GB1578616A - Cutter for a cutter dredge - Google Patents

Description

(54) A CUTTER FOR A CUTTER DREDGE (71) I, GIJSBERTUS JAN WILLEM BOOMSTRA, of 12 Meijendelseweg, Wassenaar, Netherlands, a citizen of the Netherlands, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a cutter for a cutter dredge comprising a plurality of helically arranged cutting blades on which teeth are formed or attached to dredge very hard soil.

A known cutter of this type is formed as an open suction basket in which, between the toothed cutting blades, which are constructed as individual arms and are mounted at one end on a hub and at the opposite end on a support ring, passages to the hollow interior of the cutter are formed so that the soil which is loosened by the teeth can be passed on to the mouth of a suction tube.

The material is then passed further along the tube.

The suction basket with its open passages has the disadvantage, however, that the broken up soil is sucked up in a disorderly pattern with a large volume of water, and that the soil, once dropped back on the bottom, can hardly get in the basket through the openings between the rotary cutting blades as no intensive directional sucking action can be exerted on it. As a result, the dredged material is too sloppy with a very high water content, which is known as exhibiting a "high slop system".

The present invention overcomes the above disadvantages due to the fact that between the toothed cutting blades, helical troughs are formed, defining with the cutting blades a substantially closed peripheral surface and leading to suction orifices of a chamber formed in the rear part of the cutter to which the suction mouth of the suction tube is to be connected. Due to the troughs, a higher proportion of the cut off soil will be gathered to pass into the suction tube so that practically no slop symptom will occur.

In a preferred embodiment the chamber is defined by a portion of the rotary cutter, one or more axially disposed non-rotary screen plates laterally of the suction mouth, and a closure plate sealed to the axial plates and suction mouth perpendicular or at an angle to the cutter axis.

By the use of said chamber, the water needed for the conveyance of the soil is directionally sucked in via the troughshaped conveying channels which are filled with loosened soil so that optimum use is made of the entraining viscous action of the inflowing water, and the mixture is conducted in the direction of the suction mouth.

Besides the directional suction action, moreover, due to the rotation of the cutter in combination with the shape of the conveying channels an impelling action in the direction of the suction mouth is exerted on the material in the channels.

The provision of the above measures which lead to less slop, also offers a high degree of freedom in the shape and dimensions of the cutter and thus the possibility to deviate from the existing basket shape of cutters by, for instance, the use of a cylindrical peripheral shape of the cutter or even an anticonical shape, i.e. a taper from the rear end to the front end of the cutter.

The cylindrical as well as the tapered shape of the cutter without the new helical conveying channels would, particularly in hard soil, lead to an increase of the slop.

An axially symmetrical tapered cutter leads to uniform tooth loads and tooth positions so that the wear takes place uniformly over all teeth and the life time of the cutter is extended.

With the usual cutters, the height of the cutter is restricted by the occurring slop system which increases as the cut off soil must cover a greater distance to the suction mouth. The invention has the advantage that no or hardly any restrictions are imposed upon the cutter height so that always an installed cutter capacity can be optimally reached for varying types of soil by the use of cutters with various heights.

A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawings, wherein; Figure 1 is a perspective view of a cutter; Figure 2 is an end elevation looking the direction of the arrow II in Figure 1; and Figure 3 is a schematic view in longitudinal section along the line III-III of Figure 2 of the chamber which is formed between the cutter and suction mouth.

In the drawings is shown a cutter 1 which is locatable at the end of a suction tube 2a, having a suction mouth 2 and which is rotatable about its axis 3 by driving means (not shown).

On the periphery of the cutter 1 is located a plurality of cutting blades 4 extending along helical lines and comprising teeth 5 to dredge very hard soil. In addition to very hard rock like soil the cutter can also be used for hard packed sand. For very :srd soil the cutter blades are provided with replacable teeth. In the case where hard packed sand is to be dredged, the cutting blades can be provided with moulded on teeth. As represented in Figures 1 and 2, the cutting blades 4 are connected at the front of the cutter by a ring on which special teeth are provided, the tooth points of which form the outer confines of the cutter. In the preferred embodiment, said teeth are arranged on the ring at the location of the cutting blades as well as therebetween.

Depending upon the material to be dredged, the front end of the cutter can be of an open or closed construction.

The cutting blades 4 are arranged along separate helical windings between which troughs 6 are formed, which together with the cutting blades 4 define a closed peripheral surface. The soil which is broken up by the cutting blades is conducted along the troughs 6 to suction orifices 7 leading to a chamber 8 within the rear end of the cutter. The suction mouth 2 of the suction tube 2a is arranged adjacent to the chamber 8.

The suction mouth 2 can exert a strong suction force on the material to be conveyed through the chamber 8 and the troughs 6, so that a clean channel is excavated.

The inflow of water from the cutter 1 to the suction mouth 2 can be further improved by arranging a funnel-shaped flow guide 9 around the suction mouth 2, the position of which is indicated in Figure 2 by dotted lines, and of which in Figure 3 a constructive embodiment is schematically illustrated.

Preferably the suction mouth 2 should be connected directly to the orifices 7 in communication with the conveying troughs 6.

This is not possible because of the resultant "guillotine" action i.e. shearing off the dredged material of which little will ingress into the suction tube and the mixing chamber 8 is introduced, which is defined at its front end by the rear wall 12 of the cutter body wherein the orifices are formed, and at its rear side by the flow guide 9 and the adjoining closure plate 13 as schematically illustrated in Figure 3, and which serves as a guide for the material to be conveyed. Thus the mixing chamber is an integrated part of the cutter. It should be noted that in addition to the strong suction force which is exerted on the material to be conveyed, due to the rotation of the helical channels, the cutter fulfils a positive axial transport function which impels the material in the channels to the mixing chamber.The quantity of useless water which is sucked in via empty channels is thereby reduced, so that a very efficient operation is obtained.

WHAT I CLAIM IS: 1. A cutter for a cutter dredge, comprising a plurality of helically arranged cutting blades on which teeth are formed or attached in order to dredge very hard soil, wherein between the toothed cutting blades, helical troughs are formed which define with the cutting blades a substantially closed peripheral surface leading to suction orifices communicating with a chamber formed in the rear part of the cutter to which the suction mouth of a suction tube is to be connected.

2. A cutter according to claim 1 wherein the chamber is defined by a portion of the rotary cutter, one or more axially disposed non-rotary screen plates laterally of the suction mouth, and a closure plate sealed to the axial plates and suction mouth perpendicular or inclined at an acute angle to the cutter axis.

3. A cutter according to claim 1 or 2, wherein the cutter has a generally cylindrical peripheral shape.

4. A cutter according to claim 1 or 2 wherein the cutter has a generally tapering shape.

5. A cutter according to any one of claims 1 to 4 wherein the cutter is provided with a toothed nose rim.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. system which increases as the cut off soil must cover a greater distance to the suction mouth. The invention has the advantage that no or hardly any restrictions are imposed upon the cutter height so that always an installed cutter capacity can be optimally reached for varying types of soil by the use of cutters with various heights. A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawings, wherein; Figure 1 is a perspective view of a cutter; Figure 2 is an end elevation looking the direction of the arrow II in Figure 1; and Figure 3 is a schematic view in longitudinal section along the line III-III of Figure 2 of the chamber which is formed between the cutter and suction mouth. In the drawings is shown a cutter 1 which is locatable at the end of a suction tube 2a, having a suction mouth 2 and which is rotatable about its axis 3 by driving means (not shown). On the periphery of the cutter 1 is located a plurality of cutting blades 4 extending along helical lines and comprising teeth 5 to dredge very hard soil. In addition to very hard rock like soil the cutter can also be used for hard packed sand. For very :srd soil the cutter blades are provided with replacable teeth. In the case where hard packed sand is to be dredged, the cutting blades can be provided with moulded on teeth. As represented in Figures 1 and 2, the cutting blades 4 are connected at the front of the cutter by a ring on which special teeth are provided, the tooth points of which form the outer confines of the cutter. In the preferred embodiment, said teeth are arranged on the ring at the location of the cutting blades as well as therebetween. Depending upon the material to be dredged, the front end of the cutter can be of an open or closed construction. The cutting blades 4 are arranged along separate helical windings between which troughs 6 are formed, which together with the cutting blades 4 define a closed peripheral surface. The soil which is broken up by the cutting blades is conducted along the troughs 6 to suction orifices 7 leading to a chamber 8 within the rear end of the cutter. The suction mouth 2 of the suction tube 2a is arranged adjacent to the chamber 8. The suction mouth 2 can exert a strong suction force on the material to be conveyed through the chamber 8 and the troughs 6, so that a clean channel is excavated. The inflow of water from the cutter 1 to the suction mouth 2 can be further improved by arranging a funnel-shaped flow guide 9 around the suction mouth 2, the position of which is indicated in Figure 2 by dotted lines, and of which in Figure 3 a constructive embodiment is schematically illustrated. Preferably the suction mouth 2 should be connected directly to the orifices 7 in communication with the conveying troughs 6. This is not possible because of the resultant "guillotine" action i.e. shearing off the dredged material of which little will ingress into the suction tube and the mixing chamber 8 is introduced, which is defined at its front end by the rear wall 12 of the cutter body wherein the orifices are formed, and at its rear side by the flow guide 9 and the adjoining closure plate 13 as schematically illustrated in Figure 3, and which serves as a guide for the material to be conveyed. Thus the mixing chamber is an integrated part of the cutter. It should be noted that in addition to the strong suction force which is exerted on the material to be conveyed, due to the rotation of the helical channels, the cutter fulfils a positive axial transport function which impels the material in the channels to the mixing chamber.The quantity of useless water which is sucked in via empty channels is thereby reduced, so that a very efficient operation is obtained. WHAT I CLAIM IS:

1. A cutter for a cutter dredge, comprising a plurality of helically arranged cutting blades on which teeth are formed or attached in order to dredge very hard soil, wherein between the toothed cutting blades, helical troughs are formed which define with the cutting blades a substantially closed peripheral surface leading to suction orifices communicating with a chamber formed in the rear part of the cutter to which the suction mouth of a suction tube is to be connected.

2. A cutter according to claim 1 wherein the chamber is defined by a portion of the rotary cutter, one or more axially disposed non-rotary screen plates laterally of the suction mouth, and a closure plate sealed to the axial plates and suction mouth perpendicular or inclined at an acute angle to the cutter axis.

3. A cutter according to claim 1 or 2, wherein the cutter has a generally cylindrical peripheral shape.

4. A cutter according to claim 1 or 2 wherein the cutter has a generally tapering shape.

5. A cutter according to any one of claims 1 to 4 wherein the cutter is provided with a toothed nose rim.

6. A cutter according to claim 1 substan

tially as hereinbefore described with reference to the accompanying drawings.