NUM>, <NUM>, <NUM>, <NUM>) helically placed around the rotation axis with a leading edge (<NUM>) at a position directed away from said rotation axis, for collecting and transporting said mixture,
wherein
the blades extend from a central axis positioned near the rotation axis towards the leading edge for providing a substantially continuous transport route towards a tube connected to said cutter head, such that said mixture is transported between a first side of a first blade part and an opposite side of an adjacent second blade part towards the tube connected to said cutter head,
characterized in that said tube (<NUM>) comprises a transport screw (<NUM>) with at least one blade, the at least one blade being an extension of the at least one blade of the cutter head.