IMPROVED SOIL CUTTING DEVICE AND DRUM WITH FORWARDLY INCLINED CUTTING ELEMENT

FIELD OF THE INVENTION

The invention relates to a device for making a vertical retaining wall and/or foundation. The invention further relates to a drum, preferably for use in the device, and a method for operating the device.

BACKGROUND

Vertical retaining walls and/or foundations can have multiple functions, they can for instance be water-retaining, soil-retaining and/or bearing. The retaining walls and/or foundations can absorb vertical loads and can also function as sheet piling for excavations in the vicinity of existing structures. Retaining walls and/or foundations can further function as quay walls or as walls in for instance tunnels or parking structures.

Two different types of device are typically used to make such vertical retaining walls and/or foundations. Use is on one hand made of a so-called slurry wall device. On the other hand, use is made of a so-called cutter soil mixing (CSM) device. The slurry wall device removes the dislodged soil and fills the formed trench with bentonite suspension for the purpose of supporting the trench walls. Reinforcement is then optionally placed in the bentonite suspension, after which the bentonite suspension is replaced by filling the trench with concrete so that the retaining walls and/or foundations are formed. The CSM device forms the retaining walls and/or foundations by mechanically mixing the dislodged soil with an injected hydraulic binding agent such as grout in situ during the dislodging. The soil with binding agent mixed in situ then hardens and forms the retaining walls and/or foundations.

The slurry wall device and the CSM device have a cutting frame. The cutting frame comprises cutting drums provided with cutting elements. The cutting drums are driven rotatingly so that the cutting elements are driven into the ground in turns. Known devices are sensitive to differing hardnesses of the soil in which the trench is being formed. A hard soil type such as sandstone banks is impossible or difficult to penetrate with known devices. The cutting elements of such known devices tend to collide with the sandstone banks in the example given. The cutting elements colliding with the sandstone banks results in an upward directed movement of the whole cutting frame with each collision of each cutting element. This jolting, upward directed movement damages the cutting devices and cutting elements. The colliding furthermore causes a deviation of a digging direction and causes a considerable increase in wear of the cutting devices and the cutting elements, and the cutting elements may even break off.

SUMMARY OF THE INVENTION

Embodiments of the invention have the object of providing a device for making a vertical retaining wall and/or foundation, which dislodges soil in improved manner. More specifically, embodiments of the invention have the object of providing a device which limits the risk of damage thereto, can be utilized in different types of ground, and is more maintenance-friendly. Embodiments of the invention further provide a drum, wherein the drum is configured to avoid damage to the device, can be utilized in different types of ground, and is more maintenance-friendly.

According to a first aspect, a device for making a vertical retaining wall and/or foundation comprises a frame with a substantially vertically movable outer end. The device further comprises a cutting frame mounted close to the outer end, wherein the cutting frame is provided with at least one pair of drums which are each rotatable about a respective rotation axis, wherein the rotation axes of the at least one pair of drums lie parallel to and at a distance from each other so that the drums can rotate adjacently of each other as seen in a plane perpendicularly of the rotation axes. An outer surface of each of the drums is provided along the periphery thereof with at least one row with at least five cutter holders extending from the outer surface in a substantially radial direction, wherein each cutter holder comprises at least one cutting element extending away from the outer surface. The cutting element has a stop surface which has an angle with a centre line which intersects the rotation axis of the corresponding drum and intersects a centre of the corresponding cutter holder at the position of the outer surface. The at least one pair of drums are rotatingly driveable for the purpose of dislodging soil while the outer end is driven into the soil.

The stop surface which has an angle with a centre line which intersects the rotation axis of the corresponding drum and a centre of the corresponding cutter holder at the position of the outer surface reduces the angle of incidence of the cutting element relative to the soil. In other words, the angle of incidence becomes more acute. This has multiple advantages. The reduced angle of incidence of the cutting element results in lower internal stress in the cutting element and the cutter holder. This increases the lifespan of the cutting element and the cutter holder. Although a resulting upward directed force is inevitable, the upward directed force is further considerably smaller. This is because the resulting upward force is directly proportional to the angle of incidence of the cutting element. When the angle of incidence decreases by providing the stop surface at an angle relative to the centre line, the upward directed force decreases. The device is therefore subjected to these harmful, jolting movements to less severe extent, whereby the lifespan increases and the time between maintenance operations becomes longer. The device can thus be utilized more, and more productively. The acute angle of incidence also allows for an improved penetration into the soil. Even in the case of harder soils, the stop surface which lies at an angle allows the cutting element to penetrate the soil with less force.

The angle is preferably greater than 5°, more preferably greater than 7°, more preferably greater than 10°.

The at least five cutting elements are preferably distributed uniformly over the same peripheral line of the outer surface. In this way each of the cutting elements dislodges a substantially uniform quantity of soil. The cutting elements are therefore also loaded uniformly, and are subjected to uniform wear. This allows maintenance of the cutting elements to take place at the same time, wherein unexpected maintenance operations are avoided.

The outer surface is preferably further provided with at least three rows with five cutter holders each, wherein the rows lie at a mutual distance as seen in a longitudinal direction of the drum, and wherein the cutter holders of adjacent rows have a mutual angle at the centre, measured between a corresponding front edge of the cutter holders. Four rows with five cutter holders each or three rows with six cutter holders each can thus be provided. When four rows with six cutter holders are provided, the mutual overlap is too great to perform maintenance on the cutting elements. It is preferred here for the number of cutter holders to be limited to five so that maintenance can be carried out in simple manner. The advantage of providing four rows is in turn based on the insight that the cutting drum can dig a wider trench. The angle at the centre is further preferably greater than 10°, more preferably greater than 15°, and is most preferably 18°. It is further noted here that a rounder cutting plane is formed with an outer surface with four rows with five cutter holders each than with an outer surface with three rows with six cutter holders each. This can be imagined by viewing the outer surface in side view and considering the cutting element on a cutter holder to be a vertex of an imaginary polygon which is oriented parallel to the side view. A polygon formed by three rows with six cutter holders each is an octadecagonal polygon. A polygon formed by four rows with five cutter holders each is an icosagonal polygon. In this way the drums, and particularly a cutting plane formed by the cutting elements, have more contact points with the soil. Although each cutting element hereby dislodges less soil, the drum as a whole will dislodge the soil more readily. Adverse jolting movements are substantially avoided in this way.

A proximal base of each cutter holder whereby the cutter holder is connected to the outer surface preferably extends along the outer surface over a minimum arc length so that a front edge of each cutter holder at least partially overlaps a rear edge of a cutter holder of an adjacent row, as seen in a plane perpendicularly of the rotation axis. An advantage hereof is based on the insight that dislodged soil co-displaces with a rotating movement of the drum. In this way the soil can be mixed. Because the cutter holders partially overlap each other, a freedom of movement of the soil is limited. The limited freedom of movement prevents dislodged soil from being pushed away. The dislodged soil is crushed better in this way, and will therefore tend to remain clumped together to lesser extent. The dislodged soil is also kept closer to the drum, whereby in situ mixing of the soil at the position of the drums is improved. The cutting frame thus digs away the soil, this in contrast to the known cutting drums which are made such that there is no overlap whatsoever, which turn over the soil under the cutter, mix this soil with cement and then lower the cutter into the liquefied soil. Owing to the lateral overlap, the cutter holders and cutting elements entrain the soil from under the drum so that space is created under the cutting frame. The soil is then entrained to a position on top of the drum and is then removed from between the cutter holders by means of the clearing plates. The mixing with a mortar thus takes place on top of the cutter owing to the clearing plates, as will be elucidated further. The cutting frame preferably further comprises at least one clearing plate between each row, wherein the clearing plate is arranged at a distance from each of the cutting elements and extends up to a maximum radial distance from the outer surface. Soil can become fixed between the rows and cause an obstruction. Such an obstruction impedes the downward movement of the cutting frame and may even wholly prevent the downward movement. The clearing plate prevents soil from blocking or obstructing the rows. The clearing plates further also realize an improve mixing of the soil. The at least one clearing plate is preferably provided at the position of a stop edge thereof with one or more protrusions.

Preferably provided on the outer surface between one or more rows are one or more teeth which extend in a substantially radial direction from the outer surface over a distance which is smaller than a maximum dimension, as measured from the outer surface, of the cutter holders. These teeth pass under the clearing plates. It is common in hard soil that the cutter holders and cutting elements dig a trench in the soil and that the hard soil remains upright between the rows. This upright soil then collides with the outer surface, whereby the drum is unable to descend further. The teeth solve this problem by cutting away the hard soil at the position of the outer surface so that the soil between the rows is pulverized and the drum is able to descend further.

Preferably provided at the position of the distal outer end of the cutter holder is a slot in which a cutting element is arrangeable. A plurality of cutting elements can further preferably also be provided in the slot or provided in a plurality of slots. A wall of the slot is provided with at least one locking groove and the cutting element comprises a passage opening which, when the cutting element is arranged in the slot, is provided to be aligned with the at least one locking groove. The cutter holder further comprises a fastening means which is provided to extend through the passage opening and the at least one locking groove in order to fix the cutting element in the cutter holder. An advantage hereof is based on the insight that in known devices a cutting element is welded to the cutter holder. Not only is the welding labour-intensive when fixing the cutting element to the cutter holder, it is also difficult to remove when replacing the cutting elements, for instance for maintenance. The formed welded connection is moreover susceptible to tearing and rust formation. The slot makes a cutting element arrangeable in simple manner. The locking groove which co-acts with the passage opening and the fastening means realizes a robust connection which can be arranged in simple manner. This simplifies maintenance of the cutting elements further.

A width of a cutter holder is preferably smaller than a width of the stop surface of the cutting element. Because the stop surface is wider than the cutter holder, only the cutting element is subjected to direct contact with soil to be dislodged. In this way the cutter holder is protected against direct contact with the solid soil. The cutter holder therefore experiences less stress during dislodging of the soil. The lifespan of the cutter holder, and particularly the drum, is improved in this way.

The cutter holders of the row lying adjacently of a base of the drum preferably comprise cutting elements, the stop surface of which protrudes beyond the base. In this way a margin between the hard soil and the drum is provided during dislodging of the soil. In this way the base of the drum is protected against direct contact with the solid soil. The margin allows the drum to be rotatable relatively freely in the soil without the drum getting stuck in the soil.

The vertically movable outer end is preferably a substantially vertical tube on which the cutting frame is mounted.

The device preferably further comprises a mortar injecting device which is provided in the cutting frame and is configured to inject a mortar between the drums during dislodging of the soil.

The at least one pair of drums are preferably rotatingly driveable in opposite direction.

Each cutter holder is preferably provided at least partially with a thickened portion at the position of a stop edge thereof, wherein the thickened portion has a width, as measured in a transverse direction, which is greater than a width of the cutter holder, preferably at least 2 mm greater, more preferably at least 4 mm. The thickened portion is more preferably provided over the whole stop edge. The advantage hereof is that the widening causes more soil to be entrained, whereby the drum digs itself into the soil. The soil is thus dragged along with the movement of the drum and removed from the bottom of the drum. The drum will hereby descend into the soil more quickly. This further has the advantage that a side wall of the cutter holders are subjected to less wear because they are in contact with the soil less during digging. This furthermore also reduces the power required for making the drum rotate.

One or more side walls of each cutter holder are preferably provided with one or more protrusions extending away from the side wall over a predetermined distance. The one or more protrusions are further preferably positioned close to the stop edge of the cutter holder. In this way soil between the cutter holders will be removed in improved manner.

According to a second aspect, the invention provides a drum, preferably for use in a device as described above, with an outer surface which is provided along the periphery thereof with at least one row with at least five cutter holders extending in a substantially radial direction from the outer surface, wherein each cutter holder comprises at least one cutting element extending away from the outer surface and having a stop surface which has an angle with a centre line which intersects the rotation axis of the corresponding drum and intersects a centre of the corresponding cutter holder at the position of the peripheral surface.

The skilled person will appreciate that advantages and objectives similar to those for the device apply for the corresponding drum, mutatis mutandis.

The angle is preferably greater than 5°, preferably greater than 7°, more preferably greater than 10°.

The at least five cutting elements are preferably positioned distributed uniformly over the same peripheral line of the outer surface.

The outer surface is preferably further provided with at least three rows, preferably four rows, with five cutter holders each, wherein the rows lie at a mutual distance as seen in a longitudinal direction of the drum, and wherein the cutter holders of adjacent rows have a mutual angle at the centre.

The angle at the centre is preferably greater than 10°, more preferably greater than 15°, and is most preferably 18°.

A base of each cutter holder, which base is connected to the outer surface, preferably extends along the outer surface over a minimum arc length so that a front edge of each cutter holder at least partially overlaps a rear edge of a cutter holder of an adjacent row, as seen in a plane transversely of the rotation axis.

Preferably provided at the position of the distal outer end of the cutter holder is a slot in which a cutting element is arrangeable, wherein a wall of the slot is provided with at least one locking groove and wherein the cutting element comprises a passage opening which, when the cutting element is arranged in the slot, is provided to be aligned with the at least one locking groove, wherein the cutter holder comprises a fastening means which is provided to extend through the passage opening and the at least one locking groove in order to fix the cutting element in the cutter holder.

A width of a cutter holder is preferably smaller than a width of the cutting element contained therein.

The cutter holders of the row adjacently of a base of the drum preferably comprise cutting elements, the stop surface of which protrudes beyond the base.

According to a third aspect, the invention provides a drum, preferably for use in a device as described above, with an outer surface which is provided along the periphery thereof with at least three rows with five cutter holders each, wherein the rows lie at a mutual distance, as seen in a longitudinal direction of the drum, and wherein the cutter holders of adjacent rows have a mutual angle at the centre.

The angle at the centre is preferably greater than 10°, more preferably greater than 15°, and is most preferably 18°.

According to the third aspect, each cutter holder preferably comprises at least one cutting element extending away from the outer surface and having a stop surface which has an angle with a centre line which intersects the rotation axis of the corresponding drum and intersects a centre of the corresponding cutter holder at the position of the peripheral surface.

According to a fourth aspect, the invention provides a method for operating a device as described above, the method comprising the following steps of:

- Rotatingly driving the at least one pair of drums in opposite direction;
- Driving the cutting frame into the soil for the purpose of dislodging the soil and digging a trench;
- Injecting a mortar between the drums during dislodging of the soil;
- Removing the cutting frame from the trench formed in the soil;
- Wherein the at least one pair of drums are driven rotatingly in the same opposite direction while being driven into the soil and removed from the trench.

A speed for driving into the soil is preferably a minimum of 30 cm/min, preferably a minimum of 40 cm/min, more preferably a minimum of 50 cm/min, for instance 60 or 85 cm/min. The method which operates the above stated device allows for unprecedented digging speeds, whereby operations can be completed considerably faster. Tests have shown digging speeds of around 130 cm/min.

The method preferably further comprises of providing at least one water buffer basin with a minimum capacity of 30 m³. A drawback of the advantageous speed is that water supply is insufficient in most situations. An average mortar mixing installation can produce only 20 to 24 m³/hour of mortar. A standpipe can produce about 20 m³/hour of water. A speed of descent of about 130 cm/min requires about 40 m³/hour of mortar. By providing a buffer basin such a speed of descent can be worked at without any significant downtime.

BRIEF DESCRIPTION OF THE FIGURES

The above and other advantageous features and objectives of the invention will become more apparent and the invention better understood with reference to the following detailed description when read in combination with the accompanying drawings, in which:

FIG. 1 a systematic front view of a device with a pair of drums;

FIG. 2 is a schematic view, as seen in a plane perpendicularly of a rotation axis of the drum, of a drum according to an embodiment with five cutter holders, each with a cutting element with a stop surface which has an angle with a centre line of the drum;

FIG. 3A is a schematic view of the drum in FIG. 2 according to a further embodiment;

FIG. 3B is a perspective view of the drum according to FIG. 3A;

FIG. 4 is a schematic section, as seen in a longitudinal direction of the drum, of a portion of a cutting frame with clearing plates according to an embodiment;

FIG. 5 is a perspective view of the device with two pairs of drums, each with four rows with five cutter holders and cutting elements according to a preferred embodiment.

The same or similar elements are designated in the drawing with the same reference numerals.

DETAILED EMBODIMENTS

The invention will now be further described on the basis of an exemplary embodiment shown in the drawing.

In the Drawing:

FIG. 1 shows a schematic front view of a device 10 for making a vertical retaining wall and/or foundation. The device 10 is preferably a cutter soil mixing (CSM) device. A CSM device has multiple advantages compared to a slurry wall device, as will be further elucidated below.

The device 10 comprises a frame 20 with a substantially vertically movable outer end. The device further comprises a cutting frame 100 mounted close to the outer end. The movable outer end is preferably a substantially vertical tube on which the cutting frame 100 is mounted. An example of such a vertical tube is a Kelly drive. The name Kelly drive refers to a type of drive which makes use of a tube with pipe section with a polygonal, for instance three-sided, four-sided, six-sided or eight-sided or grooved outer surface, which passes through a corresponding polygonal or so-called Kelly bushing. The bushing is rotated via the rotary table. In a preferred embodiment in which the device is a CSM device, the Kelly drive is the rigid connection between a pile machine and the cutting frame. The cutting frame is in this way mounted rigidly so that deviations at right angles to a downward direction of movement are avoided.

The cutting frame 100 is provided with at least one pair of drums 110, which are each rotatable about a respective rotation axis. The rotation axes of the at least one pair of drums 110 lie parallel to each other and at a distance from each other so that the drums, as seen in a plane perpendicularly of the rotation axes, can rotate adjacently of each other. The rotation axes are oriented substantially perpendicularly relative to a downward digging direction. The rotation axes preferably lie at the same height relative to a ground surface. When the drums 110 are the same size, such an arrangement prevents that a digging direction of the device deviates from a vertical direction. It will further be apparent that more than one pair of drums can be provided, use is typically made of two pairs of drums. The further pairs of drums lie parallel to each other in pairs, i.e. the rotation axes of each pair of drums lie parallel. Further pairs of drums are positioned in line with the first pair of drums. The cutting drums are designed such that adjustment is possible in a direction perpendicularly of the rotation axes of the drums. For this purpose the one drum can be rotated more slowly than the other. Even more aggressive adjustment can take place by having both drums rotate in the same direction. The cutter holders are designed such that they also retain their digging properties when rotating in opposite direction.

An outer surface 111, see FIG. 2, of each of the drums 110 is provided along the periphery thereof with at least one row with at least five cutter holders 120. The cutter holders 120 extend away from the outer surface, the cutter holders extending more specifically from the outer surface in a substantially radial direction. Each cutter holder 120 comprises at least one cutting element 130 which extends away from the outer surface. In this way the cutting elements 130 lie at a maximum distance from the rotation axis, so that the cutting elements always initiate contact with the soil before the cutter holder or drum 110. The cutting elements 130 are configured to make contact with the soil. For this purpose cutting elements 130 can be provided with one or more teeth for improving a penetration into the soil. Cutting elements 130 can further be provided with a hardened surface so that wearing of the cutting elements is slowed. Cutting elements 130 each have a stop surface 131, see FIG. 2, which has an angle α with a centre line M which intersects the rotation axis of the corresponding drum and a centre of the corresponding cutter holder at the position of the peripheral surface.

FIG. 1 further shows that the at least one pair of drums can be driven rotatingly, designated using the arrows which indicate a rotation direction. The pair of drums 110 rotate in opposite direction relative to each other. In order to correct any deviations of the drums, as seen in transverse direction of the downward movement, the two drums are rotated in the same direction. The drum 110 mounted on the left in the figure for instance rotates in clockwise direction, while the drum 110 mounted on the right in the figure rotates in counter-clockwise direction. The rotating movement of the drums 110 in conjunction with a downward movement of the outer end results in a downward directed digging movement, wherein the cutting elements 130 dislodge the soil.

FIG. 2 shows a schematic view of a drum according to an embodiment, as seen in a plane perpendicularly of a rotation axis of the drum. The drum 110 is provided with five cutter holders 120, each comprising at least one cutting element 130. FIG. 2 shows that the five cutter holders are according to a preferred embodiment distributed uniformly over the same peripheral line of outer surface 111. In this way each of the cutting elements 130 dislodges a substantially uniform quantity of soil. The cutting elements are therefore also loaded uniformly, and are subjected to uniform wear. This allows maintenance of the cutting elements to take place at the same time, wherein unexpected maintenance operations are avoided.

FIG. 2 shows that the stop surface 131 of cutting element 130 has an angle α with a centre line M which intersects the rotation axis of the drum 110 and a centre of the cutter holder 120, this comprising the respective cutting element 130, at the position of the outer periphery 111. The centre line M of the drum is a fictional line which intersects the rotation axis of the drum 110. A diameter of the drum 110 is for instance measured along the centre line M. It will be apparent that an infinite number of centre lines can be drawn through the rotation axis of the drum.

The cutter holder 120 has a proximal outer end and a distal outer end. The cutter holder 120 is connected with a base thereof to the outer surface 111 at the position of the proximal outer end. The cutter holder 120 can for instance be fixed on the outer surface by welding the base to the outer surface. The centre of the base of the cutter holder 120 at the position of the outer surface functions as second intersection of the respective centre line M. The centre line M which runs through both the rotation axis of the drum 110 and through the centre of the cutter holder 120 at the position of the peripheral surface 111 functions as reference line for determining the angle α. Although not shown, five centre lines can be drawn which intersect both the rotation axis and the centre of the base of a corresponding cutter holder 120.

The stop surface 131 of each cutting element 130 has an angle with the centre line M drawn through the centre of the corresponding cutter holder 120. The angle α is preferably greater than 5°, preferably greater than 7°, more preferably greater than 10°. In this way the cutting element is provided inclined relative to the outer surface. The cutting element 130, and more specifically the stop surface 131 thereof, is preferably inclined in accordance with a rotation direction of drum 110. In this way an angle of incidence of the cutting element 130 relative to the soil decreases. In other words, the angle of incidence becomes more acute. This has multiple advantages. The reduced angle of incidence of the cutting element 130 results in lower internal stress in the cutting element 130 and the cutter holder 120. This increases the lifespan of cutting element 130 and cutter holder 120. Although a resulting upward directed force is inevitable, the upward directed force is further considerably smaller. This is because the resulting upward force is directly proportional to the angle of incidence of the cutting element, and therefore also of the angle α. When the angle of incidence decreases by providing the stop surface 131 at an angle α relative to the centre line, the upward directed force decreases. The device, shown in FIG. 1, is therefore subjected to these harmful, jolting movements to less severe extent, whereby the lifespan increases and the time between maintenance operations becomes longer. The device can thus be utilized more productively. The acute angle of incidence also allows for an improved penetration into the soil. Even in the case of harder soils, the stop surface 131 which lies at an angle allows the cutting element to penetrate the soil with less force. Alternatively or in combination, the cutter holder can also have an angle with the centre line, see for instance FIG. 3A.

FIG. 2 further shows a preferred embodiment wherein a slot (not shown) in which a cutting element 130 can be arranged is provided at the position of the distal outer end of the cutter holder 120. The slot functions as a recess in the cutter holder 120 in which the cutting element 130 is arrangeable. A wall of the slot is provided with at least one locking groove. The locking groove can take different forms, as seen in a transverse direction thereof. The locking groove can thus have at least a partially circular cross-section or a polygonal cross-section. The cutting element 130 comprises a passage opening which, when the cutting element 130 is arranged in the slot, is provided to be aligned with at least one locking groove. A peripheral wall of the passage opening and the locking groove are therefore preferably aligned. The cutter holder 120 further comprises a fastening means 121 which is provided to extend through the passage opening and the at least one locking groove in order to fix the cutting element in the cutter holder. An example of such a fastening means 121 is for instance a pin. The fastening means 121 can be provided with a screw thread which corresponds with a screw thread in the passage opening and locking groove. The fastening means 121 can also be a knock-in pin. An advantage hereof is based on the insight that a cutting element 130 is welded to the cutter holder 130 in known devices. Not only is the welding labour-intensive when fixing the cutting element to the cutter holder 120, it is also difficult to remove when replacing the cutting elements, for instance for maintenance. The formed welded connection is moreover susceptible to tearing and rust formation. The slot makes a cutting element arrangeable in simple manner. The locking groove which co-acts with the passage opening and the fastening means realizes a connection which can be arranged and removed in simple manner. This simplifies maintenance of the cutting elements further. Alternatively, the cutting elements comprise conical, hard-metal pegs which are provided on the rear side of the cutting element with a shaft with locking ring. Such cutting elements are knocked into a slot with locking groove. The knocking action causes the locking ring to expand in the locking groove, whereby the cutting element is fixed in the cutter holder.

FIGS. 3A and 3B show respectively a schematic side view and perspective view of the drum in FIG. 2 according to a further preferred embodiment.

According to the further preferred embodiment in FIGS. 3A and 3B, the outer surface 111 of the drum 110 is further provided with at least three rows R1, R2, R3, each with six cutter holders 120/1, 120/2, 120/3, 120/4, 120/5, 120/6. These rows of cutter holders are designated as follows in the figures: the first row R1 with six cutter holders is designated with R1-120/1, . . . , R1-120/6, and so on. As shown in FIG. 3B the rows R1, R2, R3 lie at a mutual distance Xr, as seen in a longitudinal direction of the drum, i.e. measured along the rotation axis. FIGS. 3A and 3B particularly show that the cutter holders 120 of adjacent rows R1, R2, R3 have a mutual angle at the centre β. The angle at the centre β can be measured between a corresponding front edge of the cutter holders as shown in FIG. 3B or, as shown in FIG. 3A, the angle at the centre ß can be measured between a corresponding centre of the cutter holders R3-120/6; R2-120/6 at the position of outer surface 111. The angle at the centre is preferably greater than 10°, more preferably greater than 15°, and is most preferably 18°. In this way the drums 110, and particularly a cutting plane formed by the cutting elements 130, have more contact points with the soil. Although each cutting element hereby dislodges less soil, the drum as a whole will dislodge the soil more readily. Adverse jolting movements are substantially avoided in this way.

FIGS. 3A and 3B further show that the proximal base of each cutter holder 120/1, 120/2, 120/3, 120/4, 120/5, 120/6 whereby the cutter holder is connected to the outer surface 111 preferably extends along the outer surface 111 over a minimum arc length θ. In this way a front edge 122 of each cutter holder 120/1, 120/2, 120/3, 120/4, 120/5, 120/6 at least partially overlaps a rear edge 123 of a cutter holder of an adjacent row, as seen in a plane perpendicularly of the rotation axis. In FIG. 3B the front edge 122 of cutter holder 120/1 of the first row R1 overlaps a rear edge 123 of cutter holder 120/1 of the second row R2. An advantage hereof is based on the insight that dislodged soil co-displaces with a rotating movement of the drum 110. In this way the soil can be mixed. Because the cutter holders 120 partially overlap each other, a freedom of movement of the soil is limited. The limited freedom of movement prevents dislodged soil from being pushed away. The dislodged soil is crushed better in this way, and will therefore tend to remain clumped together to lesser extent. The dislodged soil is also kept closer to the drum, whereby in situ mixing of the soil at the position of the drums is improved. The cutter holders also have an angle with the centre line, measured relative to a centre line of the cutter holder itself. Such a preferred embodiment provides for a greater mutual overlap of the cutter holders.

FIG. 4 shows a schematic section, as seen in a longitudinal direction of the drum, of a portion of a cutting frame 100 with clearing plates 140 according to an embodiment.

FIG. 4 shows three rows R1, R2, R3 of cutter holders 120, each with a cutting element 130. FIG. 4 more specifically shows that a width of a cutter holder 120 is smaller than a width of the stop surface of the cutting element 130. Because the stop surface is wider than the cutter holder 120, only the cutting element is subjected to initial contact during dislodging of the soil. In this way the cutter holder is protected against direct contact with the solid soil. The cutter holder therefore experiences less stress during dislodging of the soil. The lifespan of the cutter holder, and particularly the drum, is improved in this way.

FIG. 4 further shows that the rows lie at a mutual distance Xr. The distance is preferably at least 65 mm.

Between the adjacent rows R1, R2; R2, R3 the cutting frame 100 preferably comprises at least one clearing plate 140 between each row. The clearing plate 140 is arranged at a distance from each of the cutting elements and extends up to a maximum radial distance from the outer surface 110. Soil can become fixed between the rows and cause an obstruction. Such an obstruction impedes the downward movement of the cutting frame 110 and may even wholly prevent the downward movement. The clearing plate 140 prevents the soil from blocking or obstructing the rows. Clearing plates 140 further also realize an improved mixing of the soil, particularly when the device is a CSM device. Alternatively to or in combination with clearing plates, the binding agent can also be injected between the drums under high pressure, for instance more than 200 bar. For this purpose an injecting device can be provided which injects binding agent. The injecting device can be provided on the cutting frame and comprises at least one injection nozzle per drum. The injection nozzle is directed toward the drums. In this way the drums are on the one hand cleaned by the binding agent, and binding agent is on the other hand provided for in situ hydraulic mixing with the soil. The at least one clearing plate 140 can further be provided at the position of a stop edge thereof with one or more protrusions 141. The stop edge is typically a front edge as seen in accordance with the rotation direction of the drum. The protrusions can be arranged on the front edge or on a side wall at the position of the stop edge. It is noted in this context that a stop edge need not be a sharp edge, but can also be a stop surface with a considerable width dimension. One or more side walls of each cutter holder can also be provided with one or more protrusions extending away from the side wall over a predetermined distance. By providing the protrusions soil will be removed from between rows of cutter holders 120 in improved manner.

FIG. 4 further shows that provided on the outer surface between one or more rows are one or more teeth 150 which extend in a substantially radial direction from the outer surface over a distance which is smaller than a maximum dimension, as measured from the outer surface, of the cutter holders. These teeth 150 pass under the clearing plates 140. It is common in hard soil that cutter holders 120 and cutting elements 130 dig a trench in the soil and that the hard soil remains upright between the rows. This upright soil then collides with the outer surface 111, whereby the drum 110 is unable to descend further. The teeth solve this problem by cutting away the hard soil at the position of the outer surface so that the soil between the rows is pulverized and the drum is able to descend further.

Each cutter holder 120 is preferably provided at least partially with a thickened portion at the position of a stop edge thereof, wherein the thickened portion has a width, as measured in a transverse direction, which is greater than a width of the cutter holder, preferably at least 2 mm greater, more preferably at least 4 mm. The thickened portion is more preferably provided over the whole stop edge. The advantage hereof is that the widening causes more soil to be entrained, whereby the drum digs itself into the soil. The soil is thus dragged along with the movement of the drum and removed from the bottom of the drum. The drum will hereby descend into the soil more quickly. This further has the advantage that a side wall of the cutter holders are subjected to less wear because they are in contact with the soil less during digging. This furthermore also reduces the power required for making the drum rotate.

According to the preferred embodiment in FIG. 4, the stop surface of the cutting elements lying adjacently of a base of the drum protrudes beyond the base. More specifically, the stop surfaces of the cutting elements 130 of rows R1 and R3 extend beyond the base to which they are adjacent. In this way a margin between the hard soil and the drum is provided during dislodging of the soil. In this way the base of the drum is protected against direct contact with the solid soil. The margin allows the drum to be relatively freely rotatable in the soil without the drum getting stuck in the soil.

FIG. 5 shows a perspective view of a cutting frame with four drums, the outer surface of each drum of which is provided with four rows with five cutter holders each. This has the technical advantage that maintenance of the cutting elements can be performed in considerably simpler manner. Four rows with five cutter holders each or three rows with six cutter holders each can thus be provided. When four rows with six cutter holders are provided, the mutual overlap is too great to perform maintenance on the cutting elements. It is preferred here for the number of cutter holders to be limited to five so that maintenance can be carried out in simple manner. The advantage of providing four rows is in turn based on the insight that the cutting drum can dig a wider trench, for instance a width of 800 mm with four rows with five cutter holders compared to 500 mm with three rows with six cutter holders. It is further noted here that a rounder cutting plane is formed with an outer surface with four rows with five cutter holders each than with an outer surface with three rows with six cutter holders each. This can be imagined by viewing the outer surface in side view and considering the cutting element on a cutter holder to be a vertex of an imaginary polygon which is oriented parallel to the side view. A polygon formed by three rows with six cutter holders each is an octadecagonal polygon. A polygon formed by four rows with five cutter holders each is an icosagonal polygon. FIG. 5 also illustrates the mutual overlap of the cutter holders. Owing to the lateral overlap, the cutter holders and cutting elements entrain the soil from under the drum so that space is created under the cutting frame. The soil is then entrained to a position on top of the drum and is then removed from between the cutter holders by means of the clearing plates. The mixing with a mortar thus takes place on top of the cutter owing to the clearing plates, as elucidated above. This allows for faster digging in the soil.

The skilled person will appreciate on the basis of the above description that the invention can be embodied in different ways and on the basis of different principles. The invention is not limited here to the above described embodiments. The above described embodiments and the figures are purely illustrative and serve only to increase understanding of the invention. The invention is not therefore limited to the embodiments described herein, but is defined in the claims.

IMPROVED SOIL CUTTING DEVICE AND DRUM WITH FORWARDLY INCLINED CUTTING ELEMENT

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